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 <liuhangbin@gmail.com>
Acked-by: YOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 071fb18dc57c868e99367f9d3872bc0e91401414..07fad3d2fc5684d107122eb12cce3ab5f6041b43 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1321,6 +1321,14 @@ accept_ra_from_local - BOOLEAN
           disabled if accept_ra_from_local is disabled
                on a specific interface.
 
+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 e4b4649833227b2e31ba78ccaa45a7822d55fe5f..01c25923675b405de4bba0306429c09974c97f65 100644 (file)
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -29,6 +29,7 @@ struct ipv6_devconf {
        __s32           max_desync_factor;
        __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;

diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 5efa54ae567ca933a15dc1210b5af2cb569951c6..80f3b74446a1a3e56704550138e816014537e60f 100644 (file)
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -171,6 +171,8 @@ enum {
        DEVCONF_USE_OPTIMISTIC,
        DEVCONF_ACCEPT_RA_MTU,
        DEVCONF_STABLE_SECRET,
+       DEVCONF_USE_OIF_ADDRS_ONLY,
+       DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
        DEVCONF_MAX
 };
 

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index f4795b0d6e6ef5aa3f8164e87f945cb096c9e9bd..28c4bc58f2cc7c39bd757d1ed33b14461ffb66cd 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -195,6 +195,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
        .max_addresses          = IPV6_MAX_ADDRESSES,
        .accept_ra_defrtr       = 1,
        .accept_ra_from_local   = 0,
+       .accept_ra_min_hop_limit= 1,
        .accept_ra_pinfo        = 1,
 #ifdef CONFIG_IPV6_ROUTER_PREF
        .accept_ra_rtr_pref     = 1,
@@ -236,6 +237,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
        .max_addresses          = IPV6_MAX_ADDRESSES,
        .accept_ra_defrtr       = 1,
        .accept_ra_from_local   = 0,
+       .accept_ra_min_hop_limit= 1,
        .accept_ra_pinfo        = 1,
 #ifdef CONFIG_IPV6_ROUTER_PREF
        .accept_ra_rtr_pref     = 1,
@@ -4565,6 +4567,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
        array[DEVCONF_MAX_DESYNC_FACTOR] = cnf->max_desync_factor;
        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;
@@ -5457,6 +5460,13 @@ 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 96f153c0846b7abcd9b1af995c49067efbe7064d..abb0bdda759a50d18232c7001ab8ad1e670097a6 100644 (file)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1225,18 +1225,16 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 
        if (rt)
                rt6_set_expires(rt, 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_PRINTK(2, warn, "RA: Got route advertisement with lower hop_limit than current\n");
+                       ND_PRINTK(2, warn, "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: