Subject: [PATCH v2] net: gro: skb_gro_header helper function

From: Richard Gobert <[email-masked]>
Date: Tue, 2 Aug 2022 16:38:02 +0200

Introduce a simple helper function to replace a common pattern.
When accessing the GRO header, we fetch the pointer from frag0,
then test its validity and fetch it from the skb when necessary.

This leads to the pattern
skb_gro_header_fast -> skb_gro_header_hard -> skb_gro_header_slow
recurring many times throughout GRO code.

This patch replaces these patterns with a single inlined function
call, improving code readability.

Signed-off-by: Richard Gobert <[email-masked]>
---
 drivers/net/geneve.c           |  9 +++------
 drivers/net/vxlan/vxlan_core.c |  9 +++------
 include/net/gro.h              | 33 ++++++++++++++++++---------------
 net/8021q/vlan_core.c          |  9 +++------
 net/ethernet/eth.c             |  9 +++------
 net/ipv4/af_inet.c             |  9 +++------
 net/ipv4/fou.c                 |  9 +++------
 net/ipv4/gre_offload.c         |  9 +++------
 net/ipv4/tcp_offload.c         |  9 +++------
 net/ipv6/ip6_offload.c         |  9 +++------
 10 files changed, 45 insertions(+), 69 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 2495a5719e1c..98c18a7a27d3 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -503,12 +503,9 @@ static struct sk_buff *geneve_gro_receive(struct sock *sk,
 
 	off_gnv = skb_gro_offset(skb);
 	hlen = off_gnv + sizeof(*gh);
-	gh = skb_gro_header_fast(skb, off_gnv);
-	if (skb_gro_header_hard(skb, hlen)) {
-		gh = skb_gro_header_slow(skb, hlen, off_gnv);
-		if (unlikely(!gh))
-			goto out;
-	}
+	gh = skb_gro_header(skb, hlen, off_gnv);
+	if (unlikely(!gh))
+		goto out;
 
 	if (gh->ver != GENEVE_VER || gh->oam)
 		goto out;
diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 8a5e3a6d32d7..b55d7ddab12a 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -713,12 +713,9 @@ static struct sk_buff *vxlan_gro_receive(struct sock *sk,
 
 	off_vx = skb_gro_offset(skb);
 	hlen = off_vx + sizeof(*vh);
-	vh   = skb_gro_header_fast(skb, off_vx);
-	if (skb_gro_header_hard(skb, hlen)) {
-		vh = skb_gro_header_slow(skb, hlen, off_vx);
-		if (unlikely(!vh))
-			goto out;
-	}
+	vh = skb_gro_header(skb, hlen, off_vx);
+	if (unlikely(!vh))
+		goto out;
 
 	skb_gro_postpull_rcsum(skb, vh, sizeof(struct vxlanhdr));
 
diff --git a/include/net/gro.h b/include/net/gro.h
index 867656b0739c..5bf15c212434 100644
--- a/include/net/gro.h
+++ b/include/net/gro.h
@@ -160,6 +160,17 @@ static inline void *skb_gro_header_slow(struct sk_buff *skb, unsigned int hlen,
 	return skb->data + offset;
 }
 
+static inline void *skb_gro_header(struct sk_buff *skb,
+					unsigned int hlen, unsigned int offset)
+{
+	void *ptr;
+
+	ptr = skb_gro_header_fast(skb, offset);
+	if (skb_gro_header_hard(skb, hlen))
+		ptr = skb_gro_header_slow(skb, hlen, offset);
+	return ptr;
+}
+
 static inline void *skb_gro_network_header(struct sk_buff *skb)
 {
 	return (NAPI_GRO_CB(skb)->frag0 ?: skb->data) +
@@ -301,12 +312,9 @@ static inline void *skb_gro_remcsum_process(struct sk_buff *skb, void *ptr,
 		return ptr;
 	}
 
-	ptr = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, off + plen)) {
-		ptr = skb_gro_header_slow(skb, off + plen, off);
-		if (!ptr)
-			return NULL;
-	}
+	ptr = skb_gro_header(skb, off + plen, off);
+	if (!ptr)
+		return NULL;
 
 	delta = remcsum_adjust(ptr + hdrlen, NAPI_GRO_CB(skb)->csum,
 			       start, offset);
@@ -329,12 +337,9 @@ static inline void skb_gro_remcsum_cleanup(struct sk_buff *skb,
 	if (!grc->delta)
 		return;
 
