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Avoid doing multiple route lookups for the same destination IP during forwarding

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ip_forward() does a route lookup for testing this packet can be sent to a known destination,
it also can do another route lookup if it detects that an ICMP redirect is needed,
it forgets all of this and handovers to ip_output() to do the same lookup yet again.

This optimisation just does one route lookup during the forwarding path and handovers that to be considered by ip_output().

Differential Revision:	https://reviews.freebsd.org/D2964
Approved by:	ae, gnn(mentor)
MFC after:	1 week
This commit is contained in:
Ermal Luçi 2015-07-02 18:10:41 +00:00
parent d32a66b2a2
commit d14122b078
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=285051
1 changed files with 18 additions and 17 deletions
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35
sys/netinet/ip_input.c
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@ -897,6 +897,7 @@ ip_forward(struct mbuf *m, int srcrt)
struct ip *ip = mtod(m, struct ip *);
struct in_ifaddr *ia;
struct mbuf *mcopy;
struct sockaddr_in *sin;
struct in_addr dest;
struct route ro;
int error, type = 0, code = 0, mtu = 0;
@ -925,7 +926,22 @@ ip_forward(struct mbuf *m, int srcrt)
}
#endif
ia = ip_rtaddr(ip->ip_dst, M_GETFIB(m));
bzero(&ro, sizeof(ro));
sin = (struct sockaddr_in *)&ro.ro_dst;
sin->sin_family = AF_INET;
sin->sin_len = sizeof(*sin);
sin->sin_addr = ip->ip_dst;
#ifdef RADIX_MPATH
rtalloc_mpath_fib(&ro,
ntohl(ip->ip_src.s_addr ^ ip->ip_dst.s_addr),
M_GETFIB(m));
#else
in_rtalloc_ign(&ro, 0, M_GETFIB(m));
#endif
if (ro.ro_rt != NULL) {
ia = ifatoia(ro.ro_rt->rt_ifa);
ifa_ref(&ia->ia_ifa);
}
#ifndef IPSEC
/*
* 'ia' may be NULL if there is no route for this destination.
@ -934,6 +950,7 @@ ip_forward(struct mbuf *m, int srcrt)
*/
if (!srcrt && ia == NULL) {
icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
RO_RTFREE(&ro);
return;
}
#endif
@ -990,16 +1007,8 @@ ip_forward(struct mbuf *m, int srcrt)
dest.s_addr = 0;
if (!srcrt && V_ipsendredirects &&
ia != NULL && ia->ia_ifp == m->m_pkthdr.rcvif) {
struct sockaddr_in *sin;
struct rtentry *rt;
bzero(&ro, sizeof(ro));
sin = (struct sockaddr_in *)&ro.ro_dst;
sin->sin_family = AF_INET;
sin->sin_len = sizeof(*sin);
sin->sin_addr = ip->ip_dst;
in_rtalloc_ign(&ro, 0, M_GETFIB(m));
rt = ro.ro_rt;
if (rt && (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0 &&
@ -1018,16 +1027,8 @@ ip_forward(struct mbuf *m, int srcrt)
code = ICMP_REDIRECT_HOST;
}
}
if (rt)
RTFREE(rt);
}
/*
* Try to cache the route MTU from ip_output so we can consider it for
* the ICMP_UNREACH_NEEDFRAG "Next-Hop MTU" field described in RFC1191.
*/
bzero(&ro, sizeof(ro));
error = ip_output(m, NULL, &ro, IP_FORWARDING, NULL, NULL);
if (error == EMSGSIZE && ro.ro_rt)