netdev - [PATCH RFC 7/9] sk_buff: move inner header fields after tail

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Message-Id: <99ff8a613938fd5bb670e1e7b4e3bb79770c5078.1626882513.git.pabeni@redhat.com>
Date:   Wed, 21 Jul 2021 18:44:39 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Florian Westphal <fw@...len.de>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Subject: [PATCH RFC 7/9] sk_buff: move inner header fields after tail

all the inner header fields are valid only if the 'encaspulation'
flag is set, and the relevant fields are always initialized when
the field is set: we don't need to initialize them at skb allocation
time

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 v1 -> v2:
  - add CHECK_SKB_FIELD(__encapsulation_offset) in __copy_skb_header
---
 include/linux/skbuff.h | 31 ++++++++++++++++++++++---------
 net/core/skbuff.c      |  6 ++----
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ea9fdcc7c7ca..a3e756575aa7 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -822,6 +822,9 @@ struct sk_buff {
 	__u8			ip_summed:2;
 	__u8			ooo_okay:1;
 
+	/* private: */
+	__u8			__pkt_encapsulation_offset[0];
+	/* public: */
 	__u8			l4_hash:1;
 	__u8			sw_hash:1;
 	__u8			wifi_acked_valid:1;
@@ -911,15 +914,6 @@ struct sk_buff {
 		__u32		reserved_tailroom;
 	};
 
-	union {
-		__be16		inner_protocol;
-		__u8		inner_ipproto;
-	};
-
-	__u16			inner_transport_header;
-	__u16			inner_network_header;
-	__u16			inner_mac_header;
-
 	__be16			protocol;
 	__u16			transport_header;
 	__u16			network_header;
@@ -948,6 +942,19 @@ struct sk_buff {
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 	unsigned long		 _nfct;
 #endif
+	union {
+		struct {
+			union {
+			__be16	inner_protocol;
+			__u8	inner_ipproto;
+			};
+
+			__u16	inner_transport_header;
+			__u16	inner_network_header;
+			__u16	inner_mac_header;
+		};
+		__u64		inner_headers;
+	};
 };
 
 #ifdef __KERNEL__
@@ -2449,6 +2456,12 @@ static inline void skb_tailroom_reserve(struct sk_buff *skb, unsigned int mtu,
 #define ENCAP_TYPE_ETHER	0
 #define ENCAP_TYPE_IPPROTO	1
 
+static inline void __skb_copy_inner_headers(struct sk_buff *dst, const struct sk_buff *src)
+{
+	if (src->encapsulation)
+		dst->inner_headers = src->inner_headers;
+}
+
 static inline void skb_set_inner_protocol(struct sk_buff *skb,
 					  __be16 protocol)
 {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9ed754da6e13..53b8db10e567 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -995,6 +995,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 	skb_dst_copy(new, old);
 	__skb_ext_copy(new, old);
 	__nf_copy(new, old, false);
+	__skb_copy_inner_headers(new, old);
 
 	/* Note : this field could be in headers_start/headers_end section
 	 * It is not yet because we do not want to have a 16 bit hole
@@ -1005,6 +1006,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 	       offsetof(struct sk_buff, headers_end) -
 	       offsetof(struct sk_buff, headers_start));
 	CHECK_SKB_FIELD(_state);
+	CHECK_SKB_FIELD(__pkt_encapsulation_offset);
 	CHECK_SKB_FIELD(protocol);
 	CHECK_SKB_FIELD(csum);
 	CHECK_SKB_FIELD(hash);
@@ -1015,10 +1017,6 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 	CHECK_SKB_FIELD(transport_header);
 	CHECK_SKB_FIELD(network_header);
 	CHECK_SKB_FIELD(mac_header);
-	CHECK_SKB_FIELD(inner_protocol);
-	CHECK_SKB_FIELD(inner_transport_header);
-	CHECK_SKB_FIELD(inner_network_header);
-	CHECK_SKB_FIELD(inner_mac_header);
 	CHECK_SKB_FIELD(mark);
 #ifdef CONFIG_NETWORK_SECMARK
 	CHECK_SKB_FIELD(secmark);
-- 
2.26.3