On Tue, Dec 1, 2015, at 14:20, Konstantin Shemyak wrote: > On 01.12.2015 12:15, Hannes Frederic Sowa wrote: > > Hello, > > > > On Thu, Nov 26, 2015, at 19:28, Konstantin Shemyak wrote: > >> 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? > > > > Very simple, I would like to see DF bit being enforced in case we have a > > static TTL. Parvin, any reasons you removed this code? It is currently > > the only way to make sure the network does not kill itself in an endless > > loop on configuration mistakes. > > This solution does not completely eliminate all network loops, as there > may be other routers in the loop which do not set the DF bit. But it is > true that this behavior is "we did all we could".
That is what I meant. We cannot care about other routers, at least Linux shouldn't be pinpointed down to be the problem. :) > My point was not to question its feasibility, but to make it similar > across GRE, IP-IP and SIT tunnels. I would send a patch to add it again if Parvin didn't have good reasons to remove it. Thanks, Hannes -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
