icmp6: support rfc 4884

Extend the rfc 4884 read interface introduced for ipv4 in
commit eba75c58 ("icmp: support rfc 4884") to ipv6.

Add socket option SOL_IPV6/IPV6_RECVERR_RFC4884.

Changes v1->v2:
  - make ipv6_icmp_error_rfc4884 static (file scope)
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -283,6 +283,7 @@ struct ipv6_pinfo {
 				autoflowlabel:1,
 				autoflowlabel_set:1,
 				mc_all:1,
+				recverr_rfc4884:1,
 				rtalert_isolate:1;
 	__u8			min_hopcount;
 	__u8			tclass;

include/uapi/linux/icmpv6.h

@@ -68,6 +68,7 @@ struct icmp6hdr {
 #define icmp6_mtu		icmp6_dataun.un_data32[0]
 #define icmp6_unused		icmp6_dataun.un_data32[0]
 #define icmp6_maxdelay		icmp6_dataun.un_data16[0]
+#define icmp6_datagram_len	icmp6_dataun.un_data8[0]
 #define icmp6_router		icmp6_dataun.u_nd_advt.router
 #define icmp6_solicited		icmp6_dataun.u_nd_advt.solicited
 #define icmp6_override		icmp6_dataun.u_nd_advt.override

include/uapi/linux/in6.h

@@ -179,6 +179,7 @@ struct in6_flowlabel_req {
 #define IPV6_LEAVE_ANYCAST	28
 #define IPV6_MULTICAST_ALL	29
 #define IPV6_ROUTER_ALERT_ISOLATE	30
+#define IPV6_RECVERR_RFC4884	31
 
 /* IPV6_MTU_DISCOVER values */
 #define IPV6_PMTUDISC_DONT		0

net/ipv4/icmp.c

@@ -1173,6 +1173,7 @@ void ip_icmp_error_rfc4884(const struct sk_buff *skb,
 	if (!ip_icmp_error_rfc4884_validate(skb, off))
 		out->flags |= SO_EE_RFC4884_FLAG_INVALID;
 }
+EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
 
 int icmp_err(struct sk_buff *skb, u32 info)
 {

net/ipv6/datagram.c

@@ -19,6 +19,7 @@
 #include <linux/route.h>
 #include <linux/slab.h>
 #include <linux/export.h>
+#include <linux/icmp.h>
 
 #include <net/ipv6.h>
 #include <net/ndisc.h>
@@ -284,6 +285,17 @@ int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *uaddr,
 }
 EXPORT_SYMBOL_GPL(ip6_datagram_connect_v6_only);
 
+static void ipv6_icmp_error_rfc4884(const struct sk_buff *skb,
+				    struct sock_ee_data_rfc4884 *out)
+{
+	switch (icmp6_hdr(skb)->icmp6_type) {
+	case ICMPV6_TIME_EXCEED:
+	case ICMPV6_DEST_UNREACH:
+		ip_icmp_error_rfc4884(skb, out, sizeof(struct icmp6hdr),
+				      icmp6_hdr(skb)->icmp6_datagram_len * 8);
+	}
+}
+
 void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 		     __be16 port, u32 info, u8 *payload)
 {
@@ -313,6 +325,10 @@ void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 	serr->port = port;
 
 	__skb_pull(skb, payload - skb->data);
+
+	if (inet6_sk(sk)->recverr_rfc4884)
+		ipv6_icmp_error_rfc4884(skb, &serr->ee.ee_rfc4884);
+
 	skb_reset_transport_header(skb);
 
 	if (sock_queue_err_skb(sk, skb))

net/ipv6/ipv6_sockglue.c

@@ -965,6 +965,14 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		np->rxopt.bits.recvfragsize = valbool;
 		retv = 0;
 		break;
+	case IPV6_RECVERR_RFC4884:
+		if (optlen < sizeof(int))
+			goto e_inval;
+		if (val < 0 || val > 1)
+			goto e_inval;
+		np->recverr_rfc4884 = valbool;
+		retv = 0;
+		break;
 	}
 
 	release_sock(sk);
@@ -1439,6 +1447,10 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		val = np->rtalert_isolate;
 		break;
 
+	case IPV6_RECVERR_RFC4884:
+		val = np->recverr_rfc4884;
+		break;
+
 	default:
 		return -ENOPROTOOPT;
 	}