tcp_send_flag() can fail in two different ways: - tcp_prepare_flags() returns -ECONNRESET when getsockopt(TCP_INFO) fails: the socket is broken and the connection must be reset. - tcp_vu_send_flag() returns -EAGAIN when vu_collect() finds no available vhost-user buffers: this is a transient condition equivalent to a dropped packet on the wire. Have tcp_vu_send_flag() return -EAGAIN instead of a bare -1 for the buffer-unavailable case. Absorb -EAGAIN in the tcp_send_flag() dispatcher so that callers only see fatal errors. Check the return value at each call site and handle fatal errors: - in tcp_data_from_tap(), return -1 so the caller resets - in tcp_tap_handler(), goto reset - in tcp_timer_handler()/tcp_sock_handler()/tcp_conn_from_sock_finish(), call tcp_rst() and return - in tcp_tap_conn_from_sock(), set CLOSING flag, call FLOW_ACTIVATE() to avoid leaving the flow in TYPED state, and return - in tcp_connect_finish(), call tcp_rst() and return - in tcp_keepalive(), call tcp_rst() and continue the loop - in tcp_flow_migrate_target_ext(), goto fail The call in tcp_rst_do() is left unchecked: we are already resetting, and tcp_sock_rst() still needs to run regardless. Link: https://bugs.passt.top/show_bug.cgi?id=194 Signed-off-by: Anshu Kumari --- v2: - updated commit message. - update tcp_vu_send_flag() to return -EAGAIN instead of -1 for buffer-unavailable case. - in tcp_tap_conn_from_sock(), added FLOW_ACTIVATE call. - inside tcp_send_flag(), updated the return statement. function will return 0 incase of -EAGAIN error. --- tcp.c | 74 +++++++++++++++++++++++++++++++++++++++++--------------- tcp_vu.c | 6 +++-- 2 files changed, 59 insertions(+), 21 deletions(-) diff --git a/tcp.c b/tcp.c index 8ea9be8..28139d8 100644 --- a/tcp.c +++ b/tcp.c @@ -1378,15 +1378,19 @@ int tcp_prepare_flags(const struct ctx *c, struct tcp_tap_conn *conn, * @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 + * Return: negative error code on fatal connection failure, 0 otherwise */ static int tcp_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) { + int ret; + if (c->mode == MODE_VU) - return tcp_vu_send_flag(c, conn, flags); + ret = tcp_vu_send_flag(c, conn, flags); + else + ret = tcp_buf_send_flag(c, conn, flags); - return tcp_buf_send_flag(c, conn, flags); + return ret == -EAGAIN ? 0 : ret; } /** @@ -1917,7 +1921,9 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn, "keep-alive sequence: %u, previous: %u", seq, conn->seq_from_tap); - tcp_send_flag(c, conn, ACK); + if (tcp_send_flag(c, conn, ACK)) + return -1; + tcp_timer_ctl(c, conn); if (setsockopt(conn->sock, SOL_SOCKET, SO_KEEPALIVE, @@ -2043,14 +2049,16 @@ eintr: * Then swiftly looked away and left. */ conn->seq_from_tap = seq_from_tap; - tcp_send_flag(c, conn, ACK); + if (tcp_send_flag(c, conn, ACK)) + return -1; } if (errno == EINTR) goto eintr; if (errno == EAGAIN || errno == EWOULDBLOCK) { - tcp_send_flag(c, conn, ACK | DUP_ACK); + if (tcp_send_flag(c, conn, ACK | DUP_ACK)) + return -1; return p->count - idx; } @@ -2070,7 +2078,8 @@ out: */ if (conn->seq_dup_ack_approx != (conn->seq_from_tap & 0xff)) { conn->seq_dup_ack_approx = conn->seq_from_tap & 0xff; - tcp_send_flag(c, conn, ACK | DUP_ACK); + if (tcp_send_flag(c, conn, ACK | DUP_ACK)) + return -1; } return p->count - idx; } @@ -2084,7 +2093,8 @@ out: conn_event(c, conn, TAP_FIN_RCVD); } else { - tcp_send_flag(c, conn, ACK_IF_NEEDED); + if (tcp_send_flag(c, conn, ACK_IF_NEEDED)) + return -1; } return p->count - idx; @@ -2122,7 +2132,10 @@ static void tcp_conn_from_sock_finish(const struct ctx *c, return; } - tcp_send_flag(c, conn, ACK); + if (tcp_send_flag(c, conn, ACK)) { + tcp_rst(c, conn); + return; + } /* The client might have sent data already, which we didn't * dequeue waiting for SYN,ACK from tap -- check now. @@ -2308,7 +2321,9 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, goto reset; } - tcp_send_flag(c, conn, ACK); + if (tcp_send_flag(c, conn, ACK)) + goto reset; + conn_event(c, conn, SOCK_FIN_SENT); return 1; @@ -2388,7 +2403,9 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, } conn_event(c, conn, SOCK_FIN_SENT); - tcp_send_flag(c, conn, ACK); + if (tcp_send_flag(c, conn, ACK)) + goto reset; + ack_due = 0; /* If we received a FIN, but the socket is in TCP_ESTABLISHED @@ -2436,8 +2453,10 @@ static void tcp_connect_finish(const struct ctx *c, struct tcp_tap_conn *conn) return; } - if (tcp_send_flag(c, conn, SYN | ACK)) + if (tcp_send_flag(c, conn, SYN | ACK)) { + tcp_rst(c, conn); return; + } conn_event(c, conn, TAP_SYN_ACK_SENT); conn_flag(c, conn, ACK_FROM_TAP_DUE); @@ -2478,7 +2497,12 @@ static void tcp_tap_conn_from_sock(const struct ctx *c, union flow *flow, conn->wnd_from_tap = WINDOW_DEFAULT; - tcp_send_flag(c, conn, SYN); + if (tcp_send_flag(c, conn, SYN)) { + conn_flag(c, conn, CLOSING); + FLOW_ACTIVATE(conn); + return; + } + conn_flag(c, conn, ACK_FROM_TAP_DUE); tcp_get_sndbuf(conn); @@ -2585,7 +2609,10 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref) return; if (conn->flags & ACK_TO_TAP_DUE) { - tcp_send_flag(c, conn, ACK_IF_NEEDED); + if (tcp_send_flag(c, conn, ACK_IF_NEEDED)) { + tcp_rst(c, conn); + return; + } tcp_timer_ctl(c, conn); } else if (conn->flags & ACK_FROM_TAP_DUE) { if (!(conn->events & ESTABLISHED)) { @@ -2598,7 +2625,10 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref) tcp_rst(c, conn); } else { flow_trace(conn, "SYN timeout, retry"); - tcp_send_flag(c, conn, SYN); + if (tcp_send_flag(c, conn, SYN)) { + tcp_rst(c, conn); + return; + } conn->retries++; conn_flag(c, conn, SYN_RETRIED); tcp_timer_ctl(c, conn); @@ -2662,8 +2692,11 @@ void tcp_sock_handler(const struct ctx *c, union epoll_ref ref, tcp_data_from_sock(c, conn); if (events & EPOLLOUT) { - if (tcp_update_seqack_wnd(c, conn, false, NULL)) - tcp_send_flag(c, conn, ACK); + if (tcp_update_seqack_wnd(c, conn, false, NULL) && + tcp_send_flag(c, conn, ACK)) { + tcp_rst(c, conn); + return; + } } return; @@ -2903,7 +2936,8 @@ static void tcp_keepalive(struct ctx *c, const struct timespec *now) if (conn->tap_inactive) { flow_dbg(conn, "No tap activity for least %us, send keepalive", KEEPALIVE_INTERVAL); - tcp_send_flag(c, conn, KEEPALIVE); + if (tcp_send_flag(c, conn, KEEPALIVE)) + tcp_rst(c, conn); } /* Ready to check fot next interval */ @@ -3926,7 +3960,9 @@ int tcp_flow_migrate_target_ext(struct ctx *c, struct tcp_tap_conn *conn, int fd if (tcp_set_peek_offset(conn, peek_offset)) goto fail; - tcp_send_flag(c, conn, ACK); + if (tcp_send_flag(c, conn, ACK)) + goto fail; + tcp_data_from_sock(c, conn); if ((rc = tcp_epoll_ctl(conn))) { diff --git a/tcp_vu.c b/tcp_vu.c index dc0e17c..9d63a30 100644 --- a/tcp_vu.c +++ b/tcp_vu.c @@ -65,7 +65,9 @@ static size_t tcp_vu_hdrlen(bool v6) * @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 + * Return: -ECONNRESET on fatal connection error, + * -EAGAIN if vhost-user buffers are unavailable, + * 0 otherwise */ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) { @@ -91,7 +93,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) &flags_iov[0], 1, NULL, MAX(hdrlen + sizeof(*opts), ETH_ZLEN + VNET_HLEN), NULL); if (elem_cnt != 1) - return -1; + return -EAGAIN; assert(flags_elem[0].in_num == 1); assert(flags_elem[0].in_sg[0].iov_len >= -- 2.53.0