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add some comments while trying to understand why appletalk

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gets some things wrong.
(part of my continuing "comment it as you understand it" effort :)
This commit is contained in:
Julian Elischer 1997-08-22 22:47:27 +00:00
parent 29ae2e935b
commit 7e2a6151f5
1 changed files with 36 additions and 4 deletions
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40
sys/net/if.c
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@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)if.c 8.3 (Berkeley) 1/4/94
* $Id: if.c,v 1.48 1997/05/03 21:07:13 peter Exp $
* $Id: if.c,v 1.49 1997/07/07 17:36:06 julian Exp $
*/
#include <sys/param.h>
@ -235,32 +235,64 @@ ifa_ifwithnet(addr)
u_int af = addr->sa_family;
char *addr_data = addr->sa_data, *cplim;
/*
* AF_LINK addresses can be looked up directly by their index number,
* so do that if we can.
*/
if (af == AF_LINK) {
register struct sockaddr_dl *sdl = (struct sockaddr_dl *)addr;
if (sdl->sdl_index && sdl->sdl_index <= if_index)
return (ifnet_addrs[sdl->sdl_index - 1]);
}
/*
* Scan though each interface, looking for ones that have
* addresses in this address family.
*/
for (ifp = ifnet.tqh_first; ifp; ifp = ifp->if_link.tqe_next) {
for (ifa = ifp->if_addrhead.tqh_first; ifa;
ifa = ifa->ifa_link.tqe_next) {
register char *cp, *cp2, *cp3;
if (ifa->ifa_addr->sa_family != af)
next: continue;
next: continue;
if (ifp->if_flags & IFF_POINTOPOINT) {
/*
* This is a bit broken as it doesn't
* take into account that the remote end may
* be a single node in the network we are
* looking for.
* The trouble is that we don't know the
* netmask for the remote end.
*/
if (ifa->ifa_dstaddr != 0
&& equal(addr, ifa->ifa_dstaddr))
return (ifa);
} else {
/*
* Scan all the bits in the ifa's address.
* If a bit dissagrees with what we are
* looking for, mask it with the netmask
* to see if it really matters.
* (A byte at a time)
*/
if (ifa->ifa_netmask == 0)
continue;
cp = addr_data;
cp2 = ifa->ifa_addr->sa_data;
cp3 = ifa->ifa_netmask->sa_data;
cplim = ifa->ifa_netmask->sa_len + (char *)ifa->ifa_netmask;
cplim = ifa->ifa_netmask->sa_len
+ (char *)ifa->ifa_netmask;
while (cp3 < cplim)
if ((*cp++ ^ *cp2++) & *cp3++)
goto next;
goto next; /* next address! */
/*
* If the netmask of what we just found
* is more specific than what we had before
* (if we had one) then remember the new one
* before continuing to search
* for an even better one.
*/
if (ifa_maybe == 0 ||
rn_refines((caddr_t)ifa->ifa_netmask,
(caddr_t)ifa_maybe->ifa_netmask))