On 05/12/15(Sat) 13:07, Vincent Gross wrote:
> in6_selectsrc() uses two different rtalloc calls depending on whether or
> not the destination address is multicast or not, but there is nothing to
> explain why. I dug a bit and found this commit from itojun@ :
>
> diff -u -r1.6 -r1.7
> --- src/sys/netinet6/in6_src.c 2000/06/18 04:49:32 1.6
> +++ src/sys/netinet6/in6_src.c 2000/06/18 17:02:59 1.7
> @@ -244,7 +244,11 @@
> ro->ro_dst.sin6_family = AF_INET6;
> ro->ro_dst.sin6_len = sizeof(struct sockaddr_in6);
> ro->ro_dst.sin6_addr = *dst;
> - if (!IN6_IS_ADDR_MULTICAST(dst)) {
> + ro->ro_dst.sin6_scope_id = dstsock->sin6_scope_id;
> + if (IN6_IS_ADDR_MULTICAST(dst)) {
> + ro->ro_rt = rtalloc1(&((struct route *)ro)
> + ->ro_dst, 0);
> + } else {
> rtalloc((struct route *)ro);
> }
> }
>
> Below are rtalloc() and rtalloc1() from sys/net/route.c r1.19 commited
> on 05/21/2000 :
>
> > void
> > rtalloc(ro)
> > register struct route *ro;
> > {
> > if (ro->ro_rt && ro->ro_rt->rt_ifp && (ro->ro_rt->rt_flags & RTF_UP))
> > return; /* XXX */
> > ro->ro_rt = rtalloc1(&ro->ro_dst, 1);
> > }
> >
> > struct rtentry *
> > rtalloc1(dst, report)
> > register struct sockaddr *dst;
> > int report;
> > {
> [...]
> > /*
> > * IP encapsulation does lots of lookups where we don't need nor want
> > * the RTM_MISSes that would be generated. It causes RTM_MISS storms
> > * sent upward breaking user-level routing queries.
> > */
> > miss: if (report && dst->sa_family != PF_KEY) {
> > bzero((caddr_t)&info, sizeof(info));
> > info.rti_info[RTAX_DST] = dst;
> > rt_missmsg(msgtype, &info, 0, err);
> > }
> > }
> > splx(s);
> > return (newrt);
> > }
>
>
> So this if(MULTICAST) has been introduced to prevent RTM_MISS storms when
> looking up routes to multicast addresses ; multicast and unicast route lookups
> are the same.
>
> Also, rtalloc(foo, RT_RESOLVE, bar) and rtalloc_mpath(foo, NULL, bar) are both
> equivalent to _rtalloc(foo, NULL, RT_RESOLVE, bar).
>
> Let's remove this if(MULTICAST), it's just confusing.
>
> ok ?
ok mpi@
>
> Index: sys/netinet6/in6_src.c
> ===================================================================
> RCS file: /cvs/src/sys/netinet6/in6_src.c,v
> retrieving revision 1.71
> diff -u -p -r1.71 in6_src.c
> --- sys/netinet6/in6_src.c 2 Dec 2015 13:29:26 -0000 1.71
> +++ sys/netinet6/in6_src.c 5 Dec 2015 12:03:48 -0000
> @@ -240,13 +240,8 @@ in6_selectsrc(struct in6_addr **in6src,
> sa6->sin6_len = sizeof(struct sockaddr_in6);
> sa6->sin6_addr = *dst;
> sa6->sin6_scope_id = dstsock->sin6_scope_id;
> - if (IN6_IS_ADDR_MULTICAST(dst)) {
> - ro->ro_rt = rtalloc(sin6tosa(&ro->ro_dst),
> - RT_RESOLVE, ro->ro_tableid);
> - } else {
> - ro->ro_rt = rtalloc_mpath(sin6tosa(&ro->ro_dst),
> - NULL, ro->ro_tableid);
> - }
> + ro->ro_rt = rtalloc(sin6tosa(&ro->ro_dst),
> + RT_RESOLVE, ro->ro_tableid);
> }
>
> /*
>
