net: Get rcv tstamp if needed in nfnetlink_{log, queue}.c

If skb has the (rcv) timestamp available, nfnetlink_{log, queue}.c
logs/outputs it to the userspace.  When the locally generated skb is
looping from egress to ingress over a virtual interface (e.g. veth,
loopback...),  skb->tstamp may have the delivery time before it is
known that will be delivered locally and received by another sk.  Like
handling the delivery time in network tapping,  use ktime_get_real() to
get the (rcv) timestamp.  The earlier added helper skb_tstamp_cond() is
used to do this.  false is passed to the second 'cond' arg such
that doing ktime_get_real() or not only depends on the
netstamp_needed_key static key.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nfnetlink_log.c

@@ -460,6 +460,7 @@ __build_packet_message(struct nfnl_log_net *log,
 	sk_buff_data_t old_tail = inst->skb->tail;
 	struct sock *sk;
 	const unsigned char *hwhdrp;
+	ktime_t tstamp;
 
 	nlh = nfnl_msg_put(inst->skb, 0, 0,
 			   nfnl_msg_type(NFNL_SUBSYS_ULOG, NFULNL_MSG_PACKET),
@@ -588,9 +589,10 @@ __build_packet_message(struct nfnl_log_net *log,
 			goto nla_put_failure;
 	}
 
-	if (hooknum <= NF_INET_FORWARD && skb->tstamp) {
+	tstamp = skb_tstamp_cond(skb, false);
+	if (hooknum <= NF_INET_FORWARD && tstamp) {
 		struct nfulnl_msg_packet_timestamp ts;
-		struct timespec64 kts = ktime_to_timespec64(skb->tstamp);
+		struct timespec64 kts = ktime_to_timespec64(tstamp);
 		ts.sec = cpu_to_be64(kts.tv_sec);
 		ts.usec = cpu_to_be64(kts.tv_nsec / NSEC_PER_USEC);
 

net/netfilter/nfnetlink_queue.c

@@ -392,6 +392,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	bool csum_verify;
 	char *secdata = NULL;
 	u32 seclen = 0;
+	ktime_t tstamp;
 
 	size = nlmsg_total_size(sizeof(struct nfgenmsg))
 		+ nla_total_size(sizeof(struct nfqnl_msg_packet_hdr))
@@ -407,7 +408,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 		+ nla_total_size(sizeof(u_int32_t))	/* skbinfo */
 		+ nla_total_size(sizeof(u_int32_t));	/* cap_len */
 
-	if (entskb->tstamp)
+	tstamp = skb_tstamp_cond(entskb, false);
+	if (tstamp)
 		size += nla_total_size(sizeof(struct nfqnl_msg_packet_timestamp));
 
 	size += nfqnl_get_bridge_size(entry);
@@ -582,9 +584,9 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	if (nfqnl_put_bridge(entry, skb) < 0)
 		goto nla_put_failure;
 
-	if (entry->state.hook <= NF_INET_FORWARD && entskb->tstamp) {
+	if (entry->state.hook <= NF_INET_FORWARD && tstamp) {
 		struct nfqnl_msg_packet_timestamp ts;
-		struct timespec64 kts = ktime_to_timespec64(entskb->tstamp);
+		struct timespec64 kts = ktime_to_timespec64(tstamp);
 
 		ts.sec = cpu_to_be64(kts.tv_sec);
 		ts.usec = cpu_to_be64(kts.tv_nsec / NSEC_PER_USEC);