ipv4: New multicast-all socket option

After some discussion offline with Christoph Lameter and David Stevens
regarding multicast behaviour in Linux, I'm submitting a slightly
modified patch from the one Christoph submitted earlier.

This patch provides a new socket option IP_MULTICAST_ALL.

In this case, default behaviour is _unchanged_ from the current
Linux standard. The socket option is set by default to provide
original behaviour. Sockets wishing to receive data only from
multicast groups they join explicitly will need to clear this
socket option.

Signed-off-by: Nivedita Singhvi <niv@us.ibm.com>
Signed-off-by: Christoph Lameter<cl@linux.com>
Acked-by: David Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 21b0187123d..cb49936856e 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -453,6 +453,7 @@ static int do_ip_setsockopt(struct sock *sk, int level,
                              (1<<IP_ROUTER_ALERT) | (1<<IP_FREEBIND) |
                              (1<<IP_PASSSEC) | (1<<IP_TRANSPARENT))) ||
             optname == IP_MULTICAST_TTL ||
+            optname == IP_MULTICAST_ALL ||
             optname == IP_MULTICAST_LOOP ||
             optname == IP_RECVORIGDSTADDR) {
                 if (optlen >= sizeof(int)) {
@@ -898,6 +899,13 @@ mc_msf_out:
                 kfree(gsf);
                 break;
         }
+        case IP_MULTICAST_ALL:
+                if (optlen < 1)
+                        goto e_inval;
+                if (val != 0 && val != 1)
+                        goto e_inval;
+                inet->mc_all = val;
+                break;
         case IP_ROUTER_ALERT:
                 err = ip_ra_control(sk, val ? 1 : 0, NULL);
                 break;
@@ -1151,6 +1159,9 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
                 release_sock(sk);
                 return err;
         }
+        case IP_MULTICAST_ALL:
+                val = inet->mc_all;
+                break;
         case IP_PKTOPTIONS:
         {
                 struct msghdr msg;