diff options
Diffstat (limited to 'sys/netinet/ip_icmp.c')
| -rw-r--r-- | sys/netinet/ip_icmp.c | 82 |
1 files changed, 81 insertions, 1 deletions
diff --git a/sys/netinet/ip_icmp.c b/sys/netinet/ip_icmp.c index 14b763e4f329..507d770001e3 100644 --- a/sys/netinet/ip_icmp.c +++ b/sys/netinet/ip_icmp.c @@ -31,7 +31,7 @@ * SUCH DAMAGE. * * @(#)ip_icmp.c 8.2 (Berkeley) 1/4/94 - * $Id: ip_icmp.c,v 1.8 1995/07/10 16:16:00 wollman Exp $ + * $Id: ip_icmp.c,v 1.9 1995/08/29 17:49:04 wollman Exp $ */ #include <sys/param.h> @@ -302,6 +302,46 @@ icmp_input(m, hlen) printf("deliver to protocol %d\n", icp->icmp_ip.ip_p); #endif icmpsrc.sin_addr = icp->icmp_ip.ip_dst; +#ifdef MTUDISC + /* + * MTU discovery: + * If we got a needfrag and there is a host route to the + * original destination, and the MTU is not locked, then + * set the MTU in the route to the suggested new value + * (if given) and then notify as usual. The ULPs will + * notice that the MTU has changed and adapt accordingly. + * If no new MTU was suggested, then we guess a new one + * less than the current value. If the new MTU is + * unreasonably small (arbitrarily set at 296), then + * we reset the MTU to the interface value and enable the + * lock bit, indicating that we are no longer doing MTU + * discovery. + */ + if (code == PRC_MSGSIZE) { + struct rtentry *rt; + int mtu; + + rt = rtalloc1((struct sockaddr *)&icmpsrc, 0, + RTF_CLONING | RTF_PRCLONING); + if (rt && (rt->rt_flags & RTF_HOST) + && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { + mtu = ntohs(icp->icmp_nextmtu); + if (!mtu) + mtu = ip_next_mtu(rt->rt_rmx.rmx_mtu, + 1); + if (!mtu || mtu < 296) { + rt->rt_rmx.rmx_mtu = + rt->rt_ifp->if_mtu; + rt->rt_rmx.rmx_locks |= RTV_MTU; + } else if (rt->rt_rmx.rmx_mtu > mtu) { + rt->rt_rmx.rmx_mtu = mtu; + } + } + if (rt) + RTFREE(rt); + } + +#endif /* MTUDISC */ ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput; if (ctlfunc) (*ctlfunc)(code, (struct sockaddr *)&icmpsrc, @@ -612,3 +652,43 @@ icmp_sysctl(name, namelen, oldp, oldlenp, newp, newlen) } /* NOTREACHED */ } + +#ifdef MTUDISC +/* + * Return the next larger or smaller MTU plateau (table from RFC 1191) + * given current value MTU. If DIR is less than zero, a larger plateau + * is returned; otherwise, a smaller value is returned. + */ +int +ip_next_mtu(mtu, dir) + int mtu; + int dir; +{ + static int mtutab[] = { + 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1006, 508, 296, + 68, 0 + }; + int i; + + for (i = 0; i < (sizeof mtutab) / (sizeof mtutab[0]); i++) { + if (mtu >= mtutab[i]) + break; + } + + if (dir < 0) { + if (i == 0) { + return 0; + } else { + return mtutab[i - 1]; + } + } else { + if (mtutab[i] == 0) { + return 0; + } else if(mtu > mtutab[i]) { + return mtutab[i]; + } else { + return mtutab[i + 1]; + } + } +} +#endif /* MTUDISC */ |