3 files changed, 53 insertions, 23 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 31d8c71986b4..5cd99271d3a6 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -432,17 +432,32 @@ void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 port, u32 inf
 		kfree_skb(skb);
 }
 
-static bool ipv4_pktinfo_prepare_errqueue(const struct sock *sk,
-					  const struct sk_buff *skb,
-					  int ee_origin)
+/* IPv4 supports cmsg on all imcp errors and some timestamps
+ *
+ * Timestamp code paths do not initialize the fields expected by cmsg:
+ * the PKTINFO fields in skb->cb[]. Fill those in here.
+ */
+static bool ipv4_datagram_support_cmsg(const struct sock *sk,
+				       struct sk_buff *skb,
+				       int ee_origin)
 {
-	struct in_pktinfo *info = PKTINFO_SKB_CB(skb);
+	struct in_pktinfo *info;
+
+	if (ee_origin == SO_EE_ORIGIN_ICMP)
+		return true;
 
-	if ((ee_origin != SO_EE_ORIGIN_TIMESTAMPING) ||
-	    (!(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_CMSG)) ||
+	if (ee_origin == SO_EE_ORIGIN_LOCAL)
+		return false;
+
+	/* Support IP_PKTINFO on tstamp packets if requested, to correlate
+	 * timestamp with egress dev. Not possible for packets without dev
+	 * or without payload (SOF_TIMESTAMPING_OPT_TSONLY).
+	 */
+	if ((!(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_CMSG)) ||
 	    (!skb->dev))
 		return false;
 
+	info = PKTINFO_SKB_CB(skb);
 	info->ipi_spec_dst.s_addr = ip_hdr(skb)->saddr;
 	info->ipi_ifindex = skb->dev->ifindex;
 	return true;
@@ -483,7 +498,7 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 
 	serr = SKB_EXT_ERR(skb);
 
-	if (sin && skb->len) {
+	if (sin && serr->port) {
 		sin->sin_family = AF_INET;
 		sin->sin_addr.s_addr = *(__be32 *)(skb_network_header(skb) +
 						   serr->addr_offset);
@@ -496,9 +511,7 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 	sin = &errhdr.offender;
 	memset(sin, 0, sizeof(*sin));
 
-	if (skb->len &&
-	    (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
-	     ipv4_pktinfo_prepare_errqueue(sk, skb, serr->ee.ee_origin))) {
+	if (ipv4_datagram_support_cmsg(sk, skb, serr->ee.ee_origin)) {
 		sin->sin_family = AF_INET;
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
 		if (inet_sk(sk)->cmsg_flags)
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index c215be70cac0..ace8daca5c83 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -325,14 +325,34 @@ void ipv6_local_rxpmtu(struct sock *sk, struct flowi6 *fl6, u32 mtu)
 	kfree_skb(skb);
 }
 
-static void ip6_datagram_prepare_pktinfo_errqueue(struct sk_buff *skb)
+/* IPv6 supports cmsg on all origins aside from SO_EE_ORIGIN_LOCAL.
+ *
+ * At one point, excluding local errors was a quick test to identify icmp/icmp6
+ * errors. This is no longer true, but the test remained, so the v6 stack,
+ * unlike v4, also honors cmsg requests on all wifi and timestamp errors.
+ *
+ * Timestamp code paths do not initialize the fields expected by cmsg:
+ * the PKTINFO fields in skb->cb[]. Fill those in here.
+ */
+static bool ip6_datagram_support_cmsg(struct sk_buff *skb,
+				      struct sock_exterr_skb *serr)
 {
-	int ifindex = skb->dev ? skb->dev->ifindex : -1;
+	if (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
+	    serr->ee.ee_origin == SO_EE_ORIGIN_ICMP6)
+		return true;
+
+	if (serr->ee.ee_origin == SO_EE_ORIGIN_LOCAL)
+		return false;
+
+	if (!skb->dev)
+		return false;
 
 	if (skb->protocol == htons(ETH_P_IPV6))
-		IP6CB(skb)->iif = ifindex;
+		IP6CB(skb)->iif = skb->dev->ifindex;
 	else
-		PKTINFO_SKB_CB(skb)->ipi_ifindex = ifindex;
+		PKTINFO_SKB_CB(skb)->ipi_ifindex = skb->dev->ifindex;
+
+	return true;
 }
 
 /*
@@ -369,7 +389,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 
 	serr = SKB_EXT_ERR(skb);
 
-	if (sin && skb->len) {
+	if (sin && serr->port) {
 		const unsigned char *nh = skb_network_header(skb);
 		sin->sin6_family = AF_INET6;
 		sin->sin6_flowinfo = 0;
@@ -394,14 +414,11 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));
 	sin = &errhdr.offender;
 	memset(sin, 0, sizeof(*sin));
-	if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL && skb->len) {
+
+	if (ip6_datagram_support_cmsg(skb, serr)) {
 		sin->sin6_family = AF_INET6;
-		if (np->rxopt.all) {
-			if (serr->ee.ee_origin != SO_EE_ORIGIN_ICMP &&
-			    serr->ee.ee_origin != SO_EE_ORIGIN_ICMP6)
-				ip6_datagram_prepare_pktinfo_errqueue(skb);
+		if (np->rxopt.all)
 			ip6_datagram_recv_common_ctl(sk, msg, skb);
-		}
 		if (skb->protocol == htons(ETH_P_IPV6)) {
 			sin->sin6_addr = ipv6_hdr(skb)->saddr;
 			if (np->rxopt.all)
diff --git a/net/rxrpc/ar-error.c b/net/rxrpc/ar-error.c
index 5394b6be46ec..0610efa83d72 100644
--- a/net/rxrpc/ar-error.c
+++ b/net/rxrpc/ar-error.c
@@ -42,7 +42,8 @@ void rxrpc_UDP_error_report(struct sock *sk)
 		_leave("UDP socket errqueue empty");
 		return;
 	}
-	if (!skb->len) {
+	serr = SKB_EXT_ERR(skb);
+	if (!skb->len && serr->ee.ee_origin == SO_EE_ORIGIN_TIMESTAMPING) {
 		_leave("UDP empty message");
 		kfree_skb(skb);
 		return;
@@ -50,7 +51,6 @@ void rxrpc_UDP_error_report(struct sock *sk)
 
 	rxrpc_new_skb(skb);
 
-	serr = SKB_EXT_ERR(skb);
 	addr = *(__be32 *)(skb_network_header(skb) + serr->addr_offset);
 	port = serr->port;