From: Konstantin Shemyak <konstantin@shemyak.com>
To: "netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: IPv4 tunnels: why IP-IP and SIT enforce DF bit, but GRE does not?
Date: Thu, 26 Nov 2015 20:28:02 +0200 [thread overview]
Message-ID: <56574F32.6070706@shemyak.com> (raw)
The kernel has taken the decision to always enforce DF bit on IPv4
tunnels, which have fixed (not inherited) TTL (e.g.
net/ipv4/ipip.c:ipip_tunnel_ioctl()). Commment by Alexey Kuznetsov in
the head of ip_gre.c explains that the reason is attempting to avoid
network loops.
But the commit c54419321455631 removed this enforcing from GRE tunnels,
not changing this behavior for IP-IP (net/ipv4/ipip.c) and SIT
(net/ipv6/sit.c).
It can be discussed whether such enforcing of DF bit is exactly the
desired behavior, but shouldn't it at least be identical across IPv4
tunnels?
Konstantin Shemyak
next reply other threads:[~2015-11-26 18:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-26 18:28 Konstantin Shemyak [this message]
2015-12-01 10:15 ` IPv4 tunnels: why IP-IP and SIT enforce DF bit, but GRE does not? Hannes Frederic Sowa
2015-12-01 13:20 ` Konstantin Shemyak
2015-12-01 13:30 ` Hannes Frederic Sowa
2015-12-01 17:08 ` David Miller
2015-12-05 15:24 ` Konstantin Shemyak
2015-12-05 18:07 ` David Miller
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