Messages in this thread | | | Date | Sun, 6 Oct 2013 17:13:51 +0200 | From | Hannes Frederic Sowa <> | Subject | Re: [PATCH] Fix the upper MTU limit in ipv6 GRE tunnel |
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On Sun, Oct 06, 2013 at 03:42:15PM +0100, Oussama Ghorbel wrote: > The initialization in ip6gre_tnl_link_config is done as the following: > static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu) > { > ... > int addend = sizeof(struct ipv6hdr) + 4; > ... > /* Precalculate GRE options length */ > if (t->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) { > if (t->parms.o_flags&GRE_CSUM) > addend += 4; > if (t->parms.o_flags&GRE_KEY) > addend += 4; > if (t->parms.o_flags&GRE_SEQ) > addend += 4; > } > ... > dev->hard_header_len = rt->dst.dev->hard_header_len + addend; > ... > t->hlen = addend; > .. > } > > Unless they are other reasons, the hard_header_len is taken into > account the GRE_KEY, GRE_SEQ ..
But only if a new route is found. The hard_header_len reinitialization is guarded by a (rt == NULL). We may have not found one on boot up.
> > To make this correct we would have to refactor the usage of the variables a > > bit as is done in ipv4/ip_tunnel.c. The safest thing would be to leave this > > check as-is currently although we exclude some allowed mtus. > > > > Perhaps you want to take a look how to achieve that? ;) > > > Why not, consistency is good ...
Thanks,
Hannes
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