net-ipv6: add support for sockopt(SOL_IPV6, IPV6_FREEBIND)

So far we've been relying on sockopt(SOL_IP, IP_FREEBIND) being usable
even on IPv6 sockets.

However, it turns out it is perfectly reasonable to want to set freebind
on an AF_INET6 SOCK_RAW socket - but there is no way to set any SOL_IP
socket option on such a socket (they're all blindly errored out).

One use case for this is to allow spoofing src ip on a raw socket
via sendmsg cmsg.

Tested:
  built, and booted
  # python
  >>> import socket
  >>> SOL_IP = socket.SOL_IP
  >>> SOL_IPV6 = socket.IPPROTO_IPV6
  >>> IP_FREEBIND = 15
  >>> IPV6_FREEBIND = 78
  >>> s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, 0)
  >>> s.getsockopt(SOL_IP, IP_FREEBIND)
  0
  >>> s.getsockopt(SOL_IPV6, IPV6_FREEBIND)
  0
  >>> s.setsockopt(SOL_IPV6, IPV6_FREEBIND, 1)
  >>> s.getsockopt(SOL_IP, IP_FREEBIND)
  1
  >>> s.getsockopt(SOL_IPV6, IPV6_FREEBIND)
  1

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h
index 46444f8fbee4eed8c4aa223ee5ff3ef1be182765..4f8f3eb0699f2e0c58d15036a63fbeda21cde562 100644 (file)
--- a/include/uapi/linux/in6.h
+++ b/include/uapi/linux/in6.h
@@ -284,6 +284,7 @@ struct in6_flowlabel_req {
 #define IPV6_TRANSPARENT        75
 #define IPV6_UNICAST_IF         76
 #define IPV6_RECVFRAGSIZE      77
+#define IPV6_FREEBIND          78
 
 /*
  * Multicast Routing:

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index a5e466d4e09310ed99c391fea4bb6126d83fbb56..b9404feabd7857fe0873fbc4f346d281f3600807 100644 (file)
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -377,6 +377,14 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
                retv = 0;
                break;
 
+       case IPV6_FREEBIND:
+               if (optlen < sizeof(int))
+                       goto e_inval;
+               /* we also don't have a separate freebind bit for IPV6 */
+               inet_sk(sk)->freebind = valbool;
+               retv = 0;
+               break;
+
        case IPV6_RECVORIGDSTADDR:
                if (optlen < sizeof(int))
                        goto e_inval;
@@ -1214,6 +1222,10 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
                val = inet_sk(sk)->transparent;
                break;
 
+       case IPV6_FREEBIND:
+               val = inet_sk(sk)->freebind;
+               break;
+
        case IPV6_RECVORIGDSTADDR:
                val = np->rxopt.bits.rxorigdstaddr;
                break;