From 22441cfa0c70dcd457f3c081fcf285c3bd155824 Mon Sep 17 00:00:00 2001 From: Pedro Ribeiro Date: Wed, 15 Oct 2008 15:47:49 -0700 Subject: [PATCH] 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 Acked-by: YOSHIFUJI Hideaki Signed-off-by: David S. Miller --- include/linux/icmpv6.h | 6 ++++-- net/ipv6/ndisc.c | 2 +- 2 files changed, 5 insertions(+), 3 deletions(-) diff --git a/include/linux/icmpv6.h b/include/linux/icmpv6.h index 03067443198..a93a8dd3311 100644 --- a/include/linux/icmpv6.h +++ b/include/linux/icmpv6.h @@ -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 " #endif diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 840b15780a3..aae7ddcc8a2 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -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) -- 2.41.1