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Pull up following revision(s) (requested by msaitoh in ticket #424): 

sys/net/if_loop.c: revision 1.108
	sys/net/if_loop.c: revision 1.109

 Fix IP broadcast + checksum offload problem.

 When a machine sends a IP broadcast packet to an Ethernet interface that the
checksum offload flags are set, the packet goes through ether_output() ->
looutput() and the offload flags is cleared without calculating the checksum.

And then, ip_input() calculate the packet's checksum because it's csum_flags is
zero. It regard as bad checksum and it's dropped because the packet's ifp
is s not lo0's. Fixes this bug by passing csum_flags as "calculated and good"
when IN_LOOPBACK_NEED_CHECKSUM() is false. Advised by ryo@.

 This problem was seen when "routed -s" was used and the machine's interface's
offload flags were set. bad checksum field of "netstat -s" was increased every
30 seconds.

 Fix comment.
This commit is contained in:
martin 2019-11-14 15:34:35 +00:00
parent 18346d7d6a
commit 7108b34561
1 changed files with 14 additions and 4 deletions
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18
sys/net/if_loop.c
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@ -1,4 +1,4 @@
/* $NetBSD: if_loop.c,v 1.107 2019/04/26 08:38:25 pgoyette Exp $ */
/* $NetBSD: if_loop.c,v 1.107.2.1 2019/11/14 15:34:35 martin Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@ -65,7 +65,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: if_loop.c,v 1.107 2019/04/26 08:38:25 pgoyette Exp $");
__KERNEL_RCSID(0, "$NetBSD: if_loop.c,v 1.107.2.1 2019/11/14 15:34:35 martin Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@ -321,8 +321,13 @@ looutput(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *dst,
KASSERT((csum_flags & ~(M_CSUM_IPv4|M_CSUM_UDPv4)) == 0);
if (csum_flags != 0 && IN_LOOPBACK_NEED_CHECKSUM(csum_flags)) {
in_undefer_cksum(m, 0, csum_flags);
m->m_pkthdr.csum_flags = 0;
} else {
/*
* Do nothing. Pass M_CSUM_IPv4 and M_CSUM_UDPv4 as
* they are to tell those are calculated and good.
*/
}
m->m_pkthdr.csum_flags = 0;
pktq = ip_pktq;
break;
#endif
@ -333,8 +338,13 @@ looutput(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *dst,
if (csum_flags != 0 &&
IN6_LOOPBACK_NEED_CHECKSUM(csum_flags)) {
in6_undefer_cksum(m, 0, csum_flags);
m->m_pkthdr.csum_flags = 0;
} else {
/*
* Do nothing. Pass M_CSUM_UDPv6 as
* they are to tell those are calculated and good.
*/
}
m->m_pkthdr.csum_flags = 0;
m->m_flags |= M_LOOP;
pktq = ip6_pktq;
break;