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passt/tcp_conn.h
David Gibson 6ccab72d9b tcp: Improve handling of fallback if socket pool is empty on new splice 
When creating a new spliced connection, we need to get a socket in the
other ns from the originating one.  To avoid excessive ns switches we
usually get these from a pool refilled on a timer.  However, if the pool
runs out we need a fallback.  Currently that's done by passing -1 as the
socket to tcp_splice_connnect() and running it in the target ns.

This means that tcp_splice_connect() itself needs to have different cases
depending on whether it's given an existing socket or not, which is
a separate concern from what it's mostly doing.  We change it to require
a suitable open socket to be passed in, and ensuring in the caller that we
have one.

This requires adding the fallback paths to the caller, tcp_splice_new().
We use slightly different approaches for a socket in the init ns versus the
guest ns.

This also means that we no longer need to run tcp_splice_connect() itself
in the guest ns, which allows us to remove a bunch of boilerplate code.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2023-02-14 17:25:14 +01:00

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/* SPDX-License-Identifier: AGPL-3.0-or-later
* Copyright Red Hat
* Author: Stefano Brivio <sbrivio@redhat.com>
* Author: David Gibson <david@gibson.dropbear.id.au>
*
* TCP connection tracking data structures, used by tcp.c and
* tcp_splice.c. Shouldn't be included in non-TCP code.
*/
#ifndef TCP_CONN_H
#define TCP_CONN_H
/**
* struct tcp_conn_common - Common fields for spliced and non-spliced
* @spliced: Is this a spliced connection?
* @in_epoll: Is the connection in the epoll set?
*/
struct tcp_conn_common {
bool spliced :1;
bool in_epoll :1;
};
extern const char *tcp_common_flag_str[];
/**
* struct tcp_tap_conn - Descriptor for a TCP connection (not spliced)
* @c: Fields common with tcp_splice_conn
* @next_index: Connection index of next item in hash chain, -1 for none
* @tap_mss: MSS advertised by tap/guest, rounded to 2 ^ TCP_MSS_BITS
* @sock: Socket descriptor number
* @events: Connection events, implying connection states
* @timer: timerfd descriptor for timeout events
* @flags: Connection flags representing internal attributes
* @retrans: Number of retransmissions occurred due to ACK_TIMEOUT
* @ws_from_tap: Window scaling factor advertised from tap/guest
* @ws_to_tap: Window scaling factor advertised to tap/guest
* @sndbuf: Sending buffer in kernel, rounded to 2 ^ SNDBUF_BITS
* @seq_dup_ack_approx: Last duplicate ACK number sent to tap
* @addr: Remote address (IPv4 or IPv6)
* @tap_port: Guest-facing tap port
* @sock_port: Remote, socket-facing port
* @wnd_from_tap: Last window size from tap, unscaled (as received)
* @wnd_to_tap: Sending window advertised to tap, unscaled (as sent)
* @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
*/
struct tcp_tap_conn {
/* Must be first element to match tcp_splice_conn */
struct tcp_conn_common c;
int next_index :TCP_CONN_INDEX_BITS + 2;
#define TCP_RETRANS_BITS 3
unsigned int retrans :TCP_RETRANS_BITS;
#define TCP_MAX_RETRANS ((1U << TCP_RETRANS_BITS) - 1)
#define TCP_WS_BITS 4 /* RFC 7323 */
#define TCP_WS_MAX 14
unsigned int ws_from_tap :TCP_WS_BITS;
unsigned int ws_to_tap :TCP_WS_BITS;
int sock :SOCKET_REF_BITS;
uint8_t events;
#define CLOSED 0
#define SOCK_ACCEPTED BIT(0) /* implies SYN sent to tap */
#define TAP_SYN_RCVD BIT(1) /* implies socket connecting */
#define TAP_SYN_ACK_SENT BIT( 3) /* implies socket connected */
