5 files changed, 26 insertions, 1 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index d71afa8bd828..7373115407e4 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1094,6 +1094,13 @@ bindv6only - BOOLEAN
 
         Default: FALSE (as specified in RFC3493)
 
+anycast_src_echo_reply - BOOLEAN
+        Controls the use of anycast addresses as source addresses for ICMPv6
+        echo reply
+        TRUE:  enabled
+        FALSE: disabled
+        Default: FALSE
+
 IPv6 Fragmentation:
 
 ip6frag_high_thresh - INTEGER
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 1fb6cddbd448..017badb1aec7 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -152,6 +152,13 @@ static inline bool ipv6_unicast_destination(const struct sk_buff *skb)
         return rt->rt6i_flags & RTF_LOCAL;
 }
 
+static inline bool ipv6_anycast_destination(const struct sk_buff *skb)
+{
+        struct rt6_info *rt = (struct rt6_info *) skb_dst(skb);
+
+        return rt->rt6i_flags & RTF_ANYCAST;
+}
+
 int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
 
 static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 0fb2401197c5..76fc7d1dbfd3 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -73,6 +73,7 @@ struct netns_ipv6 {
 #endif
         atomic_t                dev_addr_genid;
         atomic_t                rt_genid;
+        int                     anycast_src_echo_reply;
 };
 
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 5d420095190f..9a809a4b3d86 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -556,7 +556,9 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 
         saddr = &ipv6_hdr(skb)->daddr;
 
-        if (!ipv6_unicast_destination(skb))
+        if (!ipv6_unicast_destination(skb) &&
+            !(net->ipv6.anycast_src_echo_reply &&
+              ipv6_anycast_destination(skb)))
                 saddr = NULL;
 
         memcpy(&tmp_hdr, icmph, sizeof(tmp_hdr));
diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
index 107b2f1d90ae..6b6a2c83027e 100644
--- a/net/ipv6/sysctl_net_ipv6.c
+++ b/net/ipv6/sysctl_net_ipv6.c
@@ -24,6 +24,13 @@ static struct ctl_table ipv6_table_template[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec
         },
+        {
+                .procname       = "anycast_src_echo_reply",
+                .data           = &init_net.ipv6.anycast_src_echo_reply,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec
+        },
         { }
 };
 
@@ -51,6 +58,7 @@ static int __net_init ipv6_sysctl_net_init(struct net *net)
         if (!ipv6_table)
                 goto out;
         ipv6_table[0].data = &net->ipv6.sysctl.bindv6only;
+        ipv6_table[1].data = &net->ipv6.anycast_src_echo_reply;
 
         ipv6_route_table = ipv6_route_sysctl_init(net);
         if (!ipv6_route_table)