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passt/tcp.c
Stefano Brivio 74677bddb2 tcp: Simplify ACK accounting, skip some useless operations on tap handling 
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2021-07-26 14:23:34 +02:00

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// SPDX-License-Identifier: AGPL-3.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* tcp.c - TCP L2-L4 translation state machine
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
/**
* DOC: Theory of Operation
*
*
* PASST mode
* ==========
*
* This implementation maps TCP traffic between a single L2 interface (tap) and
* native TCP (L4) sockets, mimicking and reproducing as closely as possible the
* inferred behaviour of applications running on a guest, connected via said L2
* interface. Four connection flows are supported:
* - from the local host to the guest behind the tap interface:
* - this is the main use case for proxies in service meshes
* - we bind to configured local ports, and relay traffic between L4 sockets
* with local endpoints and the L2 interface
* - from remote hosts to the guest behind the tap interface:
* - this might be needed for services that need to be addressed directly,
* and typically configured with special port forwarding rules (which are
* not needed here)
* - we also relay traffic between L4 sockets with remote endpoints and the L2
* interface
* - from the guest to the local host:
* - this is not observed in practice, but implemented for completeness and
* transparency
* - from the guest to external hosts:
* - this might be needed for applications running on the guest that need to
* directly access internet services (e.g. NTP)
*
* Relevant goals are:
* - transparency: sockets need to behave as if guest applications were running
* directly on the host. This is achieved by:
* - avoiding port and address translations whenever possible
* - mirroring TCP dynamics by observation of socket parameters (TCP_INFO
* socket option) and TCP headers of packets coming from the tap interface,
* reapplying those parameters in both flow directions (including TCP_MSS,
* TCP_WINDOW_CLAMP socket options)
* - simplicity: only a small subset of TCP logic is implemented here and
* delegated as much as possible to the TCP implementations of guest and host
* kernel. This is achieved by:
* - avoiding a complete TCP stack reimplementation, with a modified TCP state
* machine focused on the translation of observed states instead
* - mirroring TCP dynamics as described above and hence avoiding the need for
* segmentation, explicit queueing, and reassembly of segments
* - security:
* - no dynamic memory allocation is performed
* - TODO: synflood protection
* - TODO: sequence collision attacks
*
* Portability is limited by usage of Linux-specific socket options.
*
*
* Limits
* ------
*
* To avoid the need for dynamic memory allocation, a maximum, reasonable amount
* of connections is defined by MAX_TAP_CONNS below (currently 1M, close to
* the maximum amount of file descriptors typically available to a process on
* Linux).
*
* While fragmentation and reassembly are not implemented, tracking of missing
* segments and retransmissions needs to be, thus data needs to linger on
* sockets as long as it's not acknowledged by the guest, and read using
* MSG_PEEK into a single, preallocated static buffer sized to the maximum
* supported window, 16MiB. This imposes a practical limitation on window
* scaling, that is, the maximum factor is 512. If a bigger window scaling
* factor is observed during connection establishment, connection is reset and
* reestablished by omitting the scaling factor in the SYN segment. This
* limitation only applies to the window scaling advertised by the guest, but
* if exceeded, no window scaling will be allowed at all toward either endpoint.
*
*
* Ports
* -----
*
* To avoid the need for ad-hoc configuration of port forwarding or allowed
* ports, listening sockets can be opened and bound to all unbound ports on the
* host, as far as process capabilities allow. This service needs to be started
* after any application proxy that needs to bind to local ports. Mapped ports
* can also be configured explicitly.
*
* No port translation is needed for connections initiated remotely or by the
* local host: source port from socket is reused while establishing connections
* to the guest.
*
* For connections initiated by the guest, it's not possible to force the same
* source port as connections are established by the host kernel: that's the
* only port translation needed.
*
*
* Connection tracking and storage
* -------------------------------
*
* Connections are tracked by the @tt array of struct tcp_tap_conn, containing
* addresses, ports, TCP states and parameters. This is statically allocated and
* indexed by an arbitrary connection number. The array is compacted whenever a
* connection is closed, by remapping the highest connection index in use to the
* one freed up.
*
* References used for the epoll interface report the connection index used for
* the @tt array.
*
* IPv4 addresses are stored as IPv4-mapped IPv6 addresses to avoid the need for
* separate data structures depending on the protocol version.
*
* - Inbound connection requests (to the guest) are mapped using the triple
* < source IP address, source port, destination port >
* - Outbound connection requests (from the guest) are mapped using the triple
* < destination IP address, destination port, source port >
* where the source port is the one used by the guest, not the one used by the
* corresponding host socket
*
*
* Initialisation
* --------------
*
* Up to 2^15 + 2^14 listening sockets (excluding ephemeral ports, repeated for
* IPv4 and IPv6) can be opened and bound to wildcard addresses. Some will fail
* to bind (for low ports, or ports already bound, e.g. by a proxy). These are
* added to the epoll list, with no separate storage.
*
*
* States and events
* -----------------
*
* These states apply to connected sockets only, listening sockets are always
* open after initialisation, in LISTEN state. A single state is maintained for
* both sides of the connection, and some states are omitted as they are already
* handled by host kernel and guest.
*
* - CLOSED no connection
* No associated events: this is always a final state, new connections
* directly start from TAP_SYN_SENT or SOCK_SYN_SENT described below.
*
* - TAP_SYN_SENT connect() in progress, triggered from tap
* - connect() completes SYN,ACK to tap > TAP_SYN_RCVD
* - connect() aborts RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - SOCK_SYN_SENT new connected socket, SYN sent to tap
* - SYN,ACK from tap ACK to tap > ESTABLISHED
* - socket error RST to tap, close socket > CLOSED
* - SYN,ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - TAP_SYN_RCVD connect() completed, SYN,ACK sent to tap
* - FIN from tap write shutdown > FIN_WAIT_1
* - ACK from tap > ESTABLISHED
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - ESTABLISHED connection established, ready for data
* - FIN from tap write shutdown > FIN_WAIT_1
* - zero-sized socket read read shutdown, FIN to tap > ESTABLISHED_SOCK_FIN
* - socket error RST to tap, close socket > CLOSED
* - data timeout FIN to tap > ESTABLISHED_SOCK_FIN
* - RST from tap close socket > CLOSED
*
* - ESTABLISHED_SOCK_FIN socket closing connection, FIN sent to tap
* - ACK from tap > CLOSE_WAIT
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - CLOSE_WAIT socket closing connection, ACK from tap
* - FIN from tap write shutdown > LAST_ACK
* - socket error RST to tap, close socket > CLOSED
* - FIN timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - LAST_ACK socket started close, tap completed it
* - anything from socket close socket > CLOSED
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - FIN_WAIT_1 tap closing connection, FIN sent to socket
* - zero-sized socket read FIN,ACK to tap, shutdown > FIN_WAIT_1_SOCK_FIN
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - FIN_WAIT_1_SOCK_FIN tap closing connection, FIN received from socket
* - ACK from tap close socket > CLOSED
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* Connection setup
* ----------------
*
* - inbound connection (from socket to guest): on accept() from listening
* socket, the new socket is mapped in connection tracking table, and
* three-way handshake initiated towards the guest, advertising MSS and window
* size and scaling from socket parameters
* - outbound connection (from guest to socket): on SYN segment from guest, a
* new socket is created and mapped in connection tracking table, setting
* MSS and window clamping from header and option of the observed SYN segment
*
*
* Aging and timeout
* -----------------
*
* A bitmap of TCP_MAX_CONNS bits indicate the connections subject to timed
* events based on states:
* - SOCK_SYN_SENT: after a 2MSL (240s) timeout waiting for a SYN,ACK segment
* from tap expires, connection is reset (RST to tap, socket closed)
* - TAP_SYN_RCVD: after a 2MSL (240s) timeout waiting for an ACK segment from
* tap expires, connection is reset (RST to tap, socket closed)
* - TAP_SYN_SENT: connect() is pending, timeout is handled implicitly by
* connect() timeout, connection will be reset in case
* - ESTABLISHED, ESTABLISHED_SOCK_FIN: if an ACK segment to tap is pending,
* bytes acknowledged by socket endpoint are checked every 50ms (one quarter
* of current TCP_DELACK_MAX on Linux)
* - ESTABLISHED, ESTABLISHED_SOCK_FIN: after a timeout of 3s (TODO: implement
* requirements from RFC 6298) waiting for an ACK segment from tap expires,
* data from socket queue is retransmitted starting from the last ACK sequence
* - ESTABLISHED, ESTABLISHED_SOCK_FIN: after a two hours (current
* TCP_KEEPALIVE_TIME on Linux) timeout waiting for any activity expires,
* connection is reset (RST to tap, socket closed)
* - ESTABLISHED_SOCK_FIN: after a 2MSL (240s) timeout waiting for an ACK
* segment from tap expires, connection is reset (RST to tap, socket closed)
* - CLOSE_WAIT: after a 2MSL (240s) timeout waiting for a FIN segment from tap
* expires, connection is reset (RST to tap, socket closed)
* - FIN_WAIT_1: after a 2MSL (240s) timeout waiting for an ACK segment from
* socet expires, connection is reset (RST to tap, socket closed)
* - FIN_WAIT_1_SOCK_FIN: after a 2MSL (240s) timeout waiting for an ACK segment
* from tap expires, connection is reset (RST to tap, socket closed)
* - LAST_ACK: after a 2MSL (240s) timeout waiting for an ACK segment from
* socket expires, connection is reset (RST to tap, socket closed)
*
*
* Data flows (from ESTABLISHED, ESTABLISHED_SOCK_FIN states)
* ----------------------------------------------------------
*
* @seq_to_tap: next sequence for packets to tap
* @seq_ack_from_tap: last ACK number received from tap
* @seq_from_tap: next sequence for packets from tap (not actually sent)
* @seq_ack_to_tap: last ACK number sent to tap
*
* @seq_init_from_tap: initial sequence number from tap
*
* @tap_window: last window size received from tap, scaled
* @tcpi_acked_last: most recent value of tcpi_bytes_acked (TCP_INFO)
*
* - from socket to tap:
* - on new data from socket:
* - peek into buffer
* - send data to tap:
* - starting at offset (@seq_to_tap - @seq_ack_from_tap)
* - in MSS-sized segments
* - increasing @seq_to_tap at each segment
* - up to window (until @seq_to_tap - @seq_ack_from_tap <= @tap_window)
* - mark socket in bitmap for periodic ACK check, set @last_ts_to_tap
* - on read error, send RST to tap, close socket
* - on zero read, send FIN to tap, enter ESTABLISHED_SOCK_FIN
* - on ACK from tap:
* - set @ts_ack_tap
* - check if it's the second duplicated ACK
* - consume buffer by difference between new ack_seq and @seq_ack_from_tap
* - update @seq_ack_from_tap from ack_seq in header
* - on two duplicated ACKs, reset @seq_to_tap to @seq_ack_from_tap, and
* resend with steps listed above
* - set TCP_WINDOW_CLAMP from TCP header from tap
* - on @seq_ack_from_tap == @seq_to_tap, mark in bitmap, umark otherwise
* - periodically:
* - if @seq_ack_from_tap < @seq_to_tap and the retransmission timer
* (TODO: implement requirements from RFC 6298, currently 3s fixed) from
* @ts_sock elapsed, reset @seq_to_tap to @seq_ack_from_tap, and
* resend data with the steps listed above
*
* - from tap to socket:
* - on packet from tap:
* - set @ts_tap
* - set TCP_WINDOW_CLAMP from TCP header from tap
* - check seq from header against @seq_from_tap, if data is missing, send
* two ACKs with number @seq_ack_to_tap, discard packet
* - otherwise queue data to socket, set @seq_from_tap to seq from header
* plus payload length
* - query socket for TCP_INFO, on tcpi_bytes_acked > @tcpi_acked_last,
* set @tcpi_acked_last to tcpi_bytes_acked, set @seq_ack_to_tap
* to (tcpi_bytes_acked + @seq_init_from_tap) % 2^32 and
* send ACK to tap
* - periodically:
* - query socket for TCP_INFO, on tcpi_bytes_acked > @tcpi_acked_last,
* set @tcpi_acked_last to tcpi_bytes_acked, set @seq_ack_to_tap
* to (tcpi_bytes_acked + @seq_init_from_tap) % 2^32 and
* send ACK to tap
*
*
* PASTA mode
* ==========
*
* For traffic directed to TCP ports configured for mapping to the tuntap device
* in the namespace, and for non-local traffic coming from the tuntap device,
* the implementation is identical as the PASST mode described in the previous
* section.
