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Comply with RFC 3927, by forcing ARP replies which contain a source

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address within the link-local IPv4 prefix 169.254.0.0/16, to be
broadcast at link layer.

Reviewed by:	fenner
MFC after:	2 weeks
This commit is contained in:
Bruce M Simpson 2007-02-02 20:31:44 +00:00
parent 8866f04eb1
commit d055815799
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=166436
1 changed files with 13 additions and 1 deletions
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14
sys/netinet/if_ether.c
View file

@ -885,11 +885,23 @@ in_arpinput(m)
}
}
if (itaddr.s_addr == myaddr.s_addr &&
IN_LINKLOCAL(ntohl(itaddr.s_addr))) {
/* RFC 3927 link-local IPv4; always reply by broadcast. */
#ifdef DEBUG_LINKLOCAL
printf("arp: sending reply for link-local addr %s\n",
inet_ntoa(itaddr));
#endif
m->m_flags |= M_BCAST;
m->m_flags &= ~M_MCAST;
} else {
/* default behaviour; never reply by broadcast. */
m->m_flags &= ~(M_BCAST|M_MCAST);
}
(void)memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
(void)memcpy(ar_spa(ah), &itaddr, ah->ar_pln);
ah->ar_op = htons(ARPOP_REPLY);
ah->ar_pro = htons(ETHERTYPE_IP); /* let's be sure! */
m->m_flags &= ~(M_BCAST|M_MCAST); /* never reply by broadcast */
m->m_len = sizeof(*ah) + (2 * ah->ar_pln) + (2 * ah->ar_hln);
m->m_pkthdr.len = m->m_len;
sa.sa_family = AF_ARP;