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>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 1084304..2faef33 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -284,6 +284,8 @@
 
 #define __ipv6_only_sock(sk)	(inet6_sk(sk)->ipv6only)
 #define ipv6_only_sock(sk)	((sk)->sk_family == PF_INET6 && __ipv6_only_sock(sk))
+#define ipv6_sk_rxinfo(sk)	((sk)->sk_family == PF_INET6 && \
+				 inet6_sk(sk)->rxopt.bits.rxinfo)
 
 static inline const struct in6_addr *inet6_rcv_saddr(const struct sock *sk)
 {
@@ -300,6 +302,7 @@
 #else
 #define __ipv6_only_sock(sk)	0
 #define ipv6_only_sock(sk)	0
+#define ipv6_sk_rxinfo(sk)	0
 
 static inline struct ipv6_pinfo * inet6_sk(const struct sock *__sk)
 {
diff --git a/include/net/ip.h b/include/net/ip.h
index 7876e3b..23be0fd 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -63,6 +63,7 @@
 };
 
 #define IPCB(skb) ((struct inet_skb_parm*)((skb)->cb))
+#define PKTINFO_SKB_CB(skb) ((struct in_pktinfo *)((skb)->cb))
 
 struct ip_ra_chain {
 	struct ip_ra_chain __rcu *next;
diff --git a/include/net/ping.h b/include/net/ping.h
index 7601365..026479b 100644
--- a/include/net/ping.h
+++ b/include/net/ping.h
@@ -33,8 +33,12 @@
 struct pingv6_ops {
 	int (*ipv6_recv_error)(struct sock *sk, struct msghdr *msg, int len,
 			       int *addr_len);
-	int (*ip6_datagram_recv_ctl)(struct sock *sk, struct msghdr *msg,
-				     struct sk_buff *skb);
+	void (*ip6_datagram_recv_common_ctl)(struct sock *sk,
+					     struct msghdr *msg,
+					     struct sk_buff *skb);
+	void (*ip6_datagram_recv_specific_ctl)(struct sock *sk,
+					       struct msghdr *msg,
+					       struct sk_buff *skb);
 	int (*icmpv6_err_convert)(u8 type, u8 code, int *err);
 	void (*ipv6_icmp_error)(struct sock *sk, struct sk_buff *skb, int err,
 				__be16 port, u32 info, u8 *payload);
diff --git a/include/net/transp_v6.h b/include/net/transp_v6.h
index 48660e5..b927413d 100644
--- a/include/net/transp_v6.h
+++ b/include/net/transp_v6.h
@@ -32,8 +32,13 @@
 
 int udpv6_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
 
-int ip6_datagram_recv_ctl(struct sock *sk, struct msghdr *msg,
-			  struct sk_buff *skb);
+/* this does all the common and the specific ctl work */
+void ip6_datagram_recv_ctl(struct sock *sk, struct msghdr *msg,
+			   struct sk_buff *skb);
+void ip6_datagram_recv_common_ctl(struct sock *sk, struct msghdr *msg,
+				  struct sk_buff *skb);
+void ip6_datagram_recv_specific_ctl(struct sock *sk, struct msghdr *msg,
+				    struct sk_buff *skb);
 
 int ip6_datagram_send_ctl(struct net *net, struct sock *sk, struct msghdr *msg,
 			  struct flowi6 *fl6, struct ipv6_txoptions *opt,