From c8343412ee0deaa8e9192cbc4846aae1e9f48a4d Mon Sep 17 00:00:00 2001 From: Florin Coras Date: Thu, 4 May 2017 14:25:50 -0700 Subject: Include TCP options in segment size computation Ensure that TCP data plus options does not exceed peer's advertised MSS. Change-Id: I0de824cb3619346f0394dd694942fc1cf33a82b7 Signed-off-by: Florin Coras --- src/vnet/tcp/tcp_output.c | 104 ++++++++++++++++++++++++++++++---------------- 1 file changed, 69 insertions(+), 35 deletions(-) (limited to 'src/vnet/tcp/tcp_output.c') diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c index 7ee930c6..2a1b1407 100644 --- a/src/vnet/tcp/tcp_output.c +++ b/src/vnet/tcp/tcp_output.c @@ -64,26 +64,6 @@ format_tcp_tx_trace (u8 * s, va_list * args) return s; } -void -tcp_set_snd_mss (tcp_connection_t * tc) -{ - u16 snd_mss; - - /* TODO find our iface MTU */ - snd_mss = dummy_mtu; - - /* TODO cache mss and consider PMTU discovery */ - snd_mss = clib_min (tc->opt.mss, snd_mss); - - tc->snd_mss = snd_mss; - - if (tc->snd_mss == 0) - { - clib_warning ("snd mss is 0"); - tc->snd_mss = dummy_mtu; - } -} - static u8 tcp_window_compute_scale (u32 available_space) { @@ -100,7 +80,7 @@ tcp_window_compute_scale (u32 available_space) always_inline u32 tcp_initial_wnd_unscaled (tcp_connection_t * tc) { - return TCP_IW_N_SEGMENTS * dummy_mtu; + return TCP_IW_N_SEGMENTS * tc->mss; } /** @@ -310,7 +290,7 @@ tcp_make_synack_options (tcp_connection_t * tc, tcp_options_t * opts) u8 len = 0; opts->flags |= TCP_OPTS_FLAG_MSS; - opts->mss = dummy_mtu; /*XXX discover that */ + opts->mss = tc->mss; len += TCP_OPTION_LEN_MSS; if (tcp_opts_wscale (&tc->opt)) @@ -389,6 +369,57 @@ tcp_make_options (tcp_connection_t * tc, tcp_options_t * opts, } } +/** + * Update max segment size we're able to process. + * + * The value is constrained by our interface's MTU and IP options. It is + * also what we advertise to our peer. + */ +void +tcp_update_rcv_mss (tcp_connection_t * tc) +{ + /* TODO find our iface MTU */ + tc->mss = dummy_mtu; +} + +/** + * Update snd_mss to reflect the effective segment size that we can send + * by taking into account all TCP options, including SACKs + */ +void +tcp_update_snd_mss (tcp_connection_t * tc) +{ + /* Compute options to be used for connection. These may be reused when + * sending data or to compute the effective mss (snd_mss) */ + tc->snd_opts_len = + tcp_make_options (tc, &tc->snd_opts, TCP_STATE_ESTABLISHED); + + /* XXX check if MTU has been updated */ + tc->snd_mss = clib_min (tc->mss, tc->opt.mss) - tc->snd_opts_len; +} + +void +tcp_init_mss (tcp_connection_t * tc) +{ + tcp_update_rcv_mss (tc); + + /* TODO cache mss and consider PMTU discovery */ + tc->snd_mss = clib_min (tc->opt.mss, tc->mss); + + if (tc->snd_mss == 0) + { + clib_warning ("snd mss is 0"); + tc->snd_mss = tc->mss; + } + + /* We should have enough space for 40 bytes of options */ + ASSERT (tc->snd_mss > 45); + + /* If we use timestamp option, account for it */ + if (tcp_opts_tstamp (&tc->opt)) + tc->snd_mss -= TCP_OPTION_LEN_TIMESTAMP; +} + #define tcp_get_free_buffer_index(tm, bidx) \ do { \ u32 *my_tx_buffers, n_free_buffers; \ @@ -886,20 +917,20 @@ tcp_make_state_flags (tcp_state_t next_state) */ static void tcp_push_hdr_i (tcp_connection_t * tc, vlib_buffer_t * b, - tcp_state_t next_state) + tcp_state_t next_state, u8 compute_opts) { u32 advertise_wnd, data_len; - u8 tcp_opts_len, tcp_hdr_opts_len, opts_write_len, flags; - tcp_options_t _snd_opts, *snd_opts = &_snd_opts; + u8 tcp_hdr_opts_len, opts_write_len, flags; tcp_header_t *th; data_len = b->current_length; vnet_buffer (b)->tcp.flags = 0; - /* Make and write options */ - memset (snd_opts, 0, sizeof (*snd_opts)); - tcp_opts_len = tcp_make_options (tc, snd_opts, next_state); - tcp_hdr_opts_len = tcp_opts_len + sizeof (tcp_header_t); + if (compute_opts) + tc->snd_opts_len = tcp_make_options (tc, &tc->snd_opts, tc->state); + + /* Write pre-computed options */ + tcp_hdr_opts_len = tc->snd_opts_len + sizeof (tcp_header_t); /* Get rcv window to advertise */ advertise_wnd = tcp_window_to_advertise (tc, next_state); @@ -910,9 +941,9 @@ tcp_push_hdr_i (tcp_connection_t * tc, vlib_buffer_t * b, tc->rcv_nxt, tcp_hdr_opts_len, flags, advertise_wnd); - opts_write_len = tcp_options_write ((u8 *) (th + 1), snd_opts); + opts_write_len = tcp_options_write ((u8 *) (th + 1), &tc->snd_opts); - ASSERT (opts_write_len == tcp_opts_len); + ASSERT (opts_write_len == tc->snd_opts_len); /* Tag the buffer with the connection index */ vnet_buffer (b)->tcp.connection_index = tc->c_c_index; @@ -993,6 +1024,8 @@ tcp_prepare_retransmit_segment (tcp_connection_t * tc, vlib_buffer_t * b, goto done; } + tc->snd_opts_len = tcp_make_options (tc, &tc->snd_opts, tc->state); + ASSERT (max_bytes <= tc->snd_mss); n_bytes = stream_session_peek_bytes (&tc->connection, @@ -1000,7 +1033,7 @@ tcp_prepare_retransmit_segment (tcp_connection_t * tc, vlib_buffer_t * b, max_bytes); ASSERT (n_bytes != 0); b->current_length = n_bytes; - tcp_push_hdr_i (tc, b, tc->state); + tcp_push_hdr_i (tc, b, tc->state, 0); tc->rtx_bytes += n_bytes; done: @@ -1097,7 +1130,7 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn) vlib_buffer_make_headroom (b, MAX_HDRS_LEN); - tcp_push_hdr_i (tc, b, tc->state); + tcp_push_hdr_i (tc, b, tc->state, 1); /* Account for the SYN */ tc->snd_nxt += 1; @@ -1168,6 +1201,7 @@ tcp_timer_persist_handler (u32 index) /* Try to force the first unsent segment */ tcp_get_free_buffer_index (tm, &bi); b = vlib_get_buffer (vm, bi); + tc->snd_opts_len = tcp_make_options (tc, &tc->snd_opts, tc->state); n_bytes = stream_session_peek_bytes (&tc->connection, vlib_buffer_get_current (b), tc->snd_una_max - tc->snd_una, @@ -1180,7 +1214,7 @@ tcp_timer_persist_handler (u32 index) } b->current_length = n_bytes; - tcp_push_hdr_i (tc, b, tc->state); + tcp_push_hdr_i (tc, b, tc->state, 0); tcp_enqueue_to_output (vm, b, bi, tc->c_is_ip4); /* Re-enable persist timer */ @@ -1507,7 +1541,7 @@ tcp_push_header (transport_connection_t * tconn, vlib_buffer_t * b) tcp_connection_t *tc; tc = (tcp_connection_t *) tconn; - tcp_push_hdr_i (tc, b, TCP_STATE_ESTABLISHED); + tcp_push_hdr_i (tc, b, TCP_STATE_ESTABLISHED, 0); return 0; } -- cgit 1.2.3-korg