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Add support for IPv4 /31 prefixes, as described in RFC3021.

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To run a /31 network, participating hosts MUST drop support
for directed broadcasts, and treat the first and last addresses
on subnet as unicast. The broadcast address for the prefix
should be the link local broadcast address, INADDR_BROADCAST.
This commit is contained in:
Gleb Smirnoff 2011-10-15 18:41:25 +00:00
parent b365d954cc
commit 53883e0c24
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=226402
2 changed files with 11 additions and 4 deletions
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13
sys/netinet/in.c
View File

@ -897,8 +897,11 @@ in_ifinit(struct ifnet *ifp, struct in_ifaddr *ia, struct sockaddr_in *sin,
*/
ia->ia_ifa.ifa_metric = ifp->if_metric;
if (ifp->if_flags & IFF_BROADCAST) {
ia->ia_broadaddr.sin_addr.s_addr =
htonl(ia->ia_subnet | ~ia->ia_subnetmask);
if (ia->ia_subnetmask == IN_RFC3021_MASK)
ia->ia_broadaddr.sin_addr.s_addr = INADDR_BROADCAST;
else
ia->ia_broadaddr.sin_addr.s_addr =
htonl(ia->ia_subnet | ~ia->ia_subnetmask);
} else if (ifp->if_flags & IFF_LOOPBACK) {
ia->ia_dstaddr = ia->ia_addr;
flags |= RTF_HOST;
@ -1230,9 +1233,11 @@ in_broadcast(struct in_addr in, struct ifnet *ifp)
if (ifa->ifa_addr->sa_family == AF_INET &&
(in.s_addr == ia->ia_broadaddr.sin_addr.s_addr ||
/*
* Check for old-style (host 0) broadcast.
* Check for old-style (host 0) broadcast, but
* taking into account that RFC 3021 obsoletes it.
*/
t == ia->ia_subnet) &&
(ia->ia_subnetmask != IN_RFC3021_MASK &&
t == ia->ia_subnet)) &&
/*
* Check for an all one subnetmask. These
* only exist when an interface gets a secondary

2
sys/netinet/in.h
View File

@ -392,6 +392,8 @@ __END_DECLS
#define IN_LOOPBACKNET 127 /* official! */
#define IN_RFC3021_MASK (u_int32_t)0xfffffffe
/*
* Options for use with [gs]etsockopt at the IP level.
* First word of comment is data type; bool is stored in int.