9e5df350d6
As a rule, we prefer constructing packets with matching C structures, rather than building them byte by byte. However, one case we still build byte by byte is the TCP options we include in SYN packets (in fact the only time we generate TCP options on the tap interface). Rework this to use a structure and initialisers which make it a bit clearer what's going on. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by; Stefano Brivio <sbrivio@redhat.com>
188 lines
5 KiB
C
188 lines
5 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later
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* Copyright (c) 2021 Red Hat GmbH
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* Author: Stefano Brivio <sbrivio@redhat.com>
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*/
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#ifndef TCP_INTERNAL_H
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#define TCP_INTERNAL_H
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#define MAX_WS 8
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#define MAX_WINDOW (1 << (16 + (MAX_WS)))
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#define MSS4 ROUND_DOWN(IP_MAX_MTU - \
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sizeof(struct tcphdr) - \
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sizeof(struct iphdr), \
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sizeof(uint32_t))
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#define MSS6 ROUND_DOWN(IP_MAX_MTU - \
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sizeof(struct tcphdr) - \
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sizeof(struct ipv6hdr), \
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sizeof(uint32_t))
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#define SEQ_LE(a, b) ((b) - (a) < MAX_WINDOW)
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#define SEQ_LT(a, b) ((b) - (a) - 1 < MAX_WINDOW)
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#define SEQ_GE(a, b) ((a) - (b) < MAX_WINDOW)
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#define SEQ_GT(a, b) ((a) - (b) - 1 < MAX_WINDOW)
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#define FIN (1 << 0)
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#define SYN (1 << 1)
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#define RST (1 << 2)
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#define ACK (1 << 4)
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/* Flags for internal usage */
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#define DUP_ACK (1 << 5)
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#define OPT_EOL 0
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#define OPT_NOP 1
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#define OPT_MSS 2
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#define OPT_WS 3
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#define OPT_SACKP 4
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#define OPT_SACK 5
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#define OPT_TS 8
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#define TAPSIDE(conn_) ((conn_)->f.pif[1] == PIF_TAP)
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#define TAPFLOW(conn_) (&((conn_)->f.side[TAPSIDE(conn_)]))
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#define TAP_SIDX(conn_) (FLOW_SIDX((conn_), TAPSIDE(conn_)))
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#define CONN_V4(conn) (!!inany_v4(&TAPFLOW(conn)->oaddr))
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#define CONN_V6(conn) (!CONN_V4(conn))
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/*
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* enum tcp_iov_parts - I/O vector parts for one TCP frame
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* @TCP_IOV_TAP tap backend specific header
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* @TCP_IOV_ETH Ethernet header
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* @TCP_IOV_IP IP (v4/v6) header
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* @TCP_IOV_PAYLOAD IP payload (TCP header + data)
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* @TCP_NUM_IOVS the number of entries in the iovec array
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*/
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enum tcp_iov_parts {
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TCP_IOV_TAP = 0,
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TCP_IOV_ETH = 1,
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TCP_IOV_IP = 2,
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TCP_IOV_PAYLOAD = 3,
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TCP_NUM_IOVS
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};
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/**
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* struct tcp_payload_t - TCP header and data to send segments with payload
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* @th: TCP header
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* @data: TCP data
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*/
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struct tcp_payload_t {
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struct tcphdr th;
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uint8_t data[IP_MAX_MTU - sizeof(struct tcphdr)];
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#ifdef __AVX2__
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} __attribute__ ((packed, aligned(32))); /* For AVX2 checksum routines */
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#else
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} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
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#endif
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/** struct tcp_opt_nop - TCP NOP option
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* @kind: Option kind (OPT_NOP = 1)
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*/
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struct tcp_opt_nop {
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uint8_t kind;
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} __attribute__ ((packed));
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#define TCP_OPT_NOP ((struct tcp_opt_nop){ .kind = OPT_NOP, })
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/** struct tcp_opt_mss - TCP MSS option
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* @kind: Option kind (OPT_MSS == 2)
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* @len: Option length (4)
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* @mss: Maximum Segment Size
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*/
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struct tcp_opt_mss {
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uint8_t kind;
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uint8_t len;
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uint16_t mss;
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} __attribute__ ((packed));
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#define TCP_OPT_MSS(mss_) \
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((struct tcp_opt_mss) { \
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.kind = OPT_MSS, \
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.len = sizeof(struct tcp_opt_mss), \
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.mss = htons(mss_), \
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})
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/** struct tcp_opt_ws - TCP Window Scaling option
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* @kind: Option kind (OPT_WS == 3)
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* @len: Option length (3)
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* @shift: Window scaling shift
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*/
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struct tcp_opt_ws {
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uint8_t kind;
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uint8_t len;
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uint8_t shift;
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} __attribute__ ((packed));
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#define TCP_OPT_WS(shift_) \
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((struct tcp_opt_ws) { \
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.kind = OPT_WS, \
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.len = sizeof(struct tcp_opt_ws), \
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.shift = (shift_), \
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})
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/** struct tcp_syn_opts - TCP options we apply to SYN packets
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* @mss: Maximum Segment Size (MSS) option
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* @nop: NOP opt (for alignment)
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* @ws: Window Scaling (WS) option
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*/
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struct tcp_syn_opts {
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struct tcp_opt_mss mss;
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struct tcp_opt_nop nop;
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struct tcp_opt_ws ws;
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} __attribute__ ((packed));
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#define TCP_SYN_OPTS(mss_, ws_) \
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((struct tcp_syn_opts){ \
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.mss = TCP_OPT_MSS(mss_), \
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.nop = TCP_OPT_NOP, \
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.ws = TCP_OPT_WS(ws_), \
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})
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/**
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* struct tcp_flags_t - TCP header and data to send zero-length
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* segments (flags)
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* @th: TCP header
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* @opts TCP options
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*/
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struct tcp_flags_t {
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struct tcphdr th;
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struct tcp_syn_opts opts;
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#ifdef __AVX2__
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} __attribute__ ((packed, aligned(32)));
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#else
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} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
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#endif
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extern char tcp_buf_discard [MAX_WINDOW];
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void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
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unsigned long flag);
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#define conn_flag(c, conn, flag) \
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do { \
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flow_trace(conn, "flag at %s:%i", __func__, __LINE__); \
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conn_flag_do(c, conn, flag); \
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} while (0)
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void conn_event_do(const struct ctx *c, struct tcp_tap_conn *conn,
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unsigned long event);
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#define conn_event(c, conn, event) \
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do { \
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flow_trace(conn, "event at %s:%i", __func__, __LINE__); \
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conn_event_do(c, conn, event); \
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} while (0)
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void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn);
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#define tcp_rst(c, conn) \
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do { \
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flow_dbg((conn), "TCP reset at %s:%i", __func__, __LINE__); \
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tcp_rst_do(c, conn); \
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} while (0)
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size_t tcp_l2_buf_fill_headers(const struct tcp_tap_conn *conn,
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struct iovec *iov, size_t dlen,
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const uint16_t *check, uint32_t seq,
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bool no_tcp_csum);
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int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn,
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bool force_seq, struct tcp_info *tinfo);
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int tcp_prepare_flags(const struct ctx *c, struct tcp_tap_conn *conn,
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int flags, struct tcphdr *th, struct tcp_syn_opts *opts,
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size_t *optlen);
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#endif /* TCP_INTERNAL_H */
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