*
* For local traffic directed to TCP ports configured for direct mapping between
* namespaces, the implementation is substantially simpler: packets are directly
* translated between L4 sockets using a pair of splice() syscalls. These
* connections are tracked in the @ts array of struct tcp_splice_conn, using
* just four states:
*
* - CLOSED: no connection
* - SPLICE_ACCEPTED: accept() on the listening socket succeeded
* - SPLICE_CONNECT: connect() issued in the destination namespace
* - SPLICE_ESTABLISHED: connect() succeeded, packets are transferred
*/
#define _GNU_SOURCE
#include <sched.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/random.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <time.h>
#include "checksum.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
#include "siphash.h"
#include "pcap.h"
#define MAX_TAP_CONNS (128 * 1024)
#define MAX_SPLICE_CONNS (128 * 1024)
#define TCP_TAP_FRAMES 64
#define PIPE_SIZE (1024 * 1024)
#define TCP_HASH_TABLE_LOAD 70 /* % */
#define TCP_HASH_TABLE_SIZE (MAX_TAP_CONNS * 100 / \
TCP_HASH_TABLE_LOAD)
#define MAX_WS 9
#define MAX_WINDOW (1 << (16 + (MAX_WS)))
#define MSS_DEFAULT 536
#define WINDOW_DEFAULT 14600 /* RFC 6928 */
#define SYN_TIMEOUT 240000 /* ms */
#define ACK_TIMEOUT 2000
#define ACK_INTERVAL 50
#define ACT_TIMEOUT 7200000
#define FIN_TIMEOUT 240000
#define LAST_ACK_TIMEOUT 240000
/* We need to include <linux/tcp.h> for tcpi_bytes_acked, instead of
* <netinet/tcp.h>, but that doesn't include a definition for SOL_TCP
*/
#define SOL_TCP IPPROTO_TCP
enum tcp_state {
CLOSED = 0,
TAP_SYN_SENT,
SOCK_SYN_SENT,
TAP_SYN_RCVD,
ESTABLISHED,
ESTABLISHED_SOCK_FIN,
CLOSE_WAIT,
LAST_ACK,
FIN_WAIT_1,
FIN_WAIT_1_SOCK_FIN,
SPLICE_ACCEPTED,
SPLICE_CONNECT,
SPLICE_ESTABLISHED,
};
#define TCP_STATE_STR_SIZE (SPLICE_ESTABLISHED + 1)
static char *tcp_state_str[TCP_STATE_STR_SIZE] __attribute((__unused__)) = {
"CLOSED", "TAP_SYN_SENT", "SOCK_SYN_SENT", "TAP_SYN_RCVD",
"ESTABLISHED", "ESTABLISHED_SOCK_FIN", "CLOSE_WAIT", "LAST_ACK",
"FIN_WAIT_1", "FIN_WAIT_1_SOCK_FIN",
"SPLICE_ACCEPTED", "SPLICE_CONNECT", "SPLICE_ESTABLISHED",
};
#define FIN (1 << 0)
#define SYN (1 << 1)
#define RST (1 << 2)
#define ACK (1 << 4)
/* Flags for internal usage */
#define ZERO_WINDOW (1 << 5)
#define OPT_EOL 0
#define OPT_NOP 1
#define OPT_MSS 2
#define OPT_MSS_LEN 4
#define OPT_WS 3
#define OPT_WS_LEN 3
#define OPT_SACKP 4
#define OPT_SACK 5
#define OPT_TS 8
struct tcp_tap_conn;
/**
* struct tcp_tap_conn - Descriptor for a TCP connection via tap (not spliced)
* @next: Pointer to next item in hash chain, if any
* @sock: Socket descriptor number
* @hash_bucket: Bucket index in connection lookup hash table
* @a.a6: IPv6 remote address, can be IPv4-mapped
* @a.a4.zero: Zero prefix for IPv4-mapped, see RFC 6890, Table 20
* @a.a4.one: Ones prefix for IPv4-mapped
* @a.a4.a: IPv4 address
* @tap_port: Guest-facing tap port
* @sock_port: Remote, socket-facing port
* @state: TCP connection state
* @seq_to_tap: Next sequence for packets to tap
* @seq_ack_from_tap: Last ACK number received from tap
* @seq_from_tap: Next sequence for packets from tap (not actually sent)
* @seq_ack_to_tap: Last ACK number sent to tap
* @seq_init_from_tap: Initial sequence number from tap
* @tcpi_acked_last: Most recent value of tcpi_bytes_acked (TCP_INFO query)
* @ws_allowed: Window scaling allowed
* @ws: Window scaling factor
* @tap_window: Last window size received from tap, scaled
* @window_clamped: Window was clamped on socket at least once
* @no_snd_wnd: Kernel won't report window (without commit 8f7baad7f035)
* @tcpi_acked_last: Most recent value of tcpi_snd_wnd (TCP_INFO query)
* @ts_sock: Last activity timestamp from socket for timeout purposes
* @ts_tap: Last activity timestamp from tap for timeout purposes
* @ts_ack_tap: Last ACK segment timestamp from tap for timeout purposes
* @mss_guest: Maximum segment size advertised by guest
*/
struct tcp_tap_conn {
struct tcp_tap_conn *next;
int sock;
int hash_bucket;
union {
struct in6_addr a6;
struct {
uint8_t zero[10];
uint8_t one[2];
struct in_addr a;
} a4;
} a;
in_port_t tap_port;
in_port_t sock_port;
enum tcp_state state;
uint32_t seq_to_tap;
uint32_t seq_ack_from_tap;
uint32_t seq_from_tap;
uint32_t seq_ack_to_tap;
uint32_t seq_init_from_tap;
uint32_t seq_init_to_tap;
uint64_t tcpi_acked_last;
int ws_allowed;
int ws;
uint32_t tap_window;
int window_clamped;
int no_snd_wnd;
uint32_t tcpi_snd_wnd;
struct timespec ts_sock;
struct timespec ts_tap;
struct timespec ts_ack_tap;
int mss_guest;
};
/**
* struct tcp_splice_conn - Descriptor for a spliced TCP connection
* @from: File descriptor number of socket for accepted connection
* @pipe_from_to: Pipe ends for splice() from @from to @to
* @to: File descriptor number of peer connected socket
* @pipe_to_from: Pipe ends for splice() from @to to @from
* @state: TCP connection state
*/
struct tcp_splice_conn {
int from;
int pipe_from_to[2];
int to;
int pipe_to_from[2];
enum tcp_state state;
int v6;
};
/* Static buffers */
/**
* tcp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
* @psum: Partial IP header checksum (excluding tot_len and saddr)
* @psum: Partial TCP header checksum (excluding length and saddr)
* @vnet_len: 4-byte qemu vnet buffer length descriptor, only for passt mode
* @eh: Pre-filled Ethernet header
* @iph: Pre-filled IP header (except for tot_len and saddr)
* @uh: Headroom for TCP header
* @data: Storage for TCP payload
*/
__extension__ static struct tcp4_l2_buf_t {
uint32_t psum; /* 0 */
uint32_t tsum; /* 4 */
#ifdef __AVX2__
uint8_t pad[18]; /* 8, align th to 32 bytes */
#endif
uint32_t vnet_len; /* 26 */
struct ethhdr eh; /* 30 */
struct iphdr iph; /* 44 */
struct tcphdr th; /* 64 */
uint8_t data[USHRT_MAX - sizeof(struct tcphdr)];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp4_l2_buf[TCP_TAP_FRAMES] = {
[ 0 ... TCP_TAP_FRAMES - 1 ] = {
0, 0,
#ifdef __AVX2__
{ 0 },
#endif
0, L2_BUF_ETH_IP4_INIT, L2_BUF_IP4_INIT(IPPROTO_TCP),
{ .doff = sizeof(struct tcphdr) / 4, .ack = 1 }, { 0 },
},
};
static int tcp4_l2_buf_mss;
static int tcp4_l2_buf_mss_nr_set;
static int tcp4_l2_buf_mss_tap;
static int tcp4_l2_buf_mss_tap_nr_set;
/**
* tcp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
* @vnet_len: 4-byte qemu vnet buffer length descriptor, only for passt mode
* @eh: Pre-filled Ethernet header
* @ip6h: Pre-filled IP header (except for payload_len and addresses)
* @th: Headroom for TCP header
* @data: Storage for TCP payload
*/
__extension__ struct tcp6_l2_buf_t {
#ifdef __AVX2__
uint8_t pad[14]; /* 0 align ip6h to 32 bytes */
#else
uint8_t pad[2]; /* align ip6h to 4 bytes 0 */
#endif
uint32_t vnet_len; /* 14 2 */
struct ethhdr eh; /* 18 6 */
struct ipv6hdr ip6h; /* 32 20 */
struct tcphdr th; /* 72 60 */
uint8_t data[USHRT_MAX -
(sizeof(struct ipv6hdr) + sizeof(struct tcphdr))];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp6_l2_buf[TCP_TAP_FRAMES] = {
[ 0 ... TCP_TAP_FRAMES - 1 ] = {
{ 0 },
0, L2_BUF_ETH_IP6_INIT, L2_BUF_IP6_INIT(IPPROTO_TCP),
{ .doff = sizeof(struct tcphdr) / 4, .ack = 1 }, { 0 },
},
};
static int tcp6_l2_buf_mss;
static int tcp6_l2_buf_mss_nr_set;
static int tcp6_l2_buf_mss_tap;
static int tcp6_l2_buf_mss_tap_nr_set;
/* recvmmsg()/sendmmsg() data for tap */
static struct iovec tcp4_l2_iov_sock [TCP_TAP_FRAMES + 1];
