ipv6: Nonlocal bind

Add support to allow non-local binds similar to how this was done for IPv4.
Non-local binds are very useful in emulating the Internet in a box, etc.

This add the ip_nonlocal_bind sysctl under ipv6.

Testing:

Set up nonlocal binding and receive routing on a host, e.g.:

ip -6 rule add from ::/0 iif eth0 lookup 200
ip -6 route add local 2001:0:0:1::/64 dev lo proto kernel scope host table 200
sysctl -w net.ipv6.ip_nonlocal_bind=1

Set up routing to 2001:0:0:1::/64 on peer to go to first host

ping6 -I 2001:0:0:1::1 peer-address -- to verify

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 20 insertions, 3 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 5fae7704daab..f63aeefd2c24 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1435,6 +1435,11 @@ mtu - INTEGER
         Default Maximum Transfer Unit
         Default: 1280 (IPv6 required minimum)
 
+ip_nonlocal_bind - BOOLEAN
+        If set, allows processes to bind() to non-local IPv6 addresses,
+        which can be quite useful - but may break some applications.
+        Default: 0
+
 router_probe_interval - INTEGER
         Minimum interval (in seconds) between Router Probing described
         in RFC4191.
diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 8d93544a2d2b..c0368db6df54 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -31,6 +31,7 @@ struct netns_sysctl_ipv6 {
         int auto_flowlabels;
         int icmpv6_time;
         int anycast_src_echo_reply;
+        int ip_nonlocal_bind;
         int fwmark_reflect;
         int idgen_retries;
         int idgen_delay;
diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 05ff44b758df..e89094ab5ddb 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -363,7 +363,8 @@ static int ping_check_bind_addr(struct sock *sk, struct inet_sock *isk,
                                                     scoped);
                 rcu_read_unlock();
 
-                if (!(isk->freebind || isk->transparent || has_addr ||
+                if (!(net->ipv6.sysctl.ip_nonlocal_bind ||
+                      isk->freebind || isk->transparent || has_addr ||
                       addr_type == IPV6_ADDR_ANY))
                         return -EADDRNOTAVAIL;
 
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 39e670a91596..7bc92ea4ae8f 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -342,7 +342,8 @@ int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
                          */
                         v4addr = LOOPBACK4_IPV6;
                         if (!(addr_type & IPV6_ADDR_MULTICAST)) {
-                                if (!(inet->freebind || inet->transparent) &&
+                                if (!net->ipv6.sysctl.ip_nonlocal_bind &&
+                                    !(inet->freebind || inet->transparent) &&
                                     !ipv6_chk_addr(net, &addr->sin6_addr,
                                                    dev, 0)) {
                                         err = -EADDRNOTAVAIL;
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index ca4700cb26c4..fdbada1569a3 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -295,7 +295,8 @@ static int rawv6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
                  * unspecified and mapped address have a v4 equivalent.
                  */
                 v4addr = LOOPBACK4_IPV6;
-                if (!(addr_type & IPV6_ADDR_MULTICAST)) {
+                if (!(addr_type & IPV6_ADDR_MULTICAST) &&
+                    !sock_net(sk)->ipv6.sysctl.ip_nonlocal_bind) {
                         err = -EADDRNOTAVAIL;
                         if (!ipv6_chk_addr(sock_net(sk), &addr->sin6_addr,
                                            dev, 0)) {
diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
index 4e705add4f18..db48aebd9c47 100644
--- a/net/ipv6/sysctl_net_ipv6.c
+++ b/net/ipv6/sysctl_net_ipv6.c
@@ -75,6 +75,13 @@ static struct ctl_table ipv6_table_template[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec
         },
+        {
+                .procname       = "ip_nonlocal_bind",
+                .data           = &init_net.ipv6.sysctl.ip_nonlocal_bind,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec
+        },
         { }
 };
 
@@ -117,6 +124,7 @@ static int __net_init ipv6_sysctl_net_init(struct net *net)
         ipv6_table[5].data = &net->ipv6.sysctl.idgen_retries;
         ipv6_table[6].data = &net->ipv6.sysctl.idgen_delay;
         ipv6_table[7].data = &net->ipv6.sysctl.flowlabel_state_ranges;
+        ipv6_table[8].data = &net->ipv6.sysctl.ip_nonlocal_bind;
 
         ipv6_route_table = ipv6_route_sysctl_init(net);
         if (!ipv6_route_table)