-	ptr = skb_gro_header_fast(skb, grc->offset);
-	if (skb_gro_header_hard(skb, grc->offset + sizeof(u16))) {
-		ptr = skb_gro_header_slow(skb, plen, grc->offset);
-		if (!ptr)
-			return;
-	}
+	ptr = skb_gro_header(skb, plen, grc->offset);
+	if (!ptr)
+		return;
 
 	remcsum_unadjust((__sum16 *)ptr, grc->delta);
 }
@@ -405,9 +410,7 @@ static inline struct udphdr *udp_gro_udphdr(struct sk_buff *skb)
 
 	off  = skb_gro_offset(skb);
 	hlen = off + sizeof(*uh);
-	uh   = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, hlen))
-		uh = skb_gro_header_slow(skb, hlen, off);
+	uh   = skb_gro_header(skb, hlen, off);
 
 	return uh;
 }
diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index acf8c791f320..91506dd11156 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -467,12 +467,9 @@ static struct sk_buff *vlan_gro_receive(struct list_head *head,
 
 	off_vlan = skb_gro_offset(skb);
 	hlen = off_vlan + sizeof(*vhdr);
-	vhdr = skb_gro_header_fast(skb, off_vlan);
-	if (skb_gro_header_hard(skb, hlen)) {
-		vhdr = skb_gro_header_slow(skb, hlen, off_vlan);
-		if (unlikely(!vhdr))
-			goto out;
-	}
+	vhdr = skb_gro_header(skb, hlen, off_vlan);
+	if (unlikely(!vhdr))
+		goto out;
 
 	type = vhdr->h_vlan_encapsulated_proto;
 
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 62b89d6f54fd..e02daa74e833 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -414,12 +414,9 @@ struct sk_buff *eth_gro_receive(struct list_head *head, struct sk_buff *skb)
 
 	off_eth = skb_gro_offset(skb);
 	hlen = off_eth + sizeof(*eh);
-	eh = skb_gro_header_fast(skb, off_eth);
-	if (skb_gro_header_hard(skb, hlen)) {
-		eh = skb_gro_header_slow(skb, hlen, off_eth);
-		if (unlikely(!eh))
-			goto out;
-	}
+	eh = skb_gro_header(skb, hlen, off_eth);
+	if (unlikely(!eh))
+		goto out;
 
 	flush = 0;
 
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 93da9f783bec..59488f888e12 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1447,12 +1447,9 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
 
 	off = skb_gro_offset(skb);
 	hlen = off + sizeof(*iph);
-	iph = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, hlen)) {
-		iph = skb_gro_header_slow(skb, hlen, off);
-		if (unlikely(!iph))
-			goto out;
-	}
+	iph = skb_gro_header(skb, hlen, off);
+	if (unlikely(!iph))
+		goto out;
 
 	proto = iph->protocol;
 
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 025a33c1b04d..cb5bfb77944c 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -323,12 +323,9 @@ static struct sk_buff *gue_gro_receive(struct sock *sk,
 	off = skb_gro_offset(skb);
 	len = off + sizeof(*guehdr);
 
-	guehdr = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, len)) {
-		guehdr = skb_gro_header_slow(skb, len, off);
-		if (unlikely(!guehdr))
-			goto out;
-	}
+	guehdr = skb_gro_header(skb, len, off);
+	if (unlikely(!guehdr))
+		goto out;
 
 	switch (guehdr->version) {
 	case 0:
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 07073fa35205..2b9cb5398335 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -137,12 +137,9 @@ static struct sk_buff *gre_gro_receive(struct list_head *head,
 
 	off = skb_gro_offset(skb);
 	hlen = off + sizeof(*greh);
-	greh = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, hlen)) {
-		greh = skb_gro_header_slow(skb, hlen, off);
-		if (unlikely(!greh))
-			goto out;
-	}
+	greh = skb_gro_header(skb, hlen, off);
+	if (unlikely(!greh))
+		goto out;
 
 	/* Only support version 0 and K (key), C (csum) flags. Note that
 	 * although the support for the S (seq#) flag can be added easily
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 30abde86db45..a844a0d38482 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -195,12 +195,9 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
 
 	off = skb_gro_offset(skb);
 	hlen = off + sizeof(*th);
-	th = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, hlen)) {
-		th = skb_gro_header_slow(skb, hlen, off);
-		if (unlikely(!th))
-			goto out;
-	}
+	th = skb_gro_header(skb, hlen, off);
+	if (unlikely(!th))
+		goto out;
 
 	thlen = th->doff * 4;
 	if (thlen < sizeof(*th))
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index c4fc03c1ac99..616d17b8ca5e 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -197,12 +197,9 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head,
 
 	off = skb_gro_offset(skb);
 	hlen = off + sizeof(*iph);
-	iph = skb_gro_header_fast(skb, off);
-	if (skb_gro_header_hard(skb, hlen)) {
-		iph = skb_gro_header_slow(skb, hlen, off);
-		if (unlikely(!iph))
-			goto out;
-	}
+	iph = skb_gro_header_slow(skb, hlen, off);
+	if (unlikely(!iph))
+		goto out;
 
 	skb_set_network_header(skb, off);
 	skb_gro_pull(skb, sizeof(*iph));
-- 
2.20.1