static struct iovec tcp6_l2_iov_sock [TCP_TAP_FRAMES + 1];
static char tcp_buf_discard [MAX_WINDOW];
static struct iovec tcp4_l2_iov_tap [TCP_TAP_FRAMES];
static struct iovec tcp6_l2_iov_tap [TCP_TAP_FRAMES];
static struct msghdr tcp4_l2_mh_sock;
static struct msghdr tcp6_l2_mh_sock;
static struct mmsghdr tcp_l2_mh_tap [TCP_TAP_FRAMES];
/* Bitmap, activity monitoring needed for connection via tap */
static uint8_t tcp_act[MAX_TAP_CONNS / 8] = { 0 };
/* TCP connections */
static struct tcp_tap_conn tt[MAX_TAP_CONNS];
static struct tcp_splice_conn ts[MAX_SPLICE_CONNS];
/* Table for lookup from remote address, local port, remote port */
static struct tcp_tap_conn *tt_hash[TCP_HASH_TABLE_SIZE];
/**
* tcp_tap_state() - Set given TCP state for tap connection, report to stderr
* @conn: Connection pointer
* @state: New TCP state to be set
*/
static void tcp_tap_state(struct tcp_tap_conn *conn, enum tcp_state state)
{
debug("TCP: socket %i: %s -> %s",
conn->sock, tcp_state_str[conn->state], tcp_state_str[state]);
conn->state = state;
}
/**
* tcp_splice_state() - Set state for spliced connection, report to stderr
* @conn: Connection pointer
* @state: New TCP state to be set
*/
static void tcp_splice_state(struct tcp_splice_conn *conn, enum tcp_state state)
{
debug("TCP: index %i: %s -> %s",
conn - ts, tcp_state_str[conn->state], tcp_state_str[state]);
conn->state = state;
}
/**
* tcp_update_check_ip4() - Update IPv4 with variable parts from stored one
* @buf: L2 packet buffer with final IPv4 header
*/
static void tcp_update_check_ip4(struct tcp4_l2_buf_t *buf)
{
uint32_t sum = buf->psum;
sum += buf->iph.tot_len;
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 0xffff;
buf->iph.check = (uint16_t)~csum_fold(sum);
}
/**
* tcp_update_check_tcp4() - Update TCP checksum from stored one
* @buf: L2 packet buffer with final IPv4 header
*/
static void tcp_update_check_tcp4(struct tcp4_l2_buf_t *buf)
{
uint16_t tlen = ntohs(buf->iph.tot_len) - 20;
uint32_t sum = buf->tsum;
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 0xffff;
sum += htons(ntohs(buf->iph.tot_len) - 20);
buf->th.check = 0;
buf->th.check = csum(&buf->th, tlen, sum);
}
/**
* tcp_update_check_tcp6() - Calculate TCP checksum for IPv6
* @buf: L2 packet buffer with final IPv6 header
*/
static void tcp_update_check_tcp6(struct tcp6_l2_buf_t *buf)
{
int len = ntohs(buf->ip6h.payload_len) + sizeof(struct ipv6hdr);
buf->ip6h.hop_limit = IPPROTO_TCP;
buf->ip6h.version = 0;
buf->ip6h.nexthdr = 0;
buf->th.check = 0;
buf->th.check = csum(&buf->ip6h, len, 0);
buf->ip6h.hop_limit = 255;
buf->ip6h.version = 6;
buf->ip6h.nexthdr = IPPROTO_TCP;
}
/**
* tcp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
* @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/
void tcp_update_l2_buf(unsigned char *eth_d, unsigned char *eth_s,
uint32_t *ip_da)
{
int i;
for (i = 0; i < TCP_TAP_FRAMES; i++) {
struct tcp4_l2_buf_t *b4 = &tcp4_l2_buf[i];
struct tcp6_l2_buf_t *b6 = &tcp6_l2_buf[i];
if (eth_d) {
memcpy(b4->eh.h_dest, eth_d, ETH_ALEN);
memcpy(b6->eh.h_dest, eth_d, ETH_ALEN);
}
if (eth_s) {
memcpy(b4->eh.h_source, eth_s, ETH_ALEN);
memcpy(b6->eh.h_source, eth_s, ETH_ALEN);
}
if (ip_da) {
b4->iph.daddr = *ip_da;
if (!i) {
b4->iph.saddr = 0;
b4->iph.tot_len = 0;
b4->iph.check = 0;
b4->psum = sum_16b(&b4->iph, 20);
b4->tsum = ((*ip_da >> 16) & 0xffff) +
(*ip_da & 0xffff) +
htons(IPPROTO_TCP);
} else {
b4->psum = tcp4_l2_buf[0].psum;
b4->tsum = tcp4_l2_buf[0].tsum;
}
}
}
}
/**
* tcp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
*/
static void tcp_sock4_iov_init(void)
{
struct iovec *iov;
int i;
tcp4_l2_iov_sock[0].iov_base = tcp_buf_discard;
for (i = 0, iov = tcp4_l2_iov_sock + 1; i < TCP_TAP_FRAMES;
i++, iov++) {
iov->iov_base = &tcp4_l2_buf[i].data;
iov->iov_len = MSS_DEFAULT;
}
tcp4_l2_mh_sock.msg_iov = tcp4_l2_iov_sock;
for (i = 0, iov = tcp4_l2_iov_tap; i < TCP_TAP_FRAMES; i++, iov++) {
iov->iov_base = &tcp4_l2_buf[i].vnet_len;
iov->iov_len = MSS_DEFAULT;
}
}
/**
* tcp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
*/
static void tcp_sock6_iov_init(void)
{
struct iovec *iov;
int i;
tcp6_l2_iov_sock[0].iov_base = tcp_buf_discard;
for (i = 0, iov = tcp6_l2_iov_sock + 1; i < TCP_TAP_FRAMES;
i++, iov++) {
iov->iov_base = &tcp6_l2_buf[i].data;
iov->iov_len = MSS_DEFAULT;
}
tcp6_l2_mh_sock.msg_iov = tcp6_l2_iov_sock;
for (i = 0, iov = tcp6_l2_iov_tap; i < TCP_TAP_FRAMES; i++, iov++) {
iov->iov_base = &tcp6_l2_buf[i].vnet_len;
iov->iov_len = MSS_DEFAULT;
}
}
/**
* tcp_opt_get() - Get option, and value if any, from TCP header
* @th: Pointer to TCP header
* @len: Length of buffer, including TCP header
* @__type: Option type to look for
* @__optlen: Optional, filled with option length if passed
* @__value: Optional, set to start of option value if passed
*
* Return: Option value, meaningful for up to 4 bytes, -1 if not found
*/
static int tcp_opt_get(struct tcphdr *th, size_t len, uint8_t __type,
uint8_t *__optlen, char **__value)
{
uint8_t type, optlen;
char *p;
if (len > th->doff * 4)
len = th->doff * 4;
len -= sizeof(*th);
p = (char *)(th + 1);
for (; len >= 2; p += optlen, len -= optlen) {
switch (*p) {
case OPT_EOL:
return -1;
case OPT_NOP:
optlen = 1;
break;
default:
type = *(p++);
optlen = *(p++) - 2;
len -= 2;
if (type != __type)
break;
if (__optlen)
*__optlen = optlen;
if (__value)
*__value = p;
switch (optlen) {
case 0:
return 0;
case 1:
return *p;
case 2:
return ntohs(*(uint16_t *)p);
default:
return ntohl(*(uint32_t *)p);
}
}
}
return -1;
}
/**
* tcp_hash_match() - Check if a connection entry matches address and ports
* @conn: Connection entry to match against
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @tap_port: tap-facing port
* @sock_port: Socket-facing port
*
* Return: 1 on match, 0 otherwise
*/
static int tcp_hash_match(struct tcp_tap_conn *conn, int af, void *addr,
in_port_t tap_port, in_port_t sock_port)
{
if (af == AF_INET && IN6_IS_ADDR_V4MAPPED(&conn->a.a6) &&
!memcmp(&conn->a.a4.a, addr, sizeof(conn->a.a4.a)) &&
conn->tap_port == tap_port && conn->sock_port == sock_port)
return 1;
if (af == AF_INET6 &&
!memcmp(&conn->a.a6, addr, sizeof(conn->a.a6)) &&
conn->tap_port == tap_port && conn->sock_port == sock_port)
return 1;
return 0;
}
/**
* tcp_hash() - Calculate hash value for connection given address and ports
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @tap_port: tap-facing port
* @sock_port: Socket-facing port
*
* Return: hash value, already modulo size of the hash table
*/
static unsigned int tcp_hash(struct ctx *c, int af, void *addr,
in_port_t tap_port, in_port_t sock_port)
{
uint64_t b = 0;
if (af == AF_INET) {
struct {
struct in_addr addr;
in_port_t tap_port;
in_port_t sock_port;
} __attribute__((__packed__)) in = {
.addr = *(struct in_addr *)addr,
.tap_port = tap_port,
.sock_port = sock_port,
};
b = siphash_8b((uint8_t *)&in, c->tcp.hash_secret);
} else if (af == AF_INET6) {
struct {
struct in6_addr addr;
in_port_t tap_port;
in_port_t sock_port;
} __attribute__((__packed__)) in = {
.addr = *(struct in6_addr *)addr,
.tap_port = tap_port,
.sock_port = sock_port,
};
b = siphash_20b((uint8_t *)&in, c->tcp.hash_secret);
}
return (unsigned int)(b % TCP_HASH_TABLE_SIZE);
}
/**
* tcp_hash_insert() - Insert connection into hash table, chain link
* @c: Execution context
