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make use of the host route's mtu for processing. This means we can now

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support a network w/ split mtu's by assigning each host route the correct
mtu.  an aspiring programmer could write a daemon to probe hosts and find
out if they support a larger mtu.
This commit is contained in:
John-Mark Gurney 2006-09-10 17:49:09 +00:00
parent 805def2e04
commit 3ae2ad088e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=162205
1 changed files with 25 additions and 18 deletions
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43
sys/netinet/ip_output.c
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@ -112,6 +112,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
struct ifnet *ifp = NULL; /* keep compiler happy */
struct mbuf *m0;
int hlen = sizeof (struct ip);
int mtu;
int len, error = 0;
struct sockaddr_in *dst = NULL; /* keep compiler happy */
struct in_ifaddr *ia = NULL;
@ -172,7 +173,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
dst->sin_family != AF_INET ||
dst->sin_addr.s_addr != ip->ip_dst.s_addr)) {
RTFREE(ro->ro_rt);
ro->ro_rt = (struct rtentry *)0;
ro->ro_rt = (struct rtentry *)NULL;
}
#ifdef IPFIREWALL_FORWARD
if (ro->ro_rt == NULL && fwd_tag == NULL) {
@ -241,6 +242,24 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
else
isbroadcast = in_broadcast(dst->sin_addr, ifp);
}
/*
* Calculate MTU. If we have a route that is up, use that,
* otherwise use the interface's MTU.
*/
if (ro->ro_rt->rt_flags & (RTF_UP | RTF_HOST)) {
/*
* This case can happen if the user changed the MTU
* of an interface after enabling IP on it. Because
* most netifs don't keep track of routes pointing to
* them, there is no way for one to update all its
* routes when the MTU is changed.
*/
if (ro->ro_rt->rt_rmx.rmx_mtu > ifp->if_mtu)
ro->ro_rt->rt_rmx.rmx_mtu = ifp->if_mtu;
mtu = ro->ro_rt->rt_rmx.rmx_mtu;
} else {
mtu = ifp->if_mtu;
}
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
struct in_multi *inm;
@ -360,10 +379,10 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
*/
#ifdef ALTQ
if ((!ALTQ_IS_ENABLED(&ifp->if_snd)) &&
((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >=
((ifp->if_snd.ifq_len + ip->ip_len / mtu + 1) >=
ifp->if_snd.ifq_maxlen))
#else
if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >=
if ((ifp->if_snd.ifq_len + ip->ip_len / mtu + 1) >=
ifp->if_snd.ifq_maxlen)
#endif /* ALTQ */
{
@ -388,7 +407,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
goto bad;
}
/* don't allow broadcast messages to be fragmented */
if (ip->ip_len > ifp->if_mtu) {
if (ip->ip_len > mtu) {
error = EMSGSIZE;
goto bad;
}
@ -497,7 +516,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
* If small enough for interface, or the interface will take
* care of the fragmentation for us, we can just send directly.
*/
if (ip->ip_len <= ifp->if_mtu ||
if (ip->ip_len <= mtu ||
(m->m_pkthdr.csum_flags & ifp->if_hwassist & CSUM_TSO) != 0 ||
((ip->ip_off & IP_DF) == 0 && (ifp->if_hwassist & CSUM_FRAGMENT))) {
ip->ip_len = htons(ip->ip_len);
@ -542,18 +561,6 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
/* Balk when DF bit is set or the interface didn't support TSO. */
if ((ip->ip_off & IP_DF) || (m->m_pkthdr.csum_flags & CSUM_TSO)) {
error = EMSGSIZE;
/*
* This case can happen if the user changed the MTU
* of an interface after enabling IP on it. Because
* most netifs don't keep track of routes pointing to
* them, there is no way for one to update all its
* routes when the MTU is changed.
*/
if (ro != NULL &&
(ro->ro_rt->rt_flags & (RTF_UP | RTF_HOST)) &&
(ro->ro_rt->rt_rmx.rmx_mtu > ifp->if_mtu)) {
ro->ro_rt->rt_rmx.rmx_mtu = ifp->if_mtu;
}
ipstat.ips_cantfrag++;
goto bad;
}
@ -562,7 +569,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
* Too large for interface; fragment if possible. If successful,
* on return, m will point to a list of packets to be sent.
*/
error = ip_fragment(ip, &m, ifp->if_mtu, ifp->if_hwassist, sw_csum);
error = ip_fragment(ip, &m, mtu, ifp->if_hwassist, sw_csum);
if (error)
goto bad;
for (; m; m = m0) {