netdev - Re: regression when connecting to ipv6 localhost

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Date:	Mon, 15 Oct 2012 11:25:36 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jan Hinnerk Stosch <janhinnerk.stosch@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: regression when connecting to ipv6 localhost

On Mon, 2012-10-15 at 07:42 +0200, Eric Dumazet wrote:
> On Mon, 2012-10-15 at 00:11 +0200, Jan Hinnerk Stosch wrote:
> > 2012/10/15 Eric Dumazet <eric.dumazet@...il.com>:
> > > Please add -f to follow children
> > >
> > > strace -o /tmp/STRACE -f /usr/bin/ntpd -g -u ntp:ntp
> > >
> > >
> > 
> > Ok, done.
> 
> # grep bind STRACE
> 
> 
> 
> 12928 bind(16, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
> 12928 bind(17, {sa_family=AF_INET6, sin6_port=htons(123), inet_pton(AF_INET6, "::", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0}, 28) = 0
> 
> (These two binds are the wildcards to drop ipv4/ipv6 packets sent on other addresses than
>  the following :)
> 
> 12928 bind(18, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
> 12928 bind(19, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("192.168.178.27")}, 16) = 0
> 12928 bind(20, {sa_family=AF_INET6, sin6_port=htons(123), inet_pton(AF_INET6, "fe80::922b:34ff:fe33:c292", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=if_nametoindex("eth0")}, 28) = 0
> 12928 bind(21, {sa_family=AF_NETLINK, pid=0, groups=00000771}, 12) = 0
> 
> So ntpd doesnt listen on ntp messages sent on ::1
> 
> 

Hmm, another strange thing in your STRACE file is :


12928 open("/proc/net/if_inet6", O_RDONLY) = 6
12928 fstat(6, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
12928 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7fc54a719000
12928 lseek(6, 0, SEEK_SET)             = 0
12928 read(6, "fe80000000000000922b34fffe33c292"..., 1024) = 54


So /proc/net/if_inet6 doesnt include lo device on your machine ?



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