* @conn: Connection pointer
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
*/
static void tcp_hash_insert(struct ctx *c, struct tcp_tap_conn *conn,
int af, void *addr)
{
int b;
b = tcp_hash(c, af, addr, conn->tap_port, conn->sock_port);
conn->next = tt_hash[b];
tt_hash[b] = conn;
conn->hash_bucket = b;
debug("TCP: hash table insert: index %i, sock %i, bucket: %i, next: %p",
conn - tt, conn->sock, b, conn->next);
}
/**
* tcp_hash_remove() - Drop connection from hash table, chain unlink
* @conn: Connection pointer
*/
static void tcp_hash_remove(struct tcp_tap_conn *conn)
{
struct tcp_tap_conn *entry, *prev = NULL;
int b = conn->hash_bucket;
for (entry = tt_hash[b]; entry; prev = entry, entry = entry->next) {
if (entry == conn) {
if (prev)
prev->next = conn->next;
else
tt_hash[b] = conn->next;
break;
}
}
debug("TCP: hash table remove: index %i, sock %i, bucket: %i, new: %p",
conn - tt, conn->sock, b, prev ? prev->next : tt_hash[b]);
}
/**
* tcp_hash_update() - Update pointer for given connection
* @old: Old connection pointer
* @new: New connection pointer
*/
static void tcp_hash_update(struct tcp_tap_conn *old, struct tcp_tap_conn *new)
{
struct tcp_tap_conn *entry, *prev = NULL;
int b = old->hash_bucket;
for (entry = tt_hash[b]; entry; prev = entry, entry = entry->next) {
if (entry == old) {
if (prev)
prev->next = new;
else
tt_hash[b] = new;
break;
}
}
debug("TCP: hash table update: old index %i, new index %i, sock %i, "
"bucket: %i, old: %p, new: %p",
old - tt, new - tt, new->sock, b, old, new);
}
/**
* tcp_hash_lookup() - Look up connection given remote address and ports
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @tap_port: tap-facing port
* @sock_port: Socket-facing port
*
* Return: connection pointer, if found, -ENOENT otherwise
*/
static struct tcp_tap_conn *tcp_hash_lookup(struct ctx *c, int af, void *addr,
in_port_t tap_port,
in_port_t sock_port)
{
int b = tcp_hash(c, af, addr, tap_port, sock_port);
struct tcp_tap_conn *conn;
for (conn = tt_hash[b]; conn; conn = conn->next) {
if (tcp_hash_match(conn, af, addr, tap_port, sock_port))
return conn;
}
return NULL;
}
/**
* tcp_table_tap_compact - Compaction tap connection table
* @c: Execution context
* @hole: Pointer to recently closed connection
*/
static void tcp_table_tap_compact(struct ctx *c, struct tcp_tap_conn *hole)
{
union epoll_ref ref = { .proto = IPPROTO_TCP, .tcp.index = hole - tt };
struct tcp_tap_conn *from, *to;
struct epoll_event ev;
if ((hole - tt) == --c->tcp.tap_conn_count) {
bitmap_clear(tcp_act, hole - tt);
debug("TCP: hash table compaction: index %i (%p) was max index",
hole - tt, hole);
return;
}
from = &tt[c->tcp.tap_conn_count];
memcpy(hole, from, sizeof(*hole));
from->state = CLOSED;
to = hole;
tcp_hash_update(from, to);
if (to->state == SOCK_SYN_SENT)
ev.events = EPOLLRDHUP;
else if (to->state == TAP_SYN_SENT)
ev.events = EPOLLOUT | EPOLLRDHUP;
else
ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
ref.tcp.v6 = !IN6_IS_ADDR_V4MAPPED(&to->a.a6);
ref.s = from->sock;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, from->sock, &ev);
debug("TCP: hash table compaction: old index %i, new index %i, "
"sock %i, from: %p, to: %p",
from - tt, to - tt, from->sock, from, to);
}
/**
* tcp_tap_destroy() - Close tap connection, drop from hash table and epoll
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_tap_destroy(struct ctx *c, struct tcp_tap_conn *conn)
{
if (conn->state == CLOSED)
return;
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->sock, NULL);
tcp_tap_state(conn, CLOSED);
close(conn->sock);
tcp_hash_remove(conn);
tcp_table_tap_compact(c, conn);
}
static void tcp_rst(struct ctx *c, struct tcp_tap_conn *conn);
/**
* tcp_send_to_tap() - Send segment to tap, with options and values from socket
* @c: Execution context
* @conn: Connection pointer
* @flags: TCP flags to set
* @in: Payload buffer
* @len: Payload length
*
* Return: negative error code on connection reset, 0 otherwise
*/
static int tcp_send_to_tap(struct ctx *c, struct tcp_tap_conn *conn,
int flags, char *in, int len)
{
char buf[USHRT_MAX] = { 0 }, *data;
struct tcp_info info = { 0 };
socklen_t sl = sizeof(info);
struct tcphdr *th;
int ws = 0, err;
if (conn->seq_from_tap == conn->seq_ack_to_tap && !flags && len) {
err = 0;
info.tcpi_bytes_acked = conn->tcpi_acked_last;
info.tcpi_snd_wnd = conn->tcpi_snd_wnd;
info.tcpi_snd_wscale = conn->ws;
} else {
err = getsockopt(conn->sock, SOL_TCP, TCP_INFO, &info, &sl);
if (err && !(flags & RST)) {
tcp_rst(c, conn);
return err;
}
conn->tcpi_snd_wnd = info.tcpi_snd_wnd;
}
th = (struct tcphdr *)buf;
data = (char *)(th + 1);
th->doff = sizeof(*th) / 4;
if ((flags & SYN) && !err) {
/* Options: MSS, NOP and window scale if allowed (4-8 bytes) */
*data++ = OPT_MSS;
*data++ = OPT_MSS_LEN;
*(uint16_t *)data = htons(info.tcpi_snd_mss);
data += OPT_MSS_LEN - 2;
th->doff += OPT_MSS_LEN / 4;
/* Check if kernel includes commit:
* 8f7baad7f035 ("tcp: Add snd_wnd to TCP_INFO")
*/
conn->no_snd_wnd = !info.tcpi_snd_wnd;
if (conn->ws_allowed && (ws = info.tcpi_snd_wscale) &&
!conn->no_snd_wnd) {
*data++ = OPT_NOP;
*data++ = OPT_WS;
*data++ = OPT_WS_LEN;
*data++ = ws;
th->doff += (1 + OPT_WS_LEN) / 4;
}
/* RFC 793, 3.1: "[...] and the first data octet is ISN+1." */
th->seq = htonl(conn->seq_to_tap++);
} else {
th->seq = htonl(conn->seq_to_tap);
conn->seq_to_tap += len;
}
if (!err && ((info.tcpi_bytes_acked > conn->tcpi_acked_last) ||
(flags & ACK) || len)) {
th->ack = 1;
conn->seq_ack_to_tap = info.tcpi_bytes_acked +
conn->seq_init_from_tap;
if (conn->state == LAST_ACK) {
conn->seq_ack_to_tap = conn->seq_from_tap + 1;
th->seq = htonl(ntohl(th->seq) + 1);
}
th->ack_seq = htonl(conn->seq_ack_to_tap);
conn->tcpi_acked_last = info.tcpi_bytes_acked;
} else {
if (!len && !flags)
return 0;
th->ack = th->ack_seq = 0;
}
th->rst = !!(flags & RST);
th->syn = !!(flags & SYN);
th->fin = !!(flags & FIN);
th->source = htons(conn->sock_port);
th->dest = htons(conn->tap_port);
if (flags & ZERO_WINDOW) {
th->window = 0;
} else if (!err && !conn->no_snd_wnd) {
/* First value sent by receiver is not scaled */
th->window = htons(info.tcpi_snd_wnd >>
(th->syn ? 0 : info.tcpi_snd_wscale));
} else {
th->window = htons(WINDOW_DEFAULT);
}
th->urg_ptr = 0;
th->check = 0;
memcpy(data, in, len);
tap_ip_send(c, &conn->a.a6, IPPROTO_TCP, buf, th->doff * 4 + len,
conn->seq_init_to_tap);
return 0;
}
/**
* tcp_rst() - Reset a tap connection: send RST segment to tap, close socket
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_rst(struct ctx *c, struct tcp_tap_conn *conn)
{
if (conn->state == CLOSED)
return;
tcp_send_to_tap(c, conn, RST, NULL, 0);
tcp_tap_destroy(c, conn);
}
/**
* tcp_clamp_window() - Set window and scaling from option, clamp on socket
* @conn: Connection pointer
* @th: TCP header, from tap
* @len: Buffer length, at L4
* @init: Set if this is the very first segment from tap
*/
static void tcp_clamp_window(struct tcp_tap_conn *conn, struct tcphdr *th,
int len, int init)
{
if (init) {
conn->ws = tcp_opt_get(th, len, OPT_WS, NULL, NULL);
conn->ws_allowed = conn->ws >= 0 && conn->ws <= MAX_WS;
conn->ws *= conn->ws_allowed;
/* RFC 7323, 2.2: first value is not scaled. Also, don't clamp
* yet, to avoid getting a zero scale just because we set a
* small window now.
