From 1b3c61dc1aebf5d3d6c3981ba3eedc1e66f3ecda Mon Sep 17 00:00:00 2001 From: Lorenzo Colitti Date: Tue, 13 May 2014 10:17:34 -0700 Subject: [PATCH] net: Use fwmark reflection in PMTU discovery. Currently, routing lookups used for Path PMTU Discovery in absence of a socket or on unmarked sockets use a mark of 0. This causes PMTUD not to work when using routing based on netfilter fwmark mangling and fwmark ip rules, such as: iptables -j MARK --set-mark 17 ip rule add fwmark 17 lookup 100 This patch causes these route lookups to use the fwmark from the received ICMP error when the fwmark_reflect sysctl is enabled. This allows the administrator to make PMTUD work by configuring appropriate fwmark rules to mark the inbound ICMP packets. Black-box tested using user-mode linux by pointing different fwmarks at routing tables egressing on different interfaces, and using iptables mangling to mark packets inbound on each interface with the interface's fwmark. ICMPv4 and ICMPv6 PMTU discovery work as expected when mark reflection is enabled and fail when it is disabled. Signed-off-by: Lorenzo Colitti Signed-off-by: David S. Miller --- net/ipv4/route.c | 7 +++++++ net/ipv6/route.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index db1e0da871f4..50e1e0feddfc 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -993,6 +993,9 @@ void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu, struct flowi4 fl4; struct rtable *rt; + if (!mark) + mark = IP4_REPLY_MARK(net, skb->mark); + __build_flow_key(&fl4, NULL, iph, oif, RT_TOS(iph->tos), protocol, mark, flow_flags); rt = __ip_route_output_key(net, &fl4); @@ -1010,6 +1013,10 @@ static void __ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu) struct rtable *rt; __build_flow_key(&fl4, sk, iph, 0, 0, 0, 0, 0); + + if (!fl4.flowi4_mark) + fl4.flowi4_mark = IP4_REPLY_MARK(sock_net(sk), skb->mark); + rt = __ip_route_output_key(sock_net(sk), &fl4); if (!IS_ERR(rt)) { __ip_rt_update_pmtu(rt, &fl4, mtu); diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 004fffb6c221..f0a8ff9ed891 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1176,7 +1176,7 @@ void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu, memset(&fl6, 0, sizeof(fl6)); fl6.flowi6_oif = oif; - fl6.flowi6_mark = mark; + fl6.flowi6_mark = mark ? mark : IP6_REPLY_MARK(net, skb->mark); fl6.daddr = iph->daddr; fl6.saddr = iph->saddr; fl6.flowlabel = ip6_flowinfo(iph); -- 2.20.1