From: bluhm <bluhm@openbsd.org>
Date: Fri, 7 Jul 2023 19:45:26 +0000 (+0000)
Subject: Keep mbuf header field ph_mss during loopback TCP with LRO/TSO.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=694d9bfd90e25287143f2b021ef2becec67cc4fd;p=openbsd

Keep mbuf header field ph_mss during loopback TCP with LRO/TSO.

When M_TCP_TSO is preserved, also keep ph_mss.  In lo(4) this logic
was missing.  This may be relevant only for weird pf configs that
forward from loopback.

OK mvs@ jan@
---

diff --git a/sys/net/if.c b/sys/net/if.c
index fd54cc813f3..27570bef2f2 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if.c,v 1.705 2023/07/07 08:05:02 bluhm Exp $	*/
+/*	$OpenBSD: if.c,v 1.706 2023/07/07 19:45:26 bluhm Exp $	*/
 /*	$NetBSD: if.c,v 1.35 1996/05/07 05:26:04 thorpej Exp $	*/
 
 /*
@@ -782,6 +782,7 @@ int
 if_input_local(struct ifnet *ifp, struct mbuf *m, sa_family_t af)
 {
 	int keepflags, keepcksum;
+	uint16_t keepmss;
 
 #if NBPFILTER > 0
 	/*
@@ -807,9 +808,11 @@ if_input_local(struct ifnet *ifp, struct mbuf *m, sa_family_t af)
 	keepcksum = m->m_pkthdr.csum_flags & (M_IPV4_CSUM_OUT |
 	    M_TCP_CSUM_OUT | M_UDP_CSUM_OUT | M_ICMP_CSUM_OUT |
 	    M_TCP_TSO);
+	keepmss = m->m_pkthdr.ph_mss;
 	m_resethdr(m);
 	m->m_flags |= M_LOOP | keepflags;
 	m->m_pkthdr.csum_flags = keepcksum;
+	m->m_pkthdr.ph_mss = keepmss;
 	m->m_pkthdr.ph_ifidx = ifp->if_index;
 	m->m_pkthdr.ph_rtableid = ifp->if_rdomain;