*/
conn->tap_window = ntohs(th->window);
conn->window_clamped = 0;
} else {
unsigned int window = ntohs(th->window) << conn->ws;
if (conn->window_clamped) {
if (conn->tap_window == window)
return;
/* Discard +/- 1% updates to spare some syscalls. */
if ((window > conn->tap_window &&
window * 99 / 100 < conn->tap_window) ||
(window < conn->tap_window &&
window * 101 / 100 > conn->tap_window)) {
conn->tap_window = window;
return;
}
}
conn->tap_window = window;
if (window < 256)
window = 256;
setsockopt(conn->sock, SOL_TCP, TCP_WINDOW_CLAMP,
&window, sizeof(window));
conn->window_clamped = 1;
}
}
/**
* tcp_seq_init() - Calculate initial sequence number according to RFC 6528
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @dstport: Destination port, connection-wise, network order
* @srcport: Source port, connection-wise, network order
* @now: Current timestamp
*
* Return: initial TCP sequence
*/
static uint32_t tcp_seq_init(struct ctx *c, int af, void *addr,
in_port_t dstport, in_port_t srcport,
struct timespec *now)
{
uint32_t ns, seq = 0;
if (af == AF_INET) {
struct {
struct in_addr src;
in_port_t srcport;
struct in_addr dst;
in_port_t dstport;
} __attribute__((__packed__)) in = {
.src = *(struct in_addr *)addr,
.srcport = srcport,
.dst = { c->addr4 },
.dstport = dstport,
};
seq = siphash_12b((uint8_t *)&in, c->tcp.hash_secret);
} else if (af == AF_INET6) {
struct {
struct in6_addr src;
in_port_t srcport;
struct in6_addr dst;
in_port_t dstport;
} __attribute__((__packed__)) in = {
.src = *(struct in6_addr *)addr,
.srcport = srcport,
.dst = c->addr6,
.dstport = dstport,
};
seq = siphash_36b((uint8_t *)&in, c->tcp.hash_secret);
}
ns = now->tv_sec * 1E9;
ns += now->tv_nsec >> 5; /* 32ns ticks, overflows 32 bits every 137s */
return seq + ns;
}
/**
* tcp_conn_from_tap() - Handle connection request (SYN segment) from tap
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @th: TCP header from tap
* @len: Packet length at L4
* @now: Current timestamp
*/
static void tcp_conn_from_tap(struct ctx *c, int af, void *addr,
struct tcphdr *th, size_t len,
struct timespec *now)
{
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = th->dest,
.sin_addr = *(struct in_addr *)addr,
};
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = th->dest,
.sin6_addr = *(struct in6_addr *)addr,
};
struct epoll_event ev = { .events = EPOLLIN | EPOLLET | EPOLLRDHUP };
union epoll_ref ref = { .proto = IPPROTO_TCP };
const struct sockaddr *sa;
struct tcp_tap_conn *conn;
socklen_t sl;
int s;
if (c->tcp.tap_conn_count >= MAX_TAP_CONNS)
return;
ref.s = s = socket(af, SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);
if (s < 0)
return;
conn = &tt[c->tcp.tap_conn_count++];
conn->sock = s;
conn->mss_guest = tcp_opt_get(th, len, OPT_MSS, NULL, NULL);
if (conn->mss_guest < 0)
conn->mss_guest = MSS_DEFAULT;
if (c->mode == MODE_PASST && c->v6 && conn->mss_guest > SHRT_MAX)
conn->mss_guest = SHRT_MAX;
sl = sizeof(conn->mss_guest);
setsockopt(s, SOL_TCP, TCP_MAXSEG, &conn->mss_guest, sl);
tcp_clamp_window(conn, th, len, 1);
if (af == AF_INET) {
sa = (struct sockaddr *)&addr4;
sl = sizeof(addr4);
memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero));
memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one));
memcpy(&conn->a.a4.a, addr, sizeof(conn->a.a4.a));
} else {
sa = (struct sockaddr *)&addr6;
sl = sizeof(addr6);
memcpy(&conn->a.a6, addr, sizeof(conn->a.a6));
}
conn->sock_port = ntohs(th->dest);
conn->tap_port = ntohs(th->source);
conn->ts_sock = conn->ts_tap = conn->ts_ack_tap = *now;
bitmap_set(tcp_act, conn - tt);
conn->seq_init_from_tap = ntohl(th->seq);
conn->seq_from_tap = conn->seq_init_from_tap + 1;
conn->seq_ack_to_tap = conn->seq_from_tap;
conn->seq_to_tap = tcp_seq_init(c, af, addr, th->dest, th->source, now);
conn->seq_init_to_tap = conn->seq_to_tap;
conn->seq_ack_from_tap = conn->seq_to_tap + 1;
tcp_hash_insert(c, conn, af, addr);
if (connect(s, sa, sl)) {
tcp_tap_state(conn, TAP_SYN_SENT);
if (errno != EINPROGRESS) {
tcp_rst(c, conn);
return;
}
ev.events = EPOLLOUT | EPOLLRDHUP;
} else {
tcp_tap_state(conn, TAP_SYN_RCVD);
if (tcp_send_to_tap(c, conn, SYN | ACK, NULL, 0))
return;
}
ref.tcp.index = conn - tt;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, s, &ev);
}
/**
* tcp_table_splice_compact - Compact spliced connection table
* @c: Execution context
* @hole: Pointer to recently closed connection
*/
static void tcp_table_splice_compact(struct ctx *c,
struct tcp_splice_conn *hole)
{
union epoll_ref ref_from = { .proto = IPPROTO_TCP,
.tcp.index = hole - ts };
union epoll_ref ref_to = { .proto = IPPROTO_TCP,
.tcp.index = hole - ts };
struct tcp_splice_conn *move;
struct epoll_event ev_from;
struct epoll_event ev_to;
if ((hole - ts) == --c->tcp.splice_conn_count)
return;
move = &ts[c->tcp.splice_conn_count];
memcpy(hole, move, sizeof(*hole));
move->state = CLOSED;
move = hole;
ref_from.s = move->from;
ref_from.tcp.v6 = move->v6;
ref_to.s = move->to;
ref_to.tcp.v6 = move->v6;
if (move->state == SPLICE_ACCEPTED) {
ev_from.events = ev_to.events = 0;
} else if (move->state == SPLICE_CONNECT) {
ev_from.events = EPOLLET | EPOLLRDHUP;
ev_to.events = EPOLLET | EPOLLOUT | EPOLLRDHUP;
} else {
ev_from.events = EPOLLET | EPOLLIN | EPOLLOUT | EPOLLRDHUP;
ev_to.events = EPOLLET | EPOLLIN | EPOLLOUT | EPOLLRDHUP;
}
ev_from.data.u64 = ref_from.u64;
ev_to.data.u64 = ref_to.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, move->from, &ev_from);
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, move->to, &ev_to);
}
/**
* tcp_tap_destroy() - Close spliced connection and pipes, drop from epoll
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_splice_destroy(struct ctx *c, struct tcp_splice_conn *conn)
{
switch (conn->state) {
case SPLICE_ESTABLISHED:
if (conn->pipe_from_to[0] != -1) {
close(conn->pipe_from_to[0]);
close(conn->pipe_from_to[1]);
}
if (conn->pipe_to_from[0] != -1) {
close(conn->pipe_to_from[0]);
close(conn->pipe_to_from[1]);
}
/* Falls through */
case SPLICE_CONNECT:
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->from, NULL);
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->to, NULL);
close(conn->to);
/* Falls through */
case SPLICE_ACCEPTED:
close(conn->from);
tcp_splice_state(conn, CLOSED);
tcp_table_splice_compact(c, conn);
return;
default:
return;
}
}
/**
* tcp_send_to_sock() - Send buffer to socket, update timestamp and sequence
* @c: Execution context
* @conn: Connection pointer
* @data: Data buffer
* @len: Length at L4
* @extra_flags: Additional flags for send(), if any
*
* Return: negative on socket error with connection reset, 0 otherwise
*/
static int tcp_send_to_sock(struct ctx *c, struct tcp_tap_conn *conn,
char *data, int len, int extra_flags)
{
int err = send(conn->sock, data, len,
MSG_DONTWAIT | MSG_NOSIGNAL | extra_flags);
if (err < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
tcp_send_to_tap(c, conn, ZERO_WINDOW, NULL, 0);
return err;
}
err = errno;
tcp_rst(c, conn);
return -err;
}
conn->seq_from_tap += err;
return 0;
}
/**
* tcp_sock_consume() - Consume (discard) data from buffer, update ACK sequence
* @conn: Connection pointer
* @ack_seq: ACK sequence, host order
*/
static void tcp_sock_consume(struct tcp_tap_conn *conn, uint32_t ack_seq)
{
uint32_t to_ack;
/* Implicitly take care of wrap-arounds */
to_ack = ack_seq - conn->seq_ack_from_tap;
/* Simply ignore out-of-order ACKs: we already consumed the data we
* needed from the buffer, and we won't rewind back to a lower ACK
* sequence.
*/
if (to_ack > MAX_WINDOW)
return;
if (to_ack)
recv(conn->sock, NULL, to_ack, MSG_DONTWAIT | MSG_TRUNC);
conn->seq_ack_from_tap = ack_seq;
}
/**
* tcp_data_from_sock() - Handle new data from socket, queue to tap, in window
* @c: Execution context
* @conn: Connection pointer
* @now: Current timestamp
*
* Return: negative on connection reset, 0 otherwise
*/
static int tcp_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn,
struct timespec *now)
{
int mss_tap, fill_bufs, send_bufs = 0, last_len, msg_len, iov_rem = 0;
int *buf_mss, *buf_mss_nr_set, *buf_mss_tap, *buf_mss_tap_nr_set;
int send, len, plen, v4 = IN6_IS_ADDR_V4MAPPED(&conn->a.a6);
socklen_t sl = sizeof(struct tcp_info);
struct mmsghdr *mh = tcp_l2_mh_tap;
int s = conn->sock, i, ret = 0;
struct iovec *iov, *iov_tap;
uint32_t already_sent;
struct tcp_info info;
already_sent = conn->seq_to_tap - conn->seq_ack_from_tap;
if (!conn->tap_window || already_sent >= conn->tap_window)
return 1;
fill_bufs = DIV_ROUND_UP(conn->tap_window - already_sent,
conn->mss_guest);
if (fill_bufs > TCP_TAP_FRAMES)
