Merge branch 'net-gro-remove-network_header-use-move-p-flush-flush_id-calculations-to-l4'

Richard Gobert says:

====================
net: gro: remove network_header use, move p->{flush/flush_id} calculations to L4

The cb fields network_offset and inner_network_offset are used instead of
skb->network_header throughout GRO.

These fields are then leveraged in the next commit to remove flush_id state
from napi_gro_cb, and stateful code in {ipv6,inet}_gro_receive which may be
unnecessarily complicated due to encapsulation support in GRO. These fields
are checked in L4 instead.

3rd patch adds tests for different flush_id flows in GRO.
====================

Link: https://lore.kernel.org/r/20240509190819.2985-1-richardbgobert@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 75 insertions, 10 deletions

diff --git a/include/net/gro.h b/include/net/gro.h
index 5df8bf318197..f13634b1f4c1 100644
--- a/include/net/gro.h
+++ b/include/net/gro.h
@@ -36,15 +36,15 @@ struct napi_gro_cb {
 	/* This is non-zero if the packet cannot be merged with the new skb. */
 	u16	flush;
 
-	/* Save the IP ID here and check when we get to the transport layer */
-	u16	flush_id;
-
 	/* Number of segments aggregated. */
 	u16	count;
 
 	/* Used in ipv6_gro_receive() and foo-over-udp and esp-in-udp */
 	u16	proto;
 
+	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
+	__wsum	csum;
+
 /* Used in napi_gro_cb::free */
 #define NAPI_GRO_FREE             1
 #define NAPI_GRO_FREE_STOLEN_HEAD 2
@@ -75,8 +75,8 @@ struct napi_gro_cb {
 		/* Used in GRE, set in fou/gue_gro_receive */
 		u8	is_fou:1;
 
-		/* Used to determine if flush_id can be ignored */
-		u8	is_atomic:1;
+		/* Used to determine if ipid_offset can be ignored */
+		u8	ip_fixedid:1;
 
 		/* Number of gro_receive callbacks this packet already went through */
 		u8 recursion_counter:4;
@@ -85,9 +85,6 @@ struct napi_gro_cb {
 		u8	is_flist:1;
 	);
 
-	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
-	__wsum	csum;
-
 	/* L3 offsets */
 	union {
 		struct {
@@ -181,12 +178,17 @@ static inline void *skb_gro_header(struct sk_buff *skb, unsigned int hlen,
 	return ptr;
 }
 
+static inline int skb_gro_receive_network_offset(const struct sk_buff *skb)
+{
+	return NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark];
+}
+
 static inline void *skb_gro_network_header(const struct sk_buff *skb)
 {
 	if (skb_gro_may_pull(skb, skb_gro_offset(skb)))
-		return skb_gro_header_fast(skb, skb_network_offset(skb));
+		return skb_gro_header_fast(skb, skb_gro_receive_network_offset(skb));
 
-	return skb_network_header(skb);
+	return skb->data + skb_gro_receive_network_offset(skb);
 }
 
 static inline __wsum inet_gro_compute_pseudo(const struct sk_buff *skb,
@@ -437,6 +439,69 @@ static inline __wsum ip6_gro_compute_pseudo(const struct sk_buff *skb,
 					    skb_gro_len(skb), proto, 0));
 }
 
+static inline int inet_gro_flush(const struct iphdr *iph, const struct iphdr *iph2,
+				 struct sk_buff *p, bool outer)
+{
+	const u32 id = ntohl(*(__be32 *)&iph->id);
+	const u32 id2 = ntohl(*(__be32 *)&iph2->id);
+	const u16 ipid_offset = (id >> 16) - (id2 >> 16);
+	const u16 count = NAPI_GRO_CB(p)->count;
+	const u32 df = id & IP_DF;
+	int flush;
+
+	/* All fields must match except length and checksum. */
+	flush = (iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF));
+
+	if (flush | (outer && df))
+		return flush;
+
+	/* When we receive our second frame we can make a decision on if we
+	 * continue this flow as an atomic flow with a fixed ID or if we use
+	 * an incrementing ID.
+	 */
+	if (count == 1 && df && !ipid_offset)
+		NAPI_GRO_CB(p)->ip_fixedid = true;
+
+	return ipid_offset ^ (count * !NAPI_GRO_CB(p)->ip_fixedid);
+}
+
+static inline int ipv6_gro_flush(const struct ipv6hdr *iph, const struct ipv6hdr *iph2)
+{
+	/* <Version:4><Traffic_Class:8><Flow_Label:20> */
+	__be32 first_word = *(__be32 *)iph ^ *(__be32 *)iph2;
+
+	/* Flush if Traffic Class fields are different. */
+	return !!((first_word & htonl(0x0FF00000)) |
+		(__force __be32)(iph->hop_limit ^ iph2->hop_limit));
+}
+
+static inline int __gro_receive_network_flush(const void *th, const void *th2,
+					      struct sk_buff *p, const u16 diff,
+					      bool outer)
+{
+	const void *nh = th - diff;
+	const void *nh2 = th2 - diff;
+
+	if (((struct iphdr *)nh)->version == 6)
+		return ipv6_gro_flush(nh, nh2);
+	else
+		return inet_gro_flush(nh, nh2, p, outer);
+}
+
+static inline int gro_receive_network_flush(const void *th, const void *th2,
+					    struct sk_buff *p)
+{
+	const bool encap_mark = NAPI_GRO_CB(p)->encap_mark;
+	int off = skb_transport_offset(p);
+	int flush;
+
+	flush = __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->network_offset, encap_mark);
+	if (encap_mark)
+		flush |= __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->inner_network_offset, false);
+
+	return flush;
+}
+
 int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb);
 int skb_gro_receive_list(struct sk_buff *p, struct sk_buff *skb);