From 6d0722a2cec2c23db3b0855ff8bb433175a16b44 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 29 Sep 2010 23:35:10 -0700 Subject: [PATCH] ip_gre: comments change HARD_TX_LOCK no longer protects tunnels from dead loops, but xmit_recursion percpu counter. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ip_gre.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 035db6350037..fbe2c473a06a 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -64,13 +64,13 @@ We cannot track such dead loops during route installation, it is infeasible task. The most general solutions would be to keep skb->encapsulation counter (sort of local ttl), - and silently drop packet when it expires. It is the best + and silently drop packet when it expires. It is a good solution, but it supposes maintaing new variable in ALL skb, even if no tunneling is used. - Current solution: HARD_TX_LOCK lock breaks dead loops. - - + Current solution: xmit_recursion breaks dead loops. This is a percpu + counter, since when we enter the first ndo_xmit(), cpu migration is + forbidden. We force an exit if this counter reaches RECURSION_LIMIT 2. Networking dead loops would not kill routers, but would really kill network. IP hop limit plays role of "t->recursion" in this case, -- 2.30.2