fill_bufs = TCP_TAP_FRAMES;
/* Adjust iovec length for recvmsg() based on what was set last time. */
if (v4) {
iov = tcp4_l2_iov_sock + 1;
buf_mss = &tcp4_l2_buf_mss;
buf_mss_nr_set = &tcp4_l2_buf_mss_nr_set;
} else {
iov = tcp6_l2_iov_sock + 1;
buf_mss = &tcp6_l2_buf_mss;
buf_mss_nr_set = &tcp6_l2_buf_mss_nr_set;
}
if (*buf_mss != conn->mss_guest) {
for (i = 0; i < fill_bufs; i++)
iov[i].iov_len = conn->mss_guest;
*buf_mss = conn->mss_guest;
*buf_mss_nr_set = fill_bufs - 1;
} else if (*buf_mss_nr_set < fill_bufs) {
for (i = *buf_mss_nr_set; i < fill_bufs; i++)
iov[i].iov_len = conn->mss_guest;
*buf_mss_nr_set = fill_bufs - 1;
}
/* First buffer is to discard data, last one may be partially filled. */
iov[-1].iov_len = already_sent;
iov_rem = (conn->tap_window - already_sent) % conn->mss_guest;
if (iov_rem && fill_bufs < TCP_TAP_FRAMES)
iov[fill_bufs - 1].iov_len = iov_rem;
if (v4)
tcp4_l2_mh_sock.msg_iovlen = fill_bufs + 1;
else
tcp6_l2_mh_sock.msg_iovlen = fill_bufs + 1;
/* Don't dequeue until acknowledged by guest. */
len = recvmsg(s, v4 ? &tcp4_l2_mh_sock : &tcp6_l2_mh_sock, MSG_PEEK);
if (len < 0)
goto err;
if (!len)
goto zero_len;
send = len - already_sent;
if (send <= 0)
goto out_restore_iov;
send_bufs = DIV_ROUND_UP(send, conn->mss_guest);
last_len = send - (send_bufs - 1) * conn->mss_guest;
/* Adjust iovec length for sending based on what was set last time. */
if (v4) {
mss_tap = conn->mss_guest +
offsetof(struct tcp4_l2_buf_t, data) -
offsetof(struct tcp4_l2_buf_t, vnet_len);
iov_tap = tcp4_l2_iov_tap;
buf_mss_tap = &tcp4_l2_buf_mss_tap;
buf_mss_tap_nr_set = &tcp4_l2_buf_mss_tap_nr_set;
} else {
mss_tap = conn->mss_guest +
offsetof(struct tcp6_l2_buf_t, data) -
offsetof(struct tcp6_l2_buf_t, vnet_len);
iov_tap = tcp6_l2_iov_tap;
buf_mss_tap = &tcp6_l2_buf_mss_tap;
buf_mss_tap_nr_set = &tcp6_l2_buf_mss_tap_nr_set;
}
if (*buf_mss_tap != mss_tap) {
for (i = 0; i < send_bufs; i++)
iov_tap[i].iov_len = mss_tap;
*buf_mss_tap = mss_tap;
*buf_mss_tap_nr_set = send_bufs;
} else if (*buf_mss_tap_nr_set < send_bufs) {
for (i = *buf_mss_tap_nr_set; i < send_bufs; i++)
iov_tap[i].iov_len = mss_tap;
*buf_mss_tap_nr_set = send_bufs;
}
iov_tap[send_bufs - 1].iov_len = mss_tap - conn->mss_guest + last_len;
/* Likely, some new data was acked too. */
if (conn->seq_from_tap != conn->seq_ack_to_tap) {
if (getsockopt(conn->sock, SOL_TCP, TCP_INFO, &info, &sl))
goto err;
conn->tcpi_acked_last = info.tcpi_bytes_acked;
conn->seq_ack_to_tap = info.tcpi_bytes_acked +
conn->seq_init_from_tap;
} else {
info.tcpi_snd_wscale = conn->ws;
info.tcpi_snd_wnd = conn->tcpi_snd_wnd;
}
if (v4)
mh->msg_hdr.msg_iov = tcp4_l2_iov_tap;
else
mh->msg_hdr.msg_iov = tcp6_l2_iov_tap;
mh->msg_hdr.msg_iovlen = 0;
plen = conn->mss_guest;
msg_len = 0;
for (i = 0; i < send_bufs; i++) {
int iov_len, ip_len;
if (i == send_bufs - 1)
plen = last_len;
if (v4) {
struct tcp4_l2_buf_t *b = &tcp4_l2_buf[i];
ip_len = plen + sizeof(struct iphdr) +
sizeof(struct tcphdr);
b->iph.tot_len = htons(ip_len);
b->iph.saddr = conn->a.a4.a.s_addr;
b->iph.daddr = c->addr4_seen;
if (!i || i == send_bufs - 1)
tcp_update_check_ip4(b);
else
b->iph.check = tcp4_l2_buf[0].iph.check;
b->th.source = htons(conn->sock_port);
b->th.dest = htons(conn->tap_port);
b->th.seq = htonl(conn->seq_to_tap);
b->th.ack_seq = htonl(conn->seq_ack_to_tap);
if (conn->no_snd_wnd) {
b->th.window = htons(WINDOW_DEFAULT);
} else {
b->th.window = htons(info.tcpi_snd_wnd >>
info.tcpi_snd_wscale);
conn->tcpi_snd_wnd = info.tcpi_snd_wnd;
}
tcp_update_check_tcp4(b);
if (c->mode == MODE_PASTA) {
ip_len += sizeof(struct ethhdr);
write(c->fd_tap, &b->eh, ip_len);
pcap((char *)&b->eh, ip_len);
conn->seq_to_tap += plen;
continue;
}
b->vnet_len = htonl(sizeof(struct ethhdr) + ip_len);
} else {
struct tcp6_l2_buf_t *b = &tcp6_l2_buf[i];
uint32_t flow = conn->seq_init_to_tap;
ip_len = plen + sizeof(struct ipv6hdr) +
sizeof(struct tcphdr);
b->ip6h.payload_len = htons(plen +
sizeof(struct tcphdr));
b->ip6h.saddr = conn->a.a6;
if (IN6_IS_ADDR_LINKLOCAL(&b->ip6h.saddr))
b->ip6h.daddr = c->addr6_ll_seen;
else
b->ip6h.daddr = c->addr6_seen;
b->th.source = htons(conn->sock_port);
b->th.dest = htons(conn->tap_port);
b->th.seq = htonl(conn->seq_to_tap);
b->th.ack_seq = htonl(conn->seq_ack_to_tap);
if (conn->no_snd_wnd) {
b->th.window = htons(WINDOW_DEFAULT);
} else {
b->th.window = htons(info.tcpi_snd_wnd >>
info.tcpi_snd_wscale);
conn->tcpi_snd_wnd = info.tcpi_snd_wnd;
}
memset(b->ip6h.flow_lbl, 0, 3);
tcp_update_check_tcp6(b);
b->ip6h.flow_lbl[0] = (flow >> 16) & 0xf;
b->ip6h.flow_lbl[1] = (flow >> 8) & 0xff;
b->ip6h.flow_lbl[2] = (flow >> 0) & 0xff;
if (c->mode == MODE_PASTA) {
ip_len += sizeof(struct ethhdr);
write(c->fd_tap, &b->eh, ip_len);
pcap((char *)&b->eh, ip_len);
conn->seq_to_tap += plen;
continue;
}
b->vnet_len = htonl(sizeof(struct ethhdr) + ip_len);
}
iov_len = sizeof(uint32_t) + sizeof(struct ethhdr) + ip_len;
/* Switch to a new message if this one is too long for qemu. */
if (msg_len && msg_len + iov_len > SHRT_MAX) {
mh++;
mh->msg_hdr.msg_iovlen = 0;
msg_len = 0;
if (v4)
mh->msg_hdr.msg_iov = &tcp4_l2_iov_tap[i];
else
mh->msg_hdr.msg_iov = &tcp6_l2_iov_tap[i];
}
mh->msg_hdr.msg_iovlen++;
msg_len += iov_len;
conn->seq_to_tap += plen;
}
if (c->mode == MODE_PASTA)
goto out;
sendmmsg(c->fd_tap, tcp_l2_mh_tap, mh - tcp_l2_mh_tap + 1,
MSG_NOSIGNAL | MSG_DONTWAIT);
pcapmm(tcp_l2_mh_tap, mh - tcp_l2_mh_tap + 1);
goto out;
err:
if (errno != EAGAIN && errno != EWOULDBLOCK) {
tcp_rst(c, conn);
ret = -errno;
}
goto out_restore_iov;
zero_len:
if (conn->state >= ESTABLISHED_SOCK_FIN)
goto out_restore_iov;
tcp_tap_state(conn, ESTABLISHED_SOCK_FIN);
tcp_send_to_tap(c, conn, FIN | ACK, NULL, 0);
goto out_restore_iov;
out:
conn->ts_sock = *now;
out_restore_iov:
if (iov_rem)
iov[fill_bufs - 1].iov_len = conn->mss_guest;
if (send_bufs)
iov_tap[send_bufs - 1].iov_len = mss_tap;
return ret;
}
/**
* tcp_tap_handler() - Handle packets from tap and state transitions
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Destination address
* @msg: Input messages
* @count: Message count
* @now: Current timestamp
*
* Return: count of consumed packets
*/
int tcp_tap_handler(struct ctx *c, int af, void *addr,
struct tap_msg *msg, int count, struct timespec *now)
{
union epoll_ref ref = { .proto = IPPROTO_TCP,
.tcp.v6 = ( af == AF_INET6 ) };
/* TODO: Implement message batching for TCP */
struct tcphdr *th = (struct tcphdr *)msg[0].l4h;
size_t len = msg[0].l4_len;
uint32_t ack_seq;
struct tcp_tap_conn *conn;
struct epoll_event ev;
size_t off, skip = 0;
int ws, i;
if (len < sizeof(*th))
return 1;
off = th->doff * 4;
if (off < sizeof(*th) || off > len)
return 1;
conn = tcp_hash_lookup(c, af, addr, htons(th->source), htons(th->dest));
if (!conn) {
if (th->syn && !th->ack)
tcp_conn_from_tap(c, af, addr, th, len, now);
return 1;
}
/* TODO: Partial ACK coalescing, merge with message coalescing */
ack_seq = ntohl(th->ack_seq);
for (i = 0; conn->state == ESTABLISHED && i < count; i++) {
struct tcphdr *__th = (struct tcphdr *)msg[i].l4h;
size_t __len = msg[i].l4_len;
if (__len < sizeof(*th))
break;
off = __th->doff * 4;
if (off < sizeof(*th) || off > __len)
break;
if (!th->ack)
continue;
if (ntohl(th->ack_seq) - ack_seq < MAX_WINDOW)
ack_seq = ntohl(th->ack_seq);
}
if (th->rst) {
tcp_tap_destroy(c, conn);
return 1;
}
if (count == 1)
tcp_clamp_window(conn, th, len, th->syn && th->ack);
conn->ts_tap = *now;
if (ntohl(th->seq) < conn->seq_from_tap &&
conn->seq_from_tap - ntohl(th->seq) < MAX_WINDOW) {
skip = conn->seq_from_tap - ntohl(th->seq);
}
switch (conn->state) {
case SOCK_SYN_SENT:
if (!th->syn || !th->ack) {
tcp_rst(c, conn);
return 1;
}
conn->mss_guest = tcp_opt_get(th, len, OPT_MSS, NULL, NULL);
if (conn->mss_guest < 0)
conn->mss_guest = MSS_DEFAULT;
/* Don't upset qemu */
if (c->mode == MODE_PASST && c->v6 &&
conn->mss_guest > SHRT_MAX)
conn->mss_guest = SHRT_MAX;
ws = tcp_opt_get(th, len, OPT_WS, NULL, NULL);
if (ws > MAX_WS) {
if (tcp_send_to_tap(c, conn, RST, NULL, 0))
return 1;
conn->seq_to_tap = 0;
conn->ws_allowed = 0;
tcp_send_to_tap(c, conn, SYN, NULL, 0);
return 1;
}
/* info.tcpi_bytes_acked already includes one byte for SYN, but
* not for incoming connections.
*/
conn->seq_init_from_tap = ntohl(th->seq) + 1;
conn->seq_from_tap = conn->seq_init_from_tap;
conn->seq_ack_to_tap = conn->seq_from_tap;
tcp_tap_state(conn, ESTABLISHED);
tcp_send_to_tap(c, conn, ACK, NULL, 0);
/* The client might have sent data already, which we didn't
* dequeue waiting for SYN,ACK from tap -- check now.
