On Fri, May 31, 2024 at 04:23:36PM +0200, Laurent Vivier wrote: I think this needs a commit message. In particular expanding on what you mean by "buffer management" would be helpful.Signed-off-by: Laurent Vivier <lvivier(a)redhat.com> --- tcp.c | 87 ++++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 54 insertions(+), 33 deletions(-) diff --git a/tcp.c b/tcp.c index 6f221995f3bc..a6f43010f58f 100644 --- a/tcp.c +++ b/tcp.c @@ -1518,24 +1518,25 @@ static void tcp_update_seqack_from_tap(const struct ctx *c, } /** - * tcp_send_flag() - Send segment with flags to tap (no payload) + * tcp_fill_flag_header() - Prepare header for flags-only segment (no payload) * @c: Execution context * @conn: Connection pointer * @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 * - * 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_fill_flag_header(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 }; socklen_t sl = sizeof(tinfo); 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) && !flags && conn->wnd_to_tap) @@ -1557,20 +1558,11 @@ 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) return 0; - 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; - th = &payload->th; - data = payload->opts; - if (flags & SYN) { int mss; /* 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_LEN; @@ -1604,26 +1596,13 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) flags |= ACK; } - th->doff = (sizeof(*th) + optlen) / 4; + th->doff = (sizeof(*th) + *optlen) / 4; th->ack = !!(flags & ACK); th->rst = !!(flags & RST); th->syn = !!(flags & SYN); th->fin = !!(flags & FIN); - if (CONN_V4(conn)) { - l4len = tcp_fill_headers4(c, conn, iov[TCP_IOV_TAP].iov_base, - iov[TCP_IOV_IP].iov_base, - iov[TCP_IOV_PAYLOAD].iov_base, optlen, - NULL, conn->seq_to_tap); - } else { - l4len = tcp_fill_headers6(c, conn, iov[TCP_IOV_TAP].iov_base, - iov[TCP_IOV_IP].iov_base, - iov[TCP_IOV_PAYLOAD].iov_base, optlen, - conn->seq_to_tap); - } - iov[TCP_IOV_PAYLOAD].iov_len = l4len; - if (th->ack) { if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap)) conn_flag(c, conn, ~ACK_TO_TAP_DUE); @@ -1638,6 +1617,48 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) if (th->fin || th->syn) conn->seq_to_tap++; + return 1; +} + +static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) +{ + struct tcp_flags_t *payload; + size_t optlen = 0; + struct iovec *iov; + size_t l4len; + int ret; + + if (CONN_V4(conn)) { + iov = tcp4_l2_flags_iov[tcp4_flags_used++];Hrm.. it does occur to me that if you avoided the previous patch, keeping a single dispatcher for filling in the IP headers, then setting the iov pointer would become the only v4/v6 dependent part of this function, helping us down the road of unifying that more. Obviously there would be a separate CONN_v4() check hidden inside fill_headers(), but as I've said I'm already aiming to replace those with more specific tests.+ payload = iov[TCP_IOV_PAYLOAD].iov_base; + + ret = tcp_fill_flag_header(c, conn, flags, &payload->th, + payload->opts, &optlen); + if (ret <= 0) + return ret; + + l4len = tcp_fill_headers4(c, conn, iov[TCP_IOV_TAP].iov_base, + iov[TCP_IOV_IP].iov_base, + iov[TCP_IOV_PAYLOAD].iov_base, optlen, + NULL, conn->seq_to_tap); + } else { + iov = tcp6_l2_flags_iov[tcp6_flags_used++]; + + payload = iov[TCP_IOV_PAYLOAD].iov_base; + + ret = tcp_fill_flag_header(c, conn, flags, &payload->th, + payload->opts, &optlen); + if (ret <= 0) + return ret; + + l4len = tcp_fill_headers6(c, conn, iov[TCP_IOV_TAP].iov_base, + iov[TCP_IOV_IP].iov_base, + iov[TCP_IOV_PAYLOAD].iov_base, optlen, + conn->seq_to_tap); + } + iov[TCP_IOV_PAYLOAD].iov_len = l4len; + if (flags & DUP_ACK) { struct iovec *dup_iov; int i;-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson