From 6d7956e8013d8b162ecdc4f497aaf69b78b5e0e8 Mon Sep 17 00:00:00 2001 From: jmg Date: Sun, 10 Sep 2006 17:49:09 +0000 Subject: make use of the host route's mtu for processing. This means we can now 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. --- sys/netinet/ip_output.c | 43 +++++++++++++++++++++++++------------------ 1 file changed, 25 insertions(+), 18 deletions(-) (limited to 'sys/netinet/ip_output.c') diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c index 8311732..f37c993 100644 --- a/sys/netinet/ip_output.c +++ b/sys/netinet/ip_output.c @@ -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 @@ again: 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 @@ again: 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 @@ again: */ #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 @@ again: 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 @@ passout: * 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 @@ passout: /* 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 @@ passout: * 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) { -- cgit v1.1