From 619d48665f45c3a9ccadd8cf171cb8ce230900ec Mon Sep 17 00:00:00 2001 From: Hangbin Liu Date: Thu, 30 Jul 2015 14:28:42 +0800 Subject: [PATCH] net/ipv6: add sysctl option accept_ra_min_hop_limit [ Upstream commit 8013d1d7eafb0589ca766db6b74026f76b7f5cb4 ] Commit 6fd99094de2b ("ipv6: Don't reduce hop limit for an interface") disabled accept hop limit from RA if it is smaller than the current hop limit for security stuff. But this behavior kind of break the RFC definition. RFC 4861, 6.3.4. Processing Received Router Advertisements A Router Advertisement field (e.g., Cur Hop Limit, Reachable Time, and Retrans Timer) may contain a value denoting that it is unspecified. In such cases, the parameter should be ignored and the host should continue using whatever value it is already using. If the received Cur Hop Limit value is non-zero, the host SHOULD set its CurHopLimit variable to the received value. So add sysctl option accept_ra_min_hop_limit to let user choose the minimum hop limit value they can accept from RA. And set default to 1 to meet RFC standards. Signed-off-by: Hangbin Liu Acked-by: YOSHIFUJI Hideaki Signed-off-by: David S. Miller [bwh: Backported to 3.2: - Adjust filename, context - Number DEVCONF enumerators explicitly to match upstream] Signed-off-by: Ben Hutchings --- Documentation/networking/ip-sysctl.txt | 8 ++++++++ include/linux/ipv6.h | 3 +++ net/ipv6/addrconf.c | 10 ++++++++++ net/ipv6/ndisc.c | 16 +++++++--------- 4 files changed, 28 insertions(+), 9 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 3b979c6ba84b..0df5824fee3b 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -1070,6 +1070,14 @@ accept_ra_defrtr - BOOLEAN Functional default: enabled if accept_ra is enabled. disabled if accept_ra is disabled. +accept_ra_min_hop_limit - INTEGER + Minimum hop limit Information in Router Advertisement. + + Hop limit Information in Router Advertisement less than this + variable shall be ignored. + + Default: 1 + accept_ra_pinfo - BOOLEAN Learn Prefix Information in Router Advertisement. diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h index 00ef00d0f315..2729d09e9c11 100644 --- a/include/linux/ipv6.h +++ b/include/linux/ipv6.h @@ -153,6 +153,7 @@ struct ipv6_devconf { #endif __s32 max_addresses; __s32 accept_ra_defrtr; + __s32 accept_ra_min_hop_limit; __s32 accept_ra_pinfo; #ifdef CONFIG_IPV6_ROUTER_PREF __s32 accept_ra_rtr_pref; @@ -213,6 +214,8 @@ enum { DEVCONF_DISABLE_IPV6, DEVCONF_ACCEPT_DAD, DEVCONF_FORCE_TLLAO, + DEVCONF_USE_OIF_ADDRS_ONLY = 37, + DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT, DEVCONF_MAX }; diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 006867df0178..79eceab4637a 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -185,6 +185,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = { #endif .max_addresses = IPV6_MAX_ADDRESSES, .accept_ra_defrtr = 1, + .accept_ra_min_hop_limit= 1, .accept_ra_pinfo = 1, #ifdef CONFIG_IPV6_ROUTER_PREF .accept_ra_rtr_pref = 1, @@ -219,6 +220,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = { #endif .max_addresses = IPV6_MAX_ADDRESSES, .accept_ra_defrtr = 1, + .accept_ra_min_hop_limit= 1, .accept_ra_pinfo = 1, #ifdef CONFIG_IPV6_ROUTER_PREF .accept_ra_rtr_pref = 1, @@ -3943,6 +3945,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf, #endif array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses; array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr; + array[DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT] = cnf->accept_ra_min_hop_limit; array[DEVCONF_ACCEPT_RA_PINFO] = cnf->accept_ra_pinfo; #ifdef CONFIG_IPV6_ROUTER_PREF array[DEVCONF_ACCEPT_RA_RTR_PREF] = cnf->accept_ra_rtr_pref; @@ -4545,6 +4548,13 @@ static struct addrconf_sysctl_table .mode = 0644, .proc_handler = proc_dointvec, }, + { + .procname = "accept_ra_min_hop_limit", + .data = &ipv6_devconf.accept_ra_min_hop_limit, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, { .procname = "accept_ra_pinfo", .data = &ipv6_devconf.accept_ra_pinfo, diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 39836dafa931..e5b0f9e0deaa 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1276,18 +1276,16 @@ static void ndisc_router_discovery(struct sk_buff *skb) if (rt) rt->rt6i_expires = jiffies + (HZ * lifetime); - if (ra_msg->icmph.icmp6_hop_limit) { - /* Only set hop_limit on the interface if it is higher than - * the current hop_limit. - */ - if (in6_dev->cnf.hop_limit < ra_msg->icmph.icmp6_hop_limit) { + if (in6_dev->cnf.accept_ra_min_hop_limit < 256 && + ra_msg->icmph.icmp6_hop_limit) { + if (in6_dev->cnf.accept_ra_min_hop_limit <= ra_msg->icmph.icmp6_hop_limit) { in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit; + if (rt) + dst_metric_set(&rt->dst, RTAX_HOPLIMIT, + ra_msg->icmph.icmp6_hop_limit); } else { - ND_PRINTK2(KERN_WARNING "RA: Got route advertisement with lower hop_limit than current\n"); + ND_PRINTK2(KERN_WARNING "RA: Got route advertisement with lower hop_limit than minimum\n"); } - if (rt) - dst_metric_set(&rt->dst, RTAX_HOPLIMIT, - ra_msg->icmph.icmp6_hop_limit); } skip_defrtr: -- 2.39.2