tcp: improve mss computation
Type: fix
Use different mss for v4 and v6 packets.
Change-Id: Ifcd322c1fd74f749a42bae671dd6cfed8c32b150
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index bfab1d6..cd7b9e8 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -638,6 +638,47 @@
}
/**
+ * Initialize max segment size we're able to process.
+ *
+ * The value is constrained by the output interface's MTU and by the size
+ * of the IP and TCP headers (see RFC6691). It is also what we advertise
+ * to our peer.
+ */
+static void
+tcp_init_rcv_mss (tcp_connection_t * tc)
+{
+ u8 ip_hdr_len;
+
+ ip_hdr_len = tc->c_is_ip4 ? sizeof (ip4_header_t) : sizeof (ip6_header_t);
+ tc->mss = tcp_cfg.default_mtu - sizeof (tcp_header_t) - ip_hdr_len;
+}
+
+static void
+tcp_init_mss (tcp_connection_t * tc)
+{
+ u16 default_min_mss = 536;
+
+ tcp_init_rcv_mss (tc);
+
+ /* TODO consider PMTU discovery */
+ tc->snd_mss = clib_min (tc->rcv_opts.mss, tc->mss);
+
+ if (tc->snd_mss < 45)
+ {
+ /* Assume that at least the min default mss works */
+ tc->snd_mss = default_min_mss;
+ tc->rcv_opts.mss = default_min_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->rcv_opts))
+ tc->snd_mss -= TCP_OPTION_LEN_TIMESTAMP;
+}
+
+/**
* Initialize connection send variables.
*/
void
@@ -651,6 +692,7 @@
*/
tcp_set_time_now (tcp_get_worker (vlib_get_thread_index ()));
+ tcp_init_rcv_mss (tc);
tc->iss = tcp_generate_random_iss (tc);
tc->snd_una = tc->iss;
tc->snd_nxt = tc->iss + 1;
@@ -1541,7 +1583,7 @@
tcp_cfg.max_rx_fifo = 32 << 20;
tcp_cfg.min_rx_fifo = 4 << 10;
- tcp_cfg.default_mtu = 1460;
+ tcp_cfg.default_mtu = 1500;
tcp_cfg.initial_cwnd_multiplier = 0;
tcp_cfg.enable_tx_pacing = 1;
tcp_cfg.cc_algo = TCP_CC_NEWRENO;