net: ipv6: Add a sysctl to make optimistic addresses useful candidates

Add a sysctl that causes an interface's optimistic addresses
to be considered equivalent to other non-deprecated addresses
for source address selection purposes.  Preferred addresses
will still take precedence over optimistic addresses, subject
to other ranking in the source address selection algorithm.

This is useful where different interfaces are connected to
different networks from different ISPs (e.g., a cell network
and a home wifi network).

The current behaviour complies with RFC 3484/6724, and it
makes sense if the host has only one interface, or has
multiple interfaces on the same network (same or cooperating
administrative domain(s), but not in the multiple distinct
networks case.

For example, if a mobile device has an IPv6 address on an LTE
network and then connects to IPv6-enabled wifi, while the wifi
IPv6 address is undergoing DAD, IPv6 connections will try use
the wifi default route with the LTE IPv6 address, and will get
stuck until they time out.

Also, because optimistic nodes can receive frames, issue
an RTM_NEWADDR as soon as DAD starts (with the IFA_F_OPTIMSTIC
flag appropriately set).  A second RTM_NEWADDR is sent if DAD
completes (the address flags have changed), otherwise an
RTM_DELADDR is sent.

Also: add an entry in ip-sysctl.txt for optimistic_dad.

[cherry-pick of net-next 7fd2561e4ebdd070ebba6d3326c4c5b13942323f]

Signed-off-by: Erik Kline <ek@google.com>
Acked-by: Lorenzo Colitti <lorenzo@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Bug: 17769720
Change-Id: Ic7e50781c607e1f3a492d9ce7395946efb95c533

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 6e5c7c7333bdb3aa73a84a2509670f289abc958b..74b49ba13b1fc269bf637dcae0264871bf583b32 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1333,6 +1333,19 @@ ndisc_notify - BOOLEAN
        1 - Generate unsolicited neighbour advertisements when device is brought
            up or hardware address changes.
 
+optimistic_dad - BOOLEAN
+       Whether to perform Optimistic Duplicate Address Detection (RFC 4429).
+               0: disabled (default)
+               1: enabled
+
+use_optimistic - BOOLEAN
+       If enabled, do not classify optimistic addresses as deprecated during
+       source address selection.  Preferred addresses will still be chosen
+       before optimistic addresses, subject to other ranking in the source
+       address selection algorithm.
+               0: disabled (default)
+               1: enabled
+
 icmp/*:
 ratelimit - INTEGER
        Limit the maximal rates for sending ICMPv6 packets.

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 867833ba6bd166dbfcc4e1259b6dfbcdd00d0650..76b5114e9d82ac8809ff58e163e9df5165d1ebe6 100644 (file)
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -41,6 +41,7 @@ struct ipv6_devconf {
        __s32           accept_source_route;
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        __s32           optimistic_dad;
+       __s32           use_optimistic;
 #endif
 #ifdef CONFIG_IPV6_MROUTE
        __s32           mc_forwarding;

diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 4214fac1bf4fbeea0c702c440f39aaa6cad94291..e9d0f7efde3b8dbd41790360df37336e213c1531 100644 (file)
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -161,6 +161,7 @@ enum {
        DEVCONF_FORCE_TLLAO,
        DEVCONF_NDISC_NOTIFY,
        DEVCONF_ACCEPT_RA_RT_TABLE,
+       DEVCONF_USE_OPTIMISTIC,
        DEVCONF_MAX
 };
 

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index cec8cb4d292db398f3d7cdd8d420f0cb3333be37..e1381119a6d8412b955498dff3ddb593e8342d5a 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1174,6 +1174,9 @@ enum {
 #endif
        IPV6_SADDR_RULE_ORCHID,
        IPV6_SADDR_RULE_PREFIX,
+#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
+       IPV6_SADDR_RULE_NOT_OPTIMISTIC,
+#endif
        IPV6_SADDR_RULE_MAX
 };
 
@@ -1201,6 +1204,15 @@ static inline int ipv6_saddr_preferred(int type)
        return 0;
 }
 
+static inline bool ipv6_use_optimistic_addr(struct inet6_dev *idev)
+{
+#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
+       return idev && idev->cnf.optimistic_dad && idev->cnf.use_optimistic;
+#else
+       return false;
+#endif
+}
+
 static int ipv6_get_saddr_eval(struct net *net,
                               struct ipv6_saddr_score *score,
                               struct ipv6_saddr_dst *dst,
@@ -1261,10 +1273,16 @@ static int ipv6_get_saddr_eval(struct net *net,
                score->scopedist = ret;
                break;
        case IPV6_SADDR_RULE_PREFERRED:
+           {
                /* Rule 3: Avoid deprecated and optimistic addresses */
+               u8 avoid = IFA_F_DEPRECATED;
+
+               if (!ipv6_use_optimistic_addr(score->ifa->idev))
+                       avoid |= IFA_F_OPTIMISTIC;
                ret = ipv6_saddr_preferred(score->addr_type) ||
-                     !(score->ifa->flags & (IFA_F_DEPRECATED|IFA_F_OPTIMISTIC));
+                     !(score->ifa->flags & avoid);
                break;
+           }
 #ifdef CONFIG_IPV6_MIP6
        case IPV6_SADDR_RULE_HOA:
            {
@@ -1312,6 +1330,14 @@ static int ipv6_get_saddr_eval(struct net *net,
                        ret = score->ifa->prefix_len;
                score->matchlen = ret;
                break;
+#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
+       case IPV6_SADDR_RULE_NOT_OPTIMISTIC:
+               /* Optimistic addresses still have lower precedence than other
+                * preferred addresses.
+                */
+               ret = !(score->ifa->flags & IFA_F_OPTIMISTIC);
+               break;
+#endif
        default:
                ret = 0;
        }
@@ -3245,8 +3271,15 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp)
         * Optimistic nodes can start receiving
         * Frames right away
         */
-       if (ifp->flags & IFA_F_OPTIMISTIC)
+       if (ifp->flags & IFA_F_OPTIMISTIC) {
                ip6_ins_rt(ifp->rt);
+               if (ipv6_use_optimistic_addr(idev)) {
+                       /* Because optimistic nodes can use this address,
+                        * notify listeners. If DAD fails, RTM_DELADDR is sent.
+                        */
+                       ipv6_ifa_notify(RTM_NEWADDR, ifp);
+               }
+       }
 
        addrconf_dad_kick(ifp);
 out:
@@ -4192,6 +4225,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
        array[DEVCONF_ACCEPT_SOURCE_ROUTE] = cnf->accept_source_route;
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        array[DEVCONF_OPTIMISTIC_DAD] = cnf->optimistic_dad;
+       array[DEVCONF_USE_OPTIMISTIC] = cnf->use_optimistic;
 #endif
 #ifdef CONFIG_IPV6_MROUTE
        array[DEVCONF_MC_FORWARDING] = cnf->mc_forwarding;
@@ -4926,6 +4960,14 @@ static struct addrconf_sysctl_table
                        .proc_handler   = proc_dointvec,
 
                },
+               {
+                       .procname       = "use_optimistic",
+                       .data           = &ipv6_devconf.use_optimistic,
+                       .maxlen         = sizeof(int),
+                       .mode           = 0644,
+                       .proc_handler   = proc_dointvec,
+
+               },
 #endif
 #ifdef CONFIG_IPV6_MROUTE
                {