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Date: Thu, 07 Jan 2010 17:10:15 -0800 (PST)
From: David Miller <davem@...emloft.net>
To: zenczykowski@...il.com
Cc: therbert@...gle.com, netdev@...r.kernel.org, lorenzo@...gle.com
Subject: Re: [PATCH] IPv6: fix rt_lookup in pmtu_discovery
From: Maciej Żenczykowski <zenczykowski@...il.com>
Date: Thu, 7 Jan 2010 17:05:36 -0800
> I've spoken with Tom and we can't quite seem to figure out what
> exactly the code should be attempting to accomplish here.
"git blame net/ipv4/route.c >x.c" might help you solve that
mystery, here is one example of what it might show you:
commit 0010e46577a27c1d915034637f6c2fa57a9a091c
Author: Timo Teras <timo.teras@....fi>
Date: Tue Apr 29 03:32:25 2008 -0700
ipv4: Update MTU to all related cache entries in ip_rt_frag_needed()
Add struct net_device parameter to ip_rt_frag_needed() and update MTU to
cache entries where ifindex is specified. This is similar to what is
already done in ip_rt_redirect().
Signed-off-by: Timo Teras <timo.teras@....fi>
Signed-off-by: David S. Miller <davem@...emloft.net>
diff --git a/include/net/route.h b/include/net/route.h
index c633880..fc836ff 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -116,7 +116,7 @@ extern int __ip_route_output_key(struct net *, struct rtable **, const struct f
extern int ip_route_output_key(struct net *, struct rtable **, struct flowi *flp);
extern int ip_route_output_flow(struct net *, struct rtable **rp, struct flowi *flp, struct sock *sk, int flags);
extern int ip_route_input(struct sk_buff*, __be32 dst, __be32 src, u8 tos, struct net_device *devin);
-extern unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph, unsigned short new_mtu);
+extern unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph, unsigned short new_mtu, struct net_device *dev);
extern void ip_rt_send_redirect(struct sk_buff *skb);
extern unsigned inet_addr_type(struct net *net, __be32 addr);
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index c67d00e..8739735 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -691,7 +691,8 @@ static void icmp_unreach(struct sk_buff *skb)
NIPQUAD(iph->daddr));
} else {
info = ip_rt_frag_needed(net, iph,
- ntohs(icmph->un.frag.mtu));
+ ntohs(icmph->un.frag.mtu),
+ skb->dev);
if (!info)
goto out;
}
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index ce25a13..5e3685c 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1430,11 +1430,13 @@ static inline unsigned short guess_mtu(unsigned short old_mtu)
}
unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
- unsigned short new_mtu)
+ unsigned short new_mtu,
+ struct net_device *dev)
{
- int i;
+ int i, k;
unsigned short old_mtu = ntohs(iph->tot_len);
struct rtable *rth;
+ int ikeys[2] = { dev->ifindex, 0 };
__be32 skeys[2] = { iph->saddr, 0, };
__be32 daddr = iph->daddr;
unsigned short est_mtu = 0;
@@ -1442,22 +1444,26 @@ unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
if (ipv4_config.no_pmtu_disc)
return 0;
- for (i = 0; i < 2; i++) {
- unsigned hash = rt_hash(daddr, skeys[i], 0);
+ for (k = 0; k < 2; k++) {
+ for (i = 0; i < 2; i++) {
+ unsigned hash = rt_hash(daddr, skeys[i], ikeys[k]);
- rcu_read_lock();
- for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
- rth = rcu_dereference(rth->u.dst.rt_next)) {
- if (rth->fl.fl4_dst == daddr &&
- rth->fl.fl4_src == skeys[i] &&
- rth->rt_dst == daddr &&
- rth->rt_src == iph->saddr &&
- rth->fl.iif == 0 &&
- !(dst_metric_locked(&rth->u.dst, RTAX_MTU)) &&
- net_eq(dev_net(rth->u.dst.dev), net) &&
- rth->rt_genid == atomic_read(&rt_genid)) {
+ rcu_read_lock();
+ for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
+ rth = rcu_dereference(rth->u.dst.rt_next)) {
unsigned short mtu = new_mtu;
+ if (rth->fl.fl4_dst != daddr ||
+ rth->fl.fl4_src != skeys[i] ||
+ rth->rt_dst != daddr ||
+ rth->rt_src != iph->saddr ||
+ rth->fl.oif != ikeys[k] ||
+ rth->fl.iif != 0 ||
+ dst_metric_locked(&rth->u.dst, RTAX_MTU) ||
+ !net_eq(dev_net(rth->u.dst.dev), net) ||
+ rth->rt_genid != atomic_read(&rt_genid))
+ continue;
+
if (new_mtu < 68 || new_mtu >= old_mtu) {
/* BSD 4.2 compatibility hack :-( */
@@ -1483,8 +1489,8 @@ unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
est_mtu = mtu;
}
}
+ rcu_read_unlock();
}
- rcu_read_unlock();
}
return est_mtu ? : new_mtu;
}
--
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