From: Ben Magistro <koncept1@gmail.com>
Date: Sat, 29 Jan 2022 17:32:25 +0000 (+0000)
Subject: Set a default MSS when establishing tcb if unset
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F46%2F35146%2F2;p=tldk.git

Set a default MSS when establishing tcb if unset

While the caller to tle_tcp_stream_establish, should provide a complete
connection info to include mss, if it is not provided it will trigger a
divide by zero in tle_tcp_stream_writev. RFCs have defined a default
value for IPv4 and IPv6, which is leveraged if left unspecified.

Signed-off-by: Ben Magistro <koncept1@gmail.com>
Change-Id: Ic29f4398b22a601eddf2a501e9cc185106457303
---

diff --git a/lib/libtle_l4p/tcp_rxtx.c b/lib/libtle_l4p/tcp_rxtx.c
index a702177..3d1c550 100644
--- a/lib/libtle_l4p/tcp_rxtx.c
+++ b/lib/libtle_l4p/tcp_rxtx.c
@@ -2277,7 +2277,17 @@ tcb_establish(struct tle_tcp_stream *s, const struct tle_tcp_conn_info *ci)
 	uint32_t mss, tms;
 
 	tms = tcp_get_tms(s->s.ctx->cycles_ms_shift);
-	mss = calc_smss(ci->so.mss, &s->tx.dst);
+
+	/* set a default MSS if it is unset (0) */
+	if ((ci->so.mss == 0) && (s->s.type == TLE_V4)) {
+		mss = calc_smss(TCP4_MIN_MSS, &s->tx.dst);
+	}
+	else if ((ci->so.mss == 0) && (s->s.type == TLE_V6)) {
+		mss = calc_smss(TCP6_MIN_MSS, &s->tx.dst);
+	}
+	else {
+		mss = calc_smss(ci->so.mss, &s->tx.dst);
+	}
 
 	s->tcb.so = ci->so;
 	fill_tcb_snd(&s->tcb, ci->ack, ci->seq, mss,