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tcp: extract buffer management from tcp_send_flag()

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This commit isolates the internal data structure management used for storing
data (e.g., tcp4_l2_flags_iov[], tcp6_l2_flags_iov[], tcp4_flags_ip[],
tcp4_flags[], ...) from the tcp_send_flag() function. The extracted
functionality is relocated to a new function named tcp_fill_flag_header().

tcp_fill_flag_header() is now a generic function that accepts parameters such
as struct tcphdr and a data pointer. tcp_send_flag() utilizes this parameter to
pass memory pointers from tcp4_l2_flags_iov[] and tcp6_l2_flags_iov[].

This separation sets the stage for utilizing tcp_prepare_flags() to
set the memory provided by the guest via vhost-user in future developments.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Laurent Vivier 2024-06-13 14:36:48 +02:00 committed by Stefano Brivio
parent d949667436
commit ec26fa013a
1 changed files with 54 additions and 24 deletions
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78
tcp.c
View file

@ -1567,24 +1567,25 @@ static void tcp_update_seqack_from_tap(const struct ctx *c,
} }
/** /**
* tcp_send_flag() - Send segment with flags to tap (no payload) * tcp_prepare_flags() - Prepare header for flags-only segment (no payload)
* @c: Execution context * @c: Execution context
* @conn: Connection pointer * @conn: Connection pointer
* @flags: TCP flags: if not set, send segment only if ACK is due * @flags: TCP flags: if not set, send segment only if ACK is due
* @th: TCP header to update
* @data: buffer to store TCP option
* @optlen: size of the TCP option buffer (output parameter)
* *
* Return: negative error code on connection reset, 0 otherwise * Return: < 0 error code on connection reset,
* 0 if there is no flag to send
* 1 otherwise
*/ */
static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) static int tcp_prepare_flags(struct ctx *c, struct tcp_tap_conn *conn,
int flags, struct tcphdr *th, char *data,
size_t *optlen)
{ {
struct tcp_flags_t *payload;
struct tcp_info tinfo = { 0 }; struct tcp_info tinfo = { 0 };
socklen_t sl = sizeof(tinfo); socklen_t sl = sizeof(tinfo);
int s = conn->sock; int s = conn->sock;
size_t optlen = 0;
struct tcphdr *th;
struct iovec *iov;
size_t l4len;
char *data;
if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap) && if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap) &&
!flags && conn->wnd_to_tap) !flags && conn->wnd_to_tap)
@ -1606,20 +1607,12 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags)
if (!tcp_update_seqack_wnd(c, conn, flags, &tinfo) && !flags) if (!tcp_update_seqack_wnd(c, conn, flags, &tinfo) && !flags)
return 0; return 0;
if (CONN_V4(conn)) *optlen = 0;
iov = tcp4_l2_flags_iov[tcp4_flags_used++];
else
iov = tcp6_l2_flags_iov[tcp6_flags_used++];
payload = iov[TCP_IOV_PAYLOAD].iov_base;
th = &payload->th;
data = payload->opts;
if (flags & SYN) { if (flags & SYN) {
int mss; int mss;
/* Options: MSS, NOP and window scale (8 bytes) */ /* Options: MSS, NOP and window scale (8 bytes) */
optlen = OPT_MSS_LEN + 1 + OPT_WS_LEN; *optlen = OPT_MSS_LEN + 1 + OPT_WS_LEN;
*data++ = OPT_MSS; *data++ = OPT_MSS;
*data++ = OPT_MSS_LEN; *data++ = OPT_MSS_LEN;
@ -1653,17 +1646,13 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags)
flags |= ACK; flags |= ACK;
} }
th->doff = (sizeof(*th) + optlen) / 4; th->doff = (sizeof(*th) + *optlen) / 4;
th->ack = !!(flags & ACK); th->ack = !!(flags & ACK);
th->rst = !!(flags & RST); th->rst = !!(flags & RST);
th->syn = !!(flags & SYN); th->syn = !!(flags & SYN);
th->fin = !!(flags & FIN); th->fin = !!(flags & FIN);
l4len = tcp_l2_buf_fill_headers(c, conn, iov, optlen, NULL,
conn->seq_to_tap);
iov[TCP_IOV_PAYLOAD].iov_len = l4len;
if (th->ack) { if (th->ack) {
if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap)) if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap))
conn_flag(c, conn, ~ACK_TO_TAP_DUE); conn_flag(c, conn, ~ACK_TO_TAP_DUE);
@ -1678,6 +1667,47 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags)
if (th->fin || th->syn) if (th->fin || th->syn)
conn->seq_to_tap++; conn->seq_to_tap++;
return 1;
}
/**
* tcp_send_flag() - Send segment with flags to tap (no payload)
* @c: Execution context
* @conn: Connection pointer
* @flags: TCP flags: if not set, send segment only if ACK is due
*
* Return: negative error code on connection reset, 0 otherwise
*/
static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags)
{
struct tcp_flags_t *payload;
struct iovec *iov;
size_t optlen;
size_t l4len;
uint32_t seq;
int ret;
if (CONN_V4(conn))
iov = tcp4_l2_flags_iov[tcp4_flags_used++];
else
iov = tcp6_l2_flags_iov[tcp6_flags_used++];
payload = iov[TCP_IOV_PAYLOAD].iov_base;
seq = conn->seq_to_tap;
ret = tcp_prepare_flags(c, conn, flags, &payload->th,
payload->opts, &optlen);
if (ret <= 0) {
if (CONN_V4(conn))
tcp4_flags_used--;
else
tcp6_flags_used--;
return ret;
}
l4len = tcp_l2_buf_fill_headers(c, conn, iov, optlen, NULL, seq);
iov[TCP_IOV_PAYLOAD].iov_len = l4len;
if (flags & DUP_ACK) { if (flags & DUP_ACK) {
struct iovec *dup_iov; struct iovec *dup_iov;
int i; int i;