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PR kern/55779:

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restore non-desctructive guarantee of ip_mforward() mbuf
argument. This avoids generation invalid UDP checksums
on multicast packets in ip_output().

XXX the root cause of the misguided fix in 2008 should be
XXX investigated
This commit is contained in:
kardel 2020-11-12 13:13:45 +00:00
parent 2ca802e8e6
commit 4794d48d5e
1 changed files with 32 additions and 7 deletions
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39
sys/netinet/ip_mroute.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: ip_mroute.c,v 1.163 2018/09/14 05:09:51 maxv Exp $ */
/* $NetBSD: ip_mroute.c,v 1.164 2020/11/12 13:13:45 kardel Exp $ */
/*
* Copyright (c) 1992, 1993
@ -93,7 +93,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip_mroute.c,v 1.163 2018/09/14 05:09:51 maxv Exp $");
__KERNEL_RCSID(0, "$NetBSD: ip_mroute.c,v 1.164 2020/11/12 13:13:45 kardel Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@ -225,6 +225,8 @@ static int tbf_dq_sel(struct vif *, struct ip *);
static void tbf_send_packet(struct vif *, struct mbuf *);
static void tbf_update_tokens(struct vif *);
static int priority(struct vif *, struct ip *);
static int ip_mforward_real(struct mbuf *, struct ifnet *);
/*
* Bandwidth monitoring
@ -1267,6 +1269,34 @@ socket_send(struct socket *s, struct mbuf *mm, struct sockaddr_in *src)
int
ip_mforward(struct mbuf *m, struct ifnet *ifp)
{
int rc;
/*
* save csum_flags to uphold the
* "unscathed" guarantee.
* ip_output() relies on that and
* without it we send out
* multicast packets with an invalid
* checksum
*
* see PR kern/55779
*/
int csum_flags = m->m_pkthdr.csum_flags;
/*
* Temporarily clear any in-bound checksum flags for this packet.
*/
m->m_pkthdr.csum_flags = 0;
rc = ip_mforward_real(m, ifp);
m->m_pkthdr.csum_flags = csum_flags;
return rc;
}
static int
ip_mforward_real(struct mbuf *m, struct ifnet *ifp)
{
struct ip *ip = mtod(m, struct ip *);
struct mfc *rt;
@ -1304,11 +1334,6 @@ ip_mforward(struct mbuf *m, struct ifnet *ifp)
return EOPNOTSUPP;
}
/*
* Clear any in-bound checksum flags for this packet.
*/
m->m_pkthdr.csum_flags = 0;
/*
* Don't forward a packet with time-to-live of zero or one,
* or a packet destined to a local-only group.