Merge branch 'net-remove-some-skb_mac_header-assumptions'

Eric Dumazet says:

====================
net: remove some skb_mac_header assumptions

Historically, we tried o maintain skb_mac_header available in most of
networking paths.

When reaching ndo_start_xmit() handlers, skb_mac_header() should always
be skb->data.

With recent additions of skb_mac_header_was_set() and
DEBUG_NET_WARN_ON_ONCE() in skb_mac_header(), we can attempt
to remove our reliance on skb_mac_header in TX paths.

When this effort completes we will remove skb_reset_mac_header()
from __dev_queue_xmit() and replace it by
skb_unset_mac_header() on DEBUG_NET builds.
====================

Link: https://lore.kernel.org/r/20230321164519.1286357-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/core/dev.c

@@ -3735,25 +3735,25 @@ static void qdisc_pkt_len_init(struct sk_buff *skb)
 	 * we add to pkt_len the headers size of all segments
 	 */
 	if (shinfo->gso_size && skb_transport_header_was_set(skb)) {
-		unsigned int hdr_len;
 		u16 gso_segs = shinfo->gso_segs;
+		unsigned int hdr_len;
 
 		/* mac layer + network layer */
-		hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
+		hdr_len = skb_transport_offset(skb);
 
 		/* + transport layer */
 		if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) {
 			const struct tcphdr *th;
 			struct tcphdr _tcphdr;
 
-			th = skb_header_pointer(skb, skb_transport_offset(skb),
+			th = skb_header_pointer(skb, hdr_len,
 						sizeof(_tcphdr), &_tcphdr);
 			if (likely(th))
 				hdr_len += __tcp_hdrlen(th);
 		} else {
 			struct udphdr _udphdr;
 
-			if (skb_header_pointer(skb, skb_transport_offset(skb),
+			if (skb_header_pointer(skb, hdr_len,
 					       sizeof(_udphdr), &_udphdr))
 				hdr_len += sizeof(struct udphdr);
 		}

net/sched/act_mirred.c

@@ -295,7 +295,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
 	at_nh = skb->data == skb_network_header(skb);
 	if (at_nh != expects_nh) {
 		mac_len = skb_at_tc_ingress(skb) ? skb->mac_len :
-			  skb_network_header(skb) - skb_mac_header(skb);
+			  skb_network_offset(skb);
 		if (expects_nh) {
 			/* target device/action expect data at nh */
 			skb_pull_rcsum(skb2, mac_len);

net/sched/act_mpls.c

@@ -69,7 +69,7 @@ TC_INDIRECT_SCOPE int tcf_mpls_act(struct sk_buff *skb,
 		skb_push_rcsum(skb, skb->mac_len);
 		mac_len = skb->mac_len;
 	} else {
-		mac_len = skb_network_header(skb) - skb_mac_header(skb);
+		mac_len = skb_network_offset(skb);
 	}
 
 	ret = READ_ONCE(m->tcf_action);

net/sched/sch_cake.c

@@ -1360,22 +1360,22 @@ static u32 cake_overhead(struct cake_sched_data *q, const struct sk_buff *skb)
 		return cake_calc_overhead(q, len, off);
 
 	/* borrowed from qdisc_pkt_len_init() */
-	hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
+	hdr_len = skb_transport_offset(skb);
 
 	/* + transport layer */
 	if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 |
 						SKB_GSO_TCPV6))) {
 		const struct tcphdr *th;
 		struct tcphdr _tcphdr;
 
-		th = skb_header_pointer(skb, skb_transport_offset(skb),
+		th = skb_header_pointer(skb, hdr_len,
 					sizeof(_tcphdr), &_tcphdr);
 		if (likely(th))
 			hdr_len += __tcp_hdrlen(th);
 	} else {
 		struct udphdr _udphdr;
 
-		if (skb_header_pointer(skb, skb_transport_offset(skb),
+		if (skb_header_pointer(skb, hdr_len,
 				       sizeof(_udphdr), &_udphdr))
 			hdr_len += sizeof(struct udphdr);
 	}