#define ESTABLISHED BIT(2)
#define SOCK_FIN_RCVD BIT( 3)
#define SOCK_FIN_SENT BIT( 4)
#define TAP_FIN_RCVD BIT( 5)
#define TAP_FIN_SENT BIT( 6)
#define TAP_FIN_ACKED BIT( 7)
#define CONN_STATE_BITS /* Setting these clears other flags */ \
(SOCK_ACCEPTED | TAP_SYN_RCVD | ESTABLISHED)
int timer :SOCKET_REF_BITS;
uint8_t flags;
#define STALLED BIT(0)
#define LOCAL BIT(1)
#define WND_CLAMPED BIT(2)
#define ACTIVE_CLOSE BIT(3)
#define ACK_TO_TAP_DUE BIT(4)
#define ACK_FROM_TAP_DUE BIT(5)
#define TCP_MSS_BITS 14
unsigned int tap_mss :TCP_MSS_BITS;
#define MSS_SET(conn, mss) (conn->tap_mss = (mss >> (16 - TCP_MSS_BITS)))
#define MSS_GET(conn) (conn->tap_mss << (16 - TCP_MSS_BITS))
#define SNDBUF_BITS 24
unsigned int sndbuf :SNDBUF_BITS;
#define SNDBUF_SET(conn, bytes) (conn->sndbuf = ((bytes) >> (32 - SNDBUF_BITS)))
#define SNDBUF_GET(conn) (conn->sndbuf << (32 - SNDBUF_BITS))
uint8_t seq_dup_ack_approx;
union inany_addr addr;
in_port_t tap_port;
in_port_t sock_port;
uint16_t wnd_from_tap;
uint16_t wnd_to_tap;
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;
};
/**
* struct tcp_splice_conn - Descriptor for a spliced TCP connection
* @c: Fields common with tcp_tap_conn
* @a: File descriptor number of socket for accepted connection
* @pipe_a_b: Pipe ends for splice() from @a to @b
* @b: File descriptor number of peer connected socket
* @pipe_b_a: Pipe ends for splice() from @b to @a
* @events: Events observed/actions performed on connection
* @flags: Connection flags (attributes, not events)
* @a_read: Bytes read from @a (not fully written to @b in one shot)
* @a_written: Bytes written to @a (not fully written from one @b read)
* @b_read: Bytes read from @b (not fully written to @a in one shot)
* @b_written: Bytes written to @b (not fully written from one @a read)
*/
struct tcp_splice_conn {
/* Must be first element to match tcp_tap_conn */
struct tcp_conn_common c;
int a;
int pipe_a_b[2];
int b;
int pipe_b_a[2];
uint8_t events;
#define SPLICE_CLOSED 0
#define SPLICE_CONNECT BIT(0)
#define SPLICE_ESTABLISHED BIT(1)
#define A_OUT_WAIT BIT(2)
#define B_OUT_WAIT BIT(3)
#define A_FIN_RCVD BIT(4)
#define B_FIN_RCVD BIT(5)
#define A_FIN_SENT BIT(6)
#define B_FIN_SENT BIT(7)
uint8_t flags;
#define SPLICE_V6 BIT(0)
#define RCVLOWAT_SET_A BIT(1)
#define RCVLOWAT_SET_B BIT(2)
#define RCVLOWAT_ACT_A BIT(3)
#define RCVLOWAT_ACT_B BIT(4)
#define CLOSING BIT(5)
uint32_t a_read;
uint32_t a_written;
uint32_t b_read;
uint32_t b_written;
};
/**
* union tcp_conn - Descriptor for a TCP connection (spliced or non-spliced)
* @c: Fields common between all variants
* @tap: Fields specific to non-spliced connections
* @splice: Fields specific to spliced connections
*/
union tcp_conn {
struct tcp_conn_common c;
struct tcp_tap_conn tap;
struct tcp_splice_conn splice;
};
/* TCP connections */
extern union tcp_conn tc[];
/* Socket pools */
#define TCP_SOCK_POOL_SIZE 32
extern int init_sock_pool4 [TCP_SOCK_POOL_SIZE];
extern int init_sock_pool6 [TCP_SOCK_POOL_SIZE];
void tcp_splice_conn_update(struct ctx *c, struct tcp_splice_conn *new);
void tcp_table_compact(struct ctx *c, union tcp_conn *hole);
void tcp_splice_destroy(struct ctx *c, union tcp_conn *conn_union);
void tcp_splice_timer(struct ctx *c, union tcp_conn *conn_union);
int tcp_conn_pool_sock(int pool[]);
int tcp_conn_new_sock(const struct ctx *c, sa_family_t af);
void tcp_sock_refill_pool(const struct ctx *c, int pool[], int af);
void tcp_splice_refill(const struct ctx *c);
#endif /* TCP_CONN_H */
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