ipv6: icmp: allow flowlabel reflection in echo replies

Extend flowlabel_reflect bitmask to allow conditional
reflection of incoming flowlabels in echo replies.

Note this has precedence against auto flowlabels.

Add flowlabel_reflect enum to replace hard coded
values.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 17 insertions, 5 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index e0d8a96e2c67..f0e6d1f53485 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1452,7 +1452,7 @@ flowlabel_reflect - INTEGER
         environments. See RFC 7690 and:
         https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01
 
-        This is a mask of two bits.
+        This is a bitmask.
         1: enabled for established flows
 
         Note that this prevents automatic flowlabel changes, as done
@@ -1463,6 +1463,8 @@ flowlabel_reflect - INTEGER
         If set, a RST packet sent in response to a SYN packet on a closed
         port will reflect the incoming flow label.
 
+        4: enabled for ICMPv6 echo reply messages.
+
         Default: 0
 
 fib_multipath_hash_policy - INTEGER
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index b41f6a0fa903..8eca5fb30376 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -301,6 +301,13 @@ struct ipv6_txoptions {
         /* Option buffer, as read by IPV6_PKTOPTIONS, starts here. */
 };
 
+/* flowlabel_reflect sysctl values */
+enum flowlabel_reflect {
+        FLOWLABEL_REFLECT_ESTABLISHED           = 1,
+        FLOWLABEL_REFLECT_TCP_RESET             = 2,
+        FLOWLABEL_REFLECT_ICMPV6_ECHO_REPLIES   = 4,
+};
+
 struct ip6_flowlabel {
         struct ip6_flowlabel __rcu *next;
         __be32                  label;
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 7382a927d1eb..8369af32cef6 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -208,7 +208,7 @@ lookup_protocol:
         np->mc_loop     = 1;
         np->mc_all      = 1;
         np->pmtudisc    = IPV6_PMTUDISC_WANT;
-        np->repflow     = net->ipv6.sysctl.flowlabel_reflect & 1;
+        np->repflow     = net->ipv6.sysctl.flowlabel_reflect & FLOWLABEL_REFLECT_ESTABLISHED;
         sk->sk_ipv6only = net->ipv6.sysctl.bindv6only;
 
         /* Init the ipv4 part of the socket since we can have sockets
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 12906301ec7b..62c997201970 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -703,6 +703,9 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
         tmp_hdr.icmp6_type = ICMPV6_ECHO_REPLY;
 
         memset(&fl6, 0, sizeof(fl6));
+        if (net->ipv6.sysctl.flowlabel_reflect & FLOWLABEL_REFLECT_ICMPV6_ECHO_REPLIES)
+                fl6.flowlabel = ip6_flowlabel(ipv6_hdr(skb));
+
         fl6.flowi6_proto = IPPROTO_ICMPV6;
         fl6.daddr = ipv6_hdr(skb)->saddr;
         if (saddr)
diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
index 6d86fac472e7..8b3fe81783ed 100644
--- a/net/ipv6/sysctl_net_ipv6.c
+++ b/net/ipv6/sysctl_net_ipv6.c
@@ -23,7 +23,7 @@
 
 static int zero;
 static int one = 1;
-static int three = 3;
+static int flowlabel_reflect_max = 0x7;
 static int auto_flowlabels_min;
 static int auto_flowlabels_max = IP6_AUTO_FLOW_LABEL_MAX;
 
@@ -116,7 +116,7 @@ static struct ctl_table ipv6_table_template[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
                 .extra1         = &zero,
-                .extra2         = &three,
+                .extra2         = &flowlabel_reflect_max,
         },
         {
                 .procname       = "max_dst_opts_number",
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 408d9ec26971..4f3f99b39820 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -989,7 +989,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
                 if (sk->sk_state == TCP_TIME_WAIT)
                         label = cpu_to_be32(inet_twsk(sk)->tw_flowlabel);
         } else {
-                if (net->ipv6.sysctl.flowlabel_reflect & 2)
+                if (net->ipv6.sysctl.flowlabel_reflect & FLOWLABEL_REFLECT_TCP_RESET)
                         label = ip6_flowlabel(ipv6h);
         }