net: fix inet_getid() and ipv6_select_ident() bugs (39c36094) · Commits · 戴 / test

I noticed we were sending wrong IPv4 ID in TCP flows when MTU discovery is disabled. Note how GSO/TSO packets do not have monotonically incrementing ID. 06:37:41.575531 IP (id 14227, proto: TCP (6), length: 4396) 06:37:41.575534 IP (id 14272, proto: TCP (6), length: 65212) 06:37:41.575544 IP (id 14312, proto: TCP (6), length: 57972) 06:37:41.575678 IP (id 14317, proto: TCP (6), length: 7292) 06:37:41.575683 IP (id 14361, proto: TCP (6), length: 63764) It appears I introduced this bug in linux-3.1. inet_getid() must return the old value of peer->ip_id_count, not the new one. Lets revert this part, and remove the prevention of a null identification field in IPv6 Fragment Extension Header, which is dubious and not even done properly. Fixes: ("ipv6: make fragment identifications less predictable") Signed-off-by:

Eric Dumazet <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/net/inetpeer.h

+1 −8

Original line number	Diff line number	Diff line
		@@ -177,16 +177,9 @@ static inline void inet_peer_refcheck(const struct inet_peer *p)
		/* can be called with or without local BH being disabled */
		static inline int inet_getid(struct inet_peer *p, int more)
		{
		int old, new;
		more++;
		inet_peer_refcheck(p);
		do {
		old = atomic_read(&p->ip_id_count);
		new = old + more;
		if (!new)
		new = 1;
		} while (atomic_cmpxchg(&p->ip_id_count, old, new) != old);
		return new;
		return atomic_add_return(more, &p->ip_id_count) - more;
		}

		#endif /* _NET_INETPEER_H */

net/ipv6/output_core.c

+3 −8

Original line number	Diff line number	Diff line
		@@ -12,7 +12,7 @@ void ipv6_select_ident(struct frag_hdr fhdr, struct rt6_info rt)
		{
		static atomic_t ipv6_fragmentation_id;
		struct in6_addr addr;
		int old, new;
		int ident;

		#if IS_ENABLED(CONFIG_IPV6)
		struct inet_peer *peer;
		@@ -26,15 +26,10 @@ void ipv6_select_ident(struct frag_hdr fhdr, struct rt6_info rt)
		return;
		}
		#endif
		do {
		old = atomic_read(&ipv6_fragmentation_id);
		new = old + 1;
		if (!new)
		new = 1;
		} while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old);
		ident = atomic_inc_return(&ipv6_fragmentation_id);

		addr = rt->rt6i_dst.addr;
		addr.s6_addr32[0] ^= (__force __be32)new;
		addr.s6_addr32[0] ^= (__force __be32)ident;
		fhdr->identification = htonl(secure_ipv6_id(addr.s6_addr32));
		}
		EXPORT_SYMBOL(ipv6_select_ident);

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