ipv6: make IPV6_RECVPKTINFO work for ipv4 datagrams

We currently don't report IPV6_RECVPKTINFO in cmsg access ancillary data
for IPv4 datagrams on IPv6 sockets.

This patch splits the ip6_datagram_recv_ctl into two functions, one
which handles both protocol families, AF_INET and AF_INET6, while the
ip6_datagram_recv_specific_ctl only handles IPv6 cmsg data.

ip6_datagram_recv_*_ctl never reported back any errors, so we can make
them return void. Also provide a helper for protocols which don't offer dual
personality to further use ip6_datagram_recv_ctl, which is exported to
modules.

I needed to shuffle the code for ping around a bit to make it easier to
implement dual personality for ping ipv6 sockets in future.

Reported-by: Gert Doering <gert@space.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 9 insertions, 4 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 22f15eb1c260..580dd96666e0 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -56,7 +56,6 @@
 /*
  *      SOL_IP control messages.
  */
-#define PKTINFO_SKB_CB(__skb) ((struct in_pktinfo *)((__skb)->cb))
 
 static void ip_cmsg_recv_pktinfo(struct msghdr *msg, struct sk_buff *skb)
 {
@@ -1055,9 +1054,10 @@ e_inval:
 void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb)
 {
         struct in_pktinfo *pktinfo = PKTINFO_SKB_CB(skb);
+        bool prepare = (inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO) ||
+                       ipv6_sk_rxinfo(sk);
 
-        if ((inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO) &&
-            skb_rtable(skb)) {
+        if (prepare && skb_rtable(skb)) {
                 pktinfo->ipi_ifindex = inet_iif(skb);
                 pktinfo->ipi_spec_dst.s_addr = fib_compute_spec_dst(skb);
         } else {
diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index e09e8839d622..4a9e4266a0c3 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -906,7 +906,12 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                 }
 
                 if (inet6_sk(sk)->rxopt.all)
-                        pingv6_ops.ip6_datagram_recv_ctl(sk, msg, skb);
+                        pingv6_ops.ip6_datagram_recv_common_ctl(sk, msg, skb);
+                if (skb->protocol == htons(ETH_P_IPV6) &&
+                    inet6_sk(sk)->rxopt.all)
+                        pingv6_ops.ip6_datagram_recv_specific_ctl(sk, msg, skb);
+                else if (skb->protocol == htons(ETH_P_IP) && isk->cmsg_flags)
+                        ip_cmsg_recv(msg, skb);
 #endif
         } else {
                 BUG();