From: Florin Coras <fcoras@cisco.com>
Date: Fri, 5 Mar 2021 21:30:18 +0000 (-0800)
Subject: tcp: account for option alignment in initial snd_mss
X-Git-Tag: v21.10-rc0~400
X-Git-Url: https://gerrit.fd.io/r/gitweb?p=vpp.git;a=commitdiff_plain;h=7a588fc7819153fe32e7d12733da4ecd2e663437

tcp: account for option alignment in initial snd_mss

Type: fix

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I24225ada6623c5b5543341ecac0d6c1db43cc8a9
---

diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index 407ba9576a8..161b8ef25a2 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -657,9 +657,10 @@ tcp_init_mss (tcp_connection_t * tc)
   /* We should have enough space for 40 bytes of options */
   ASSERT (tc->snd_mss > 45);
 
-  /* If we use timestamp option, account for it */
+  /* If we use timestamp option, account for it and make sure
+   * the options are 4-byte aligned */
   if (tcp_opts_tstamp (&tc->rcv_opts))
-    tc->snd_mss -= TCP_OPTION_LEN_TIMESTAMP;
+    tc->snd_mss -= TCP_OPTION_LEN_TIMESTAMP + 2 /* alignment */;
 }
 
 /**