*/
tcp_data_from_sock(c, conn, now);
ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
ref.s = conn->sock;
ref.tcp.index = conn - tt;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->sock, &ev);
break;
case TAP_SYN_RCVD:
if (th->fin) {
shutdown(conn->sock, SHUT_WR);
tcp_tap_state(conn, FIN_WAIT_1);
break;
}
if (!th->ack) {
tcp_rst(c, conn);
return 1;
}
tcp_tap_state(conn, ESTABLISHED);
break;
case ESTABLISHED:
case ESTABLISHED_SOCK_FIN:
conn->ts_ack_tap = *now;
if (ntohl(th->ack_seq) > conn->seq_to_tap &&
(conn->seq_to_tap - ntohl(th->ack_seq)) > MAX_WINDOW) {
return count;
}
if (th->ack) {
if (count == 1)
tcp_sock_consume(conn, ack_seq);
if (conn->state == ESTABLISHED_SOCK_FIN) {
if (!tcp_data_from_sock(c, conn, now))
tcp_tap_state(conn, CLOSE_WAIT);
}
}
if (ntohl(th->seq) > conn->seq_from_tap) {
tcp_send_to_tap(c, conn, ACK, NULL, 0);
tcp_send_to_tap(c, conn, ACK, NULL, 0);
return count;
}
if (skip < len - off &&
tcp_send_to_sock(c, conn,
msg[0].l4h + off + skip, len - off - skip,
(count > 1) ? MSG_MORE : 0))
return 1;
if (count == 1)
tcp_send_to_tap(c, conn, ACK, NULL, 0);
if (th->fin) {
shutdown(conn->sock, SHUT_WR);
if (conn->state == ESTABLISHED)
tcp_tap_state(conn, FIN_WAIT_1);
else
tcp_tap_state(conn, LAST_ACK);
}
break;
case CLOSE_WAIT:
tcp_sock_consume(conn, ntohl(th->ack_seq));
if (skip < (len - off) &&
tcp_send_to_sock(c, conn,
msg[0].l4h + off + skip, len - off - skip,
th->psh ? 0 : MSG_MORE))
break;
if (th->fin) {
shutdown(conn->sock, SHUT_WR);
tcp_tap_state(conn, LAST_ACK);
}
break;
case FIN_WAIT_1_SOCK_FIN:
if (th->ack)
tcp_tap_destroy(c, conn);
break;
case FIN_WAIT_1:
case TAP_SYN_SENT:
case LAST_ACK:
case SPLICE_ACCEPTED:
case SPLICE_CONNECT:
case SPLICE_ESTABLISHED:
case CLOSED: /* ;) */
break;
}
return 1;
}
/**
* tcp_connect_finish() - Handle completion of connect() from EPOLLOUT event
* @c: Execution context
* @s: File descriptor number for socket
* @ref: epoll reference
*/
static void tcp_connect_finish(struct ctx *c, struct tcp_tap_conn *conn,
union epoll_ref ref)
{
struct epoll_event ev;
socklen_t sl;
int so;
sl = sizeof(so);
if (getsockopt(conn->sock, SOL_SOCKET, SO_ERROR, &so, &sl) || so) {
tcp_rst(c, conn);
return;
}
if (tcp_send_to_tap(c, conn, SYN | ACK, NULL, 0))
return;
/* Drop EPOLLOUT, only used to wait for connect() to complete */
ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->sock, &ev);
tcp_tap_state(conn, TAP_SYN_RCVD);
}
/**
* tcp_splice_connect_finish() - Completion of connect() or call on success
* @c: Execution context
* @conn: Connection pointer
* @v6: Set on IPv6 connection
*/
static void tcp_splice_connect_finish(struct ctx *c,
struct tcp_splice_conn *conn, int v6)
{
union epoll_ref ref_from = { .proto = IPPROTO_TCP, .s = conn->from,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
union epoll_ref ref_to = { .proto = IPPROTO_TCP, .s = conn->to,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
struct epoll_event ev_from, ev_to;
if (conn->state == SPLICE_CONNECT) {
socklen_t sl;
int so;
sl = sizeof(so);
if (getsockopt(conn->to, SOL_SOCKET, SO_ERROR, &so, &sl) ||
so) {
tcp_splice_destroy(c, conn);
return;
}
tcp_splice_state(conn, SPLICE_ESTABLISHED);
ev_from.events = ev_to.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
ev_from.data.u64 = ref_from.u64;
ev_to.data.u64 = ref_to.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->from, &ev_from);
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->to, &ev_to);
}
conn->pipe_from_to[0] = conn->pipe_to_from[0] = -1;
if (pipe2(conn->pipe_to_from, O_NONBLOCK) ||
pipe2(conn->pipe_from_to, O_NONBLOCK)) {
tcp_splice_destroy(c, conn);
return;
}
fcntl(conn->pipe_from_to[0], F_SETPIPE_SZ, PIPE_SIZE);
fcntl(conn->pipe_to_from[0], F_SETPIPE_SZ, PIPE_SIZE);
}
/**
* tcp_splice_connect() - Create and connect socket for new spliced connection
* @c: Execution context
* @conn: Connection pointer
* @v6: Set on IPv6 connection
* @port: Destination port, host order
*
* Return: 0 for connect() succeeded or in progress, negative value on error
*/
static int tcp_splice_connect(struct ctx *c, struct tcp_splice_conn *conn,
int v6, in_port_t port)
{
int sock_conn = socket(v6 ? AF_INET6 : AF_INET,
SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);
union epoll_ref ref_accept = { .proto = IPPROTO_TCP, .s = conn->from,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
union epoll_ref ref_conn = { .proto = IPPROTO_TCP, .s = sock_conn,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
struct epoll_event ev_accept = { .events = EPOLLRDHUP | EPOLLET,
.data.u64 = ref_accept.u64 };
struct epoll_event ev_conn = { .events = EPOLLRDHUP | EPOLLET,
.data.u64 = ref_conn.u64 };
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = htons(port),
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
};
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = htons(port),
.sin_addr = { .s_addr = htonl(INADDR_LOOPBACK) },
};
const struct sockaddr *sa;
int ret, one = 1;
socklen_t sl;
if (sock_conn < 0)
return -errno;
conn->to = sock_conn;
setsockopt(conn->from, SOL_TCP, TCP_CORK, &one, sizeof(one));
setsockopt(conn->from, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
setsockopt(conn->to, SOL_TCP, TCP_CORK, &one, sizeof(one));
setsockopt(conn->to, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
if (v6) {
sa = (struct sockaddr *)&addr6;
sl = sizeof(addr6);
} else {
sa = (struct sockaddr *)&addr4;
sl = sizeof(addr4);
}
if (connect(conn->to, sa, sl)) {
if (errno != EINPROGRESS) {
ret = -errno;
close(sock_conn);
return ret;
}
tcp_splice_state(conn, SPLICE_CONNECT);
ev_conn.events |= EPOLLOUT;
} else {
tcp_splice_state(conn, SPLICE_ESTABLISHED);
tcp_splice_connect_finish(c, conn, v6);
ev_conn.events |= EPOLLIN;
ev_accept.events |= EPOLLIN;
}
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->from, &ev_accept);
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->to, &ev_conn);
return 0;
}
/**
* struct tcp_splice_connect_ns_arg - Arguments for tcp_splice_connect_ns()
* @c: Execution context
* @conn: Accepted inbound connection
* @v6: Set for inbound IPv6 connection
* @port: Destination port, host order
* @ret: Return value of tcp_splice_connect_ns()
*/
struct tcp_splice_connect_ns_arg {
struct ctx *c;
struct tcp_splice_conn *conn;
int v6;
in_port_t port;
int ret;
};
/**
* tcp_splice_connect_ns() - Enter namespace and call tcp_splice_connect()
* @arg: See struct tcp_splice_connect_ns_arg
*
* Return: 0
*/
static int tcp_splice_connect_ns(void *arg)
{
struct tcp_splice_connect_ns_arg *a;
a = (struct tcp_splice_connect_ns_arg *)arg;
ns_enter(a->c->pasta_pid);
a->ret = tcp_splice_connect(a->c, a->conn, a->v6, a->port);
return 0;
}
/**
* tcp_splice_new() - Handle new inbound, spliced connection
* @c: Execution context
* @conn: Connection pointer
* @v6: Set for IPv6 connection
* @port: Destination port, host order
*
* Return: return code from connect()
*/
static int tcp_splice_new(struct ctx *c, struct tcp_splice_conn *conn,
int v6, in_port_t port)
{
struct tcp_splice_connect_ns_arg ns_arg = { c, conn, v6, port, 0 };
char ns_fn_stack[NS_FN_STACK_SIZE];
if ((!v6 && bitmap_isset(c->tcp.port4_to_ns, port)) ||
(v6 && bitmap_isset(c->tcp.port6_to_ns, port))) {
clone(tcp_splice_connect_ns,
ns_fn_stack + sizeof(ns_fn_stack) / 2,
CLONE_VM | CLONE_VFORK | CLONE_FILES | SIGCHLD,
(void *)&ns_arg);
return ns_arg.ret;
}
return tcp_splice_connect(c, conn, v6, port);
}
/**
* tcp_conn_from_sock() - Handle new connection request from listening socket
* @c: Execution context
* @ref: epoll reference of listening socket
* @now: Current timestamp
*/
static void tcp_conn_from_sock(struct ctx *c, union epoll_ref ref,
struct timespec *now)
{
union epoll_ref ref_conn = { .proto = IPPROTO_TCP,
.tcp.v6 = ref.tcp.v6 };
struct sockaddr_storage sa;
struct tcp_tap_conn *conn;
struct epoll_event ev;
socklen_t sa_len;
int s;
if (c->tcp.tap_conn_count >= MAX_TAP_CONNS)
return;
sa_len = sizeof(sa);
s = accept4(ref.s, (struct sockaddr *)&sa, &sa_len, SOCK_NONBLOCK);
if (s < 0)
return;
conn = &tt[c->tcp.tap_conn_count++];
ref_conn.tcp.index = conn - tt;
ref_conn.s = conn->sock = s;
if (ref.tcp.v6) {
struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)&sa;
if (IN6_IS_ADDR_LOOPBACK(&sa6->sin6_addr) ||
!memcmp(&sa6->sin6_addr, &c->addr6_seen, sizeof(c->addr6)))
memcpy(&sa6->sin6_addr, &c->gw6, sizeof(c->gw6));
memcpy(&conn->a.a6, &sa6->sin6_addr, sizeof(conn->a.a6));
conn->sock_port = ntohs(sa6->sin6_port);
conn->tap_port = ref.tcp.index;
conn->seq_to_tap = tcp_seq_init(c, AF_INET6, &sa6->sin6_addr,
conn->sock_port,
conn->tap_port,
now);
conn->seq_init_to_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn, AF_INET6, &sa6->sin6_addr);
} else {
struct sockaddr_in *sa4 = (struct sockaddr_in *)&sa;
memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero));
memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one));
