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arp: Validate L2 sender hardware address matches ARP probe 

RFC 5227 section 1.1 states that for a DaD ARP probe the sender hardware
address must match the hardware address of the interface sending the
packet.

We can now verify this by checking the mbuf packet header.

This fixes an obsure issue where an old router was sending out bogus
ARP probes.
This commit is contained in:
roy 2022-11-14 09:32:21 +00:00
parent 17a43b3883
commit ef5ec13dab
1 changed files with 8 additions and 3 deletions
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11
sys/netinet/if_arp.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: if_arp.c,v 1.308 2022/09/03 01:35:03 thorpej Exp $ */
/* $NetBSD: if_arp.c,v 1.309 2022/11/14 09:32:21 roy Exp $ */
/*
* Copyright (c) 1998, 2000, 2008 The NetBSD Foundation, Inc.
@ -68,7 +68,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.308 2022/09/03 01:35:03 thorpej Exp $");
__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.309 2022/11/14 09:32:21 roy Exp $");
#ifdef _KERNEL_OPT
#include "opt_ddb.h"
@ -932,6 +932,8 @@ again:
/*
* DAD check, RFC 5227.
* ARP sender hardware address must match the interface
* address of the interface sending the packet.
* Collision on sender address is always a duplicate.
* Collision on target address is only a duplicate
* IF the sender address is the null host (ie a DAD probe)
@ -943,7 +945,10 @@ again:
(in_hosteq(isaddr, myaddr) ||
(in_nullhost(isaddr) && in_hosteq(itaddr, myaddr) &&
m->m_flags & M_BCAST &&
ia->ia4_flags & (IN_IFF_TENTATIVE | IN_IFF_DUPLICATED))))
ia->ia4_flags & (IN_IFF_TENTATIVE | IN_IFF_DUPLICATED))) &&
m->m_pkthdr.l2_shalen == ah->ar_hln && (
ah->ar_hln == 0 ||
memcmp(m->m_pkthdr.l2_sha, ar_sha(ah), ah->ar_hln) == 0))
{
struct sockaddr_dl sdl, *sdlp;