Subject: Re: PROBLEM: Linux kernel 2.6.31 IPv4 TCP fails to open huge amount of outgoing connections (unable to bind ... )

From: Evgeniy Polyakov <[email-masked]>
Date: Wed, 21 Apr 2010 13:58:12 +0400

On Wed, Apr 21, 2010 at 11:02:15AM +0200, Eric Dumazet ([email-masked]) wrote:
> Le mercredi 21 avril 2010 à 12:25 +0400, Evgeniy Polyakov a écrit :
> 
> > I believe this is a useful patch, but it addresses a different issue.
> > This path should not fire up when we bind to single address.
> 
> Well, the real problem is that following sequence can happen :
> 
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 5
> setsockopt(5, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(5, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(5, {sa_family=AF_INET, sin_port=htons(34000), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 6
> setsockopt(6, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(6, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(6, {sa_family=AF_INET, sin_port=htons(34002), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 7
> setsockopt(7, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(7, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(7, {sa_family=AF_INET, sin_port=htons(34001), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 8
> setsockopt(8, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(8, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(8, {sa_family=AF_INET, sin_port=htons(34002), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 9
> setsockopt(9, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(9, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(9, {sa_family=AF_INET, sin_port=htons(34000), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 10
> setsockopt(10, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(10, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(10, {sa_family=AF_INET, sin_port=htons(34002), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 11
> setsockopt(11, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> bind(11, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("127.0.0.2")}, 16) = 0
> getsockname(11, {sa_family=AF_INET, sin_port=htons(34001), sin_addr=inet_addr("127.0.0.2")}, [16]) = 0
> 
> 
> Note ports are given several times for different sockets.
> 
> So several sockets are 'bound' to same IP:port values

That's kind of weird, since address is the same. I'm curious why bind
conflict does not resolve that. Likely because socket is not yet
connected.

> At connect() time, we refuse and say address is not available.

Yup. But isn't it a different problem from what Gaspar observed?
Netcat connects after bind so it should not be an issue here.

-- 
	Evgeniy Polyakov