if (ntohl(sa4->sin_addr.s_addr) == INADDR_LOOPBACK ||
ntohl(sa4->sin_addr.s_addr) == INADDR_ANY ||
sa4->sin_addr.s_addr == c->addr4_seen)
sa4->sin_addr.s_addr = c->gw4;
memcpy(&conn->a.a4.a, &sa4->sin_addr, sizeof(conn->a.a4.a));
conn->sock_port = ntohs(sa4->sin_port);
conn->tap_port = ref.tcp.index;
conn->seq_to_tap = tcp_seq_init(c, AF_INET, &sa4->sin_addr,
conn->sock_port,
conn->tap_port,
now);
conn->seq_init_to_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn, AF_INET, &sa4->sin_addr);
}
conn->seq_ack_from_tap = conn->seq_to_tap + 1;
conn->tap_window = WINDOW_DEFAULT;
conn->ws_allowed = 1;
conn->ts_sock = conn->ts_tap = conn->ts_ack_tap = *now;
bitmap_set(tcp_act, conn - tt);
ev.events = EPOLLRDHUP;
ev.data.u64 = ref_conn.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->sock, &ev);
tcp_tap_state(conn, SOCK_SYN_SENT);
tcp_send_to_tap(c, conn, SYN, NULL, 0);
}
/**
* tcp_sock_handler_splice() - Handler for socket mapped to spliced connection
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
*/
void tcp_sock_handler_splice(struct ctx *c, union epoll_ref ref,
uint32_t events)
{
int move_from, move_to, *pipes;
struct tcp_splice_conn *conn;
if (ref.tcp.listen) {
int s;
if (c->tcp.splice_conn_count >= MAX_SPLICE_CONNS)
return;
if ((s = accept4(ref.s, NULL, NULL, SOCK_NONBLOCK)) < 0)
return;
conn = &ts[c->tcp.splice_conn_count++];
conn->from = s;
tcp_splice_state(conn, SPLICE_ACCEPTED);
if (tcp_splice_new(c, conn, ref.tcp.v6, ref.tcp.index))
tcp_splice_destroy(c, conn);
return;
}
conn = &ts[ref.tcp.index];
if (events & EPOLLRDHUP || events & EPOLLHUP || events & EPOLLERR) {
tcp_splice_destroy(c, conn);
return;
}
if (events & EPOLLOUT) {
struct epoll_event ev = {
.events = EPOLLIN | EPOLLET | EPOLLRDHUP,
.data.u64 = ref.u64,
};
if (conn->state == SPLICE_CONNECT) {
tcp_splice_connect_finish(c, conn, ref.tcp.v6);
return;
}
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, ref.s, &ev);
move_to = ref.s;
if (ref.s == conn->to) {
move_from = conn->from;
pipes = conn->pipe_from_to;
} else {
move_from = conn->to;
pipes = conn->pipe_to_from;
}
} else {
move_from = ref.s;
if (ref.s == conn->from) {
move_to = conn->to;
pipes = conn->pipe_from_to;
} else {
move_to = conn->from;
pipes = conn->pipe_to_from;
}
}
swap:
while (1) {
int retry_write = 1, no_read = 1;
ssize_t ret, nr = 0, nw;
retry:
ret = splice(move_from, NULL, pipes[1], NULL, PIPE_SIZE,
SPLICE_F_MOVE);
if (ret < 0) {
if (errno == EAGAIN) {
nr = PIPE_SIZE;
} else {
tcp_splice_destroy(c, conn);
return;
}
} else if (!ret && no_read) {
break;
} else if (ret) {
no_read = 0;
nr += ret;
}
nw = splice(pipes[0], NULL, move_to, NULL, nr, SPLICE_F_MOVE);
if (nw < 0) {
if (errno == EAGAIN) {
struct epoll_event ev = {
.events = EPOLLIN | EPOLLOUT | EPOLLET |
EPOLLRDHUP
};
if (no_read)
break;
if (retry_write--)
goto retry;
ref.s = move_to;
ev.data.u64 = ref.u64,
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, move_to,
&ev);
break;
}
tcp_splice_destroy(c, conn);
return;
}
}
if ((events & (EPOLLIN | EPOLLOUT)) == (EPOLLIN | EPOLLOUT)) {
events = EPOLLIN;
SWAP(move_from, move_to);
if (pipes == conn->pipe_from_to)
pipes = conn->pipe_to_from;
else
pipes = conn->pipe_from_to;
goto swap;
}
}
/**
* tcp_sock_handler() - Handle new data from socket
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
* @now: Current timestamp
*/
void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
struct timespec *now)
{
struct tcp_tap_conn *conn;
if (ref.tcp.splice) {
tcp_sock_handler_splice(c, ref, events);
return;
}
if (ref.tcp.listen) {
tcp_conn_from_sock(c, ref, now);
return;
}
conn = &tt[ref.tcp.index];
if (conn->state == LAST_ACK) {
tcp_send_to_tap(c, conn, ACK, NULL, 0);
tcp_tap_destroy(c, conn);
return;
}
if (conn->state == SOCK_SYN_SENT) {
/* This can only be a socket error or a shutdown from remote */
tcp_rst(c, conn);
return;
}
if (events & EPOLLERR) {
if (conn->state != CLOSED)
tcp_rst(c, conn);
return;
}
if (events & EPOLLOUT) { /* Implies TAP_SYN_SENT */
tcp_connect_finish(c, conn, ref);
return;
}
if (conn->state == ESTABLISHED)
tcp_data_from_sock(c, conn, now);
if (events & (EPOLLRDHUP | EPOLLHUP)) {
if (conn->state == ESTABLISHED) {
tcp_tap_state(conn, ESTABLISHED_SOCK_FIN);
shutdown(conn->sock, SHUT_RD);
tcp_data_from_sock(c, conn, now);
tcp_send_to_tap(c, conn, FIN | ACK, NULL, 0);
} else if (conn->state == FIN_WAIT_1) {
tcp_tap_state(conn, FIN_WAIT_1_SOCK_FIN);
shutdown(conn->sock, SHUT_RD);
tcp_data_from_sock(c, conn, now);
tcp_send_to_tap(c, conn, FIN | ACK, NULL, 0);
tcp_sock_consume(conn, conn->seq_ack_from_tap);
} else {
tcp_tap_destroy(c, conn);
}
}
}
/**
* tcp_sock_init_ns() - Bind sockets in namespace for inbound connections
* @arg: Execution context
*
* Return: 0 on success, -1 on failure
*/
static int tcp_sock_init_ns(void *arg)
{
union tcp_epoll_ref tref = { .listen = 1, .splice = 1 };
struct ctx *c = (struct ctx *)arg;
in_port_t port;
ns_enter(c->pasta_pid);
if (c->v4) {
tref.v6 = 0;
for (port = 0; port < USHRT_MAX; port++) {
if (!bitmap_isset(c->tcp.port4_to_init, port))
continue;
tref.index = port;
sock_l4(c, AF_INET, IPPROTO_TCP, port, BIND_LOOPBACK,
tref.u32);
}
}
if (c->v6) {
tref.v6 = 1;
for (port = 0; port < USHRT_MAX; port++) {
if (!bitmap_isset(c->tcp.port6_to_init, port))
continue;
tref.index = port;
sock_l4(c, AF_INET6, IPPROTO_TCP, port, BIND_LOOPBACK,
tref.u32);
}
}
return 0;
}
/**
* tcp_sock_init() - Bind sockets for inbound connections, get key for sequence
* @c: Execution context
*
* Return: 0 on success, -1 on failure
*/
int tcp_sock_init(struct ctx *c)
{
union tcp_epoll_ref tref = { .listen = 1 };
char ns_fn_stack[NS_FN_STACK_SIZE];
enum bind_type tap_bind;
in_port_t port;
getrandom(&c->tcp.hash_secret, sizeof(c->tcp.hash_secret), GRND_RANDOM);
if (c->v4) {
tref.v6 = 0;
for (port = 0; port < USHRT_MAX; port++) {
tref.index = port;
if (bitmap_isset(c->tcp.port4_to_ns, port)) {
tref.splice = 1;
sock_l4(c, AF_INET, IPPROTO_TCP, port,
BIND_LOOPBACK, tref.u32);
tap_bind = BIND_EXT;
} else {
tap_bind = BIND_ANY;
}
if (bitmap_isset(c->tcp.port4_to_tap, port)) {
tref.splice = 0;
sock_l4(c, AF_INET, IPPROTO_TCP, port,
tap_bind, tref.u32);
}
}
tcp_sock4_iov_init();
}
if (c->v6) {
tref.v6 = 1;
for (port = 0; port < USHRT_MAX; port++) {
tref.index = port;
if (bitmap_isset(c->tcp.port6_to_ns, port)) {
tref.splice = 1;
sock_l4(c, AF_INET6, IPPROTO_TCP, port,
BIND_LOOPBACK, tref.u32);
tap_bind = BIND_EXT;
} else {
tap_bind = BIND_ANY;
}
if (bitmap_isset(c->tcp.port6_to_tap, port)) {
tref.splice = 0;
sock_l4(c, AF_INET6, IPPROTO_TCP, port,
tap_bind, tref.u32);
}
}
tcp_sock6_iov_init();
}
if (c->mode == MODE_PASTA) {
clone(tcp_sock_init_ns, ns_fn_stack + sizeof(ns_fn_stack) / 2,
CLONE_VM | CLONE_VFORK | CLONE_FILES | SIGCHLD,
(void *)c);
}
return 0;
}
/**
* tcp_timer_one() - Handler for timed events on one socket
* @c: Execution context
* @conn: Connection pointer
* @ts: Timestamp from caller
*/
static void tcp_timer_one(struct ctx *c, struct tcp_tap_conn *conn,
struct timespec *ts)
{
int ack_tap_ms = timespec_diff_ms(ts, &conn->ts_ack_tap);
int sock_ms = timespec_diff_ms(ts, &conn->ts_tap);
int tap_ms = timespec_diff_ms(ts, &conn->ts_tap);
switch (conn->state) {
case SOCK_SYN_SENT:
case TAP_SYN_RCVD:
if (ack_tap_ms > SYN_TIMEOUT)
tcp_rst(c, conn);
break;
case ESTABLISHED_SOCK_FIN:
if (ack_tap_ms > FIN_TIMEOUT) {
tcp_rst(c, conn);
break;
}
/* Falls through */
case ESTABLISHED:
if (tap_ms > ACT_TIMEOUT && sock_ms > ACT_TIMEOUT) {
tcp_rst(c, conn);
break;
}
if (conn->seq_to_tap == conn->seq_ack_from_tap &&
conn->seq_from_tap == conn->seq_ack_to_tap) {
conn->ts_sock = *ts;
break;
}
if (sock_ms > ACK_INTERVAL) {
if (conn->seq_from_tap > conn->seq_ack_to_tap)
tcp_send_to_tap(c, conn, ACK, NULL, 0);
}
if (ack_tap_ms > ACK_TIMEOUT) {
if (conn->seq_ack_from_tap < conn->seq_to_tap) {
if (ack_tap_ms > 10 * ACK_TIMEOUT) {
tcp_rst(c, conn);
break;
}
conn->seq_to_tap = conn->seq_ack_from_tap;
tcp_data_from_sock(c, conn, ts);
}
}
if (conn->seq_from_tap == conn->seq_ack_to_tap)
conn->ts_sock = *ts;
break;
case CLOSE_WAIT:
case FIN_WAIT_1:
if (sock_ms > FIN_TIMEOUT)
tcp_rst(c, conn);
break;
case FIN_WAIT_1_SOCK_FIN:
if (ack_tap_ms > FIN_TIMEOUT)
tcp_rst(c, conn);
break;
case LAST_ACK:
if (sock_ms > LAST_ACK_TIMEOUT)
tcp_rst(c, conn);
break;
case TAP_SYN_SENT:
case SPLICE_ACCEPTED:
case SPLICE_CONNECT:
case SPLICE_ESTABLISHED:
case CLOSED:
break;
}
}
/**
* tcp_timer() - Scan activity bitmap for sockets waiting for timed events
* @c: Execution context
* @ts: Timestamp from caller
*/
void tcp_timer(struct ctx *c, struct timespec *ts)
{
long *word = (long *)tcp_act, tmp;
unsigned int i;
int n;
for (i = 0; i < sizeof(tcp_act) / sizeof(long); i++, word++) {
tmp = *word;
while ((n = ffsl(tmp))) {
int index = i * sizeof(long) * 8 + n - 1;
tmp &= ~(1UL << (n - 1));
tcp_timer_one(c, &tt[index], ts);
}
}
}
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