net: ipv6: Add IPv6 support to the ping socket.

This adds the ability to send ICMPv6 echo requests without a
raw socket. The equivalent ability for ICMPv4 was added in
2011.

Instead of having separate code paths for IPv4 and IPv6, make
most of the code in net/ipv4/ping.c dual-stack and only add a
few IPv6-specific bits (like the protocol definition) to a new
net/ipv6/ping.c. Hopefully this will reduce divergence and/or
duplication of bugs in the future.

Caveats:

- Setting options via ancillary data (e.g., using IPV6_PKTINFO
  to specify the outgoing interface) is not yet supported.
- There are no separate security settings for IPv4 and IPv6;
  everything is controlled by /proc/net/ipv4/ping_group_range.
- The proc interface does not yet display IPv6 ping sockets
  properly.

Tested with a patched copy of ping6 and using raw socket calls.
Compiles and works with all of CONFIG_IPV6={n,m,y}.

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -260,6 +260,12 @@ static inline void fl6_sock_release(struct ip6_flowlabel *fl)
 
 extern void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info);
 
+int icmpv6_push_pending_frames(struct sock *sk, struct flowi6 *fl6,
+			       struct icmp6hdr *thdr, int len);
+
+struct dst_entry *icmpv6_route_lookup(struct net *net, struct sk_buff *skb,
+				      struct sock *sk, struct flowi6 *fl6);
+
 extern int 			ip6_ra_control(struct sock *sk, int sel);
 
 extern int			ipv6_parse_hopopts(struct sk_buff *skb);

include/net/ping.h

@@ -13,6 +13,7 @@
 #ifndef _PING_H
 #define _PING_H
 
+#include <net/icmp.h>
 #include <net/netns/hash.h>
 
 /* PING_HTABLE_SIZE must be power of 2 */
@@ -28,6 +29,18 @@
  */
 #define GID_T_MAX (((gid_t)~0U) >> 1)
 
+/* Compatibility glue so we can support IPv6 when it's compiled as a module */
+struct pingv6_ops {
+	int (*ipv6_recv_error)(struct sock *sk, struct msghdr *msg, int len);
+	int (*ip6_datagram_recv_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);
+	int (*ipv6_chk_addr)(struct net *net, const struct in6_addr *addr,
+			     struct net_device *dev, int strict);
+};
+
 struct ping_table {
 	struct hlist_nulls_head	hash[PING_HTABLE_SIZE];
 	rwlock_t		lock;
@@ -39,17 +52,47 @@ struct ping_iter_state {
 };
 
 extern struct proto ping_prot;
+extern struct ping_table ping_table;
+#if IS_ENABLED(CONFIG_IPV6)
+extern struct pingv6_ops pingv6_ops;
+#endif
 
+struct pingfakehdr {
+	struct icmphdr icmph;
+	struct iovec *iov;
+	sa_family_t family;
+	__wsum wcheck;
+};
 
-extern void ping_rcv(struct sk_buff *);
-extern void ping_err(struct sk_buff *, u32 info);
+int  ping_get_port(struct sock *sk, unsigned short ident);
+void ping_hash(struct sock *sk);
+void ping_unhash(struct sock *sk);
+
+int  ping_init_sock(struct sock *sk);
+void ping_close(struct sock *sk, long timeout);
+int  ping_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len);
+void ping_err(struct sk_buff *skb, int offset, u32 info);
+int  ping_getfrag(void *from, char *to, int offset, int fraglen, int odd,
+		  struct sk_buff *);
+
+int  ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
+		  size_t len, int noblock, int flags, int *addr_len);
+int  ping_common_sendmsg(int family, struct msghdr *msg, size_t len,
+			 void *user_icmph, size_t icmph_len);
+int  ping_v4_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
+		     size_t len);
+int  ping_v6_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
+		     size_t len);
+int  ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
+void ping_rcv(struct sk_buff *skb);
 
 #ifdef CONFIG_PROC_FS
 extern int __init ping_proc_init(void);
 extern void ping_proc_exit(void);
 #endif
 
 void __init ping_init(void);
-
+int  __init pingv6_init(void);
+void pingv6_exit(void);
 
 #endif /* _PING_H */

include/net/transp_v6.h

@@ -11,6 +11,7 @@ extern struct proto rawv6_prot;
 extern struct proto udpv6_prot;
 extern struct proto udplitev6_prot;
 extern struct proto tcpv6_prot;
+extern struct proto pingv6_prot;
 
 struct flowi6;
 
@@ -21,6 +22,8 @@ extern int				ipv6_frag_init(void);
 extern void				ipv6_frag_exit(void);
 
 /* transport protocols */
+extern int				pingv6_init(void);
+extern void				pingv6_exit(void);
 extern int				rawv6_init(void);
 extern void				rawv6_exit(void);
 extern int				udpv6_init(void);

net/ipv4/icmp.c

@@ -939,7 +939,8 @@ int icmp_rcv(struct sk_buff *skb)
 void icmp_err(struct sk_buff *skb, u32 info)
 {
 	struct iphdr *iph = (struct iphdr *)skb->data;
-	struct icmphdr *icmph = (struct icmphdr *)(skb->data+(iph->ihl<<2));
+	int offset = iph->ihl<<2;
+	struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
 	int type = icmp_hdr(skb)->type;
 	int code = icmp_hdr(skb)->code;
 	struct net *net = dev_net(skb->dev);
@@ -949,7 +950,7 @@ void icmp_err(struct sk_buff *skb, u32 info)
 	 * triggered by ICMP_ECHOREPLY which sent from kernel.
 	 */
 	if (icmph->type != ICMP_ECHOREPLY) {
-		ping_err(skb, info);
+		ping_err(skb, offset, info);
 		return;
 	}