gre: fix spelling in comments

   it is infeasible task. The most general solutions would be

   to keep skb->encapsulation counter (sort of local ttl),

   and silently drop packet when it expires. It is a good

   solution, but it supposes maintaing new variable in ALL

   solution, but it supposes maintaining new variable in ALL

   skb, even if no tunneling is used.

   Current solution: xmit_recursion breaks dead loops. This is a percpu

   One of them is to parse packet trying to detect inner encapsulation

   made by our node. It is difficult or even impossible, especially,

   taking into account fragmentation. TO be short, tt is not solution at all.

   taking into account fragmentation. TO be short, ttl is not solution at all.

   Current solution: The solution was UNEXPECTEDLY SIMPLE.

   We force DF flag on tunnels with preconfigured hop limit,

   that is ALL. :-) Well, it does not remove the problem completely,

   but exponential growth of network traffic is changed to linear

   (branches, that exceed pmtu are pruned) and tunnel mtu

   fastly degrades to value <68, where looping stops.

   rapidly degrades to value <68, where looping stops.

   Yes, it is not good if there exists a router in the loop,

   which does not force DF, even when encapsulating packets have DF set.

   But it is not our problem! Nobody could accuse us, we made

   GRE tunnels with enabled checksum. Tell them "thank you".

   Well, I wonder, rfc1812 was written by Cisco employee,

   what the hell these idiots break standrads established

   by themself???

   what the hell these idiots break standards established

   by themselves???

 */

	const struct iphdr *iph = (const struct iphdr *)skb->data;