Commit 22441cfa authored Oct 15, 2008 by Pedro Ribeiro Committed by David S. Miller Oct 15, 2008

IPV6: Fix default gateway criteria wrt. HIGH/LOW preference radv option



Problem observed:
               In IPv6, in the presence of multiple routers candidates to
               default gateway in one segment, each sending a different
               value of preference, the Linux hosts connected to the
               segment weren't selecting the right one in all the
               combinations possible of LOW/MEDIUM/HIGH preference.

This patch changes two files:
include/linux/icmpv6.h
               Get the "router_pref" bitfield in the right place
               (as RFC4191 says), named the bit left with this fix as
               "home_agent" (RFC3775 say that's his function)

net/ipv6/ndisc.c
               Corrects the binary logic behind the updating of the
               router preference in the flags of the routing table

Result:
               With this two fixes applied, the default route used by
               the system was to consistent with the rules mentioned
               in RFC4191 in case of changes in the value of preference
               in router advertisements

Signed-off-by: Pedro Ribeiro <pribeiro@net.ipl.pt>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent deb28d9b

include/linux/icmpv6.h

+4 −2

Original line number	Diff line number	Diff line
		@@ -40,16 +40,18 @@ struct icmp6hdr {
		struct icmpv6_nd_ra {
		__u8 hop_limit;
		#if defined(__LITTLE_ENDIAN_BITFIELD)
		__u8 reserved:4,
		__u8 reserved:3,
		router_pref:2,
		home_agent:1,
		other:1,
		managed:1;

		#elif defined(__BIG_ENDIAN_BITFIELD)
		__u8 managed:1,
		other:1,
		home_agent:1,
		router_pref:2,
		reserved:4;
		reserved:3;
		#else
		#error "Please fix <asm/byteorder.h>"
		#endif

net/ipv6/ndisc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1199,7 +1199,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
		}
		neigh->flags \|= NTF_ROUTER;
		} else if (rt) {
		rt->rt6i_flags \|= (rt->rt6i_flags & ~RTF_PREF_MASK) \| RTF_PREF(pref);
		rt->rt6i_flags = (rt->rt6i_flags & ~RTF_PREF_MASK) \| RTF_PREF(pref);
		}

		if (rt)

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