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Date:   Tue, 29 Aug 2017 16:27:07 -0700
From:   Tom Herbert <tom@...ntonium.net>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, Tom Herbert <tom@...ntonium.net>
Subject: [PATCH v2 net-next 2/6] udp: Constify skb argument in lookup functions

For UDP socket lookup functions, and associateed functions that take an
skbuf as argument, declare the skb argument as constant.

One caveat is that reuseport_select_sock can be called from the UDP
lookup functions with an skb argument. This function temporarily
modifies the skbuff data pointer (in bpf_run via a pull/push sequence).
To resolve compiler warning I added a local skbuf declaration that is
not const and assigned to the skb argument with an explicit cast.

Signed-off-by: Tom Herbert <tom@...ntonium.net>
---
 include/net/ip.h             |  2 +-
 include/net/sock_reuseport.h |  2 +-
 include/net/udp.h            | 11 ++++++-----
 net/core/sock_reuseport.c    |  5 +++--
 net/ipv4/udp.c               | 11 ++++++-----
 net/ipv6/udp.c               | 10 +++++-----
 6 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 9896f46cbbf1..8c0d84ffc659 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -79,7 +79,7 @@ struct ipcm_cookie {
 #define PKTINFO_SKB_CB(skb) ((struct in_pktinfo *)((skb)->cb))
 
 /* return enslaved device index if relevant */
-static inline int inet_sdif(struct sk_buff *skb)
+static inline int inet_sdif(const struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
 	if (skb && ipv4_l3mdev_skb(IPCB(skb)->flags))
diff --git a/include/net/sock_reuseport.h b/include/net/sock_reuseport.h
index aecd30308d50..d25352a848d9 100644
--- a/include/net/sock_reuseport.h
+++ b/include/net/sock_reuseport.h
@@ -20,7 +20,7 @@ extern int reuseport_add_sock(struct sock *sk, struct sock *sk2);
 extern void reuseport_detach_sock(struct sock *sk);
 extern struct sock *reuseport_select_sock(struct sock *sk,
 					  u32 hash,
-					  struct sk_buff *skb,
+					  const struct sk_buff *skb,
 					  int hdr_len);
 extern struct bpf_prog *reuseport_attach_prog(struct sock *sk,
 					      struct bpf_prog *prog);
diff --git a/include/net/udp.h b/include/net/udp.h
index 4e5f23fec35e..f3d1de6f0983 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -167,7 +167,7 @@ static inline void udp_csum_pull_header(struct sk_buff *skb)
 	UDP_SKB_CB(skb)->cscov -= sizeof(struct udphdr);
 }
 
-typedef struct sock *(*udp_lookup_t)(struct sk_buff *skb, __be16 sport,
+typedef struct sock *(*udp_lookup_t)(const struct sk_buff *skb, __be16 sport,
 				     __be16 dport);
 
 struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
@@ -288,8 +288,9 @@ struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
 			     __be32 daddr, __be16 dport, int dif);
 struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
 			       __be32 daddr, __be16 dport, int dif, int sdif,
-			       struct udp_table *tbl, struct sk_buff *skb);
-struct sock *udp4_lib_lookup_skb(struct sk_buff *skb,
+			       struct udp_table *tbl,
+			       const struct sk_buff *skb);
+struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport);
 struct sock *udp6_lib_lookup(struct net *net,
 			     const struct in6_addr *saddr, __be16 sport,
@@ -299,8 +300,8 @@ struct sock *__udp6_lib_lookup(struct net *net,
 			       const struct in6_addr *saddr, __be16 sport,
 			       const struct in6_addr *daddr, __be16 dport,
 			       int dif, int sdif, struct udp_table *tbl,
-			       struct sk_buff *skb);
-struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
+			       const struct sk_buff *skb);
+struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport);
 
 /* UDP uses skb->dev_scratch to cache as much information as possible and avoid
diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index eed1ebf7f29d..a17f13b33189 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -164,9 +164,10 @@ void reuseport_detach_sock(struct sock *sk)
 EXPORT_SYMBOL(reuseport_detach_sock);
 
 static struct sock *run_bpf(struct sock_reuseport *reuse, u16 socks,
-			    struct bpf_prog *prog, struct sk_buff *skb,
+			    struct bpf_prog *prog, const struct sk_buff *_skb,
 			    int hdr_len)
 {
+	struct sk_buff *skb = (struct sk_buff *)_skb; /* Override const */
 	struct sk_buff *nskb = NULL;
 	u32 index;
 
@@ -205,7 +206,7 @@ static struct sock *run_bpf(struct sock_reuseport *reuse, u16 socks,
  */
 struct sock *reuseport_select_sock(struct sock *sk,
 				   u32 hash,
-				   struct sk_buff *skb,
+				   const struct sk_buff *skb,
 				   int hdr_len)
 {
 	struct sock_reuseport *reuse;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index bf6c406bf5e7..a851026ef28b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -135,7 +135,8 @@ EXPORT_SYMBOL(udp_memory_allocated);
 #define PORTS_PER_CHAIN (MAX_UDP_PORTS / UDP_HTABLE_SIZE_MIN)
 
 /* IPCB reference means this can not be used from early demux */
-static bool udp_lib_exact_dif_match(struct net *net, struct sk_buff *skb)
+static bool udp_lib_exact_dif_match(struct net *net,
+				    const struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
 	if (!net->ipv4.sysctl_udp_l3mdev_accept &&
@@ -445,7 +446,7 @@ static struct sock *udp4_lib_lookup2(struct net *net,
 				     __be32 daddr, unsigned int hnum,
 				     int dif, int sdif, bool exact_dif,
 				     struct udp_hslot *hslot2,
-				     struct sk_buff *skb)
+				     const struct sk_buff *skb)
 {
 	struct sock *sk, *result;
 	int score, badness, matches = 0, reuseport = 0;
@@ -484,7 +485,7 @@ static struct sock *udp4_lib_lookup2(struct net *net,
  */
 struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
 		__be16 sport, __be32 daddr, __be16 dport, int dif,
-		int sdif, struct udp_table *udptable, struct sk_buff *skb)
+		int sdif, struct udp_table *udptable, const struct sk_buff *skb)
 {
 	struct sock *sk, *result;
 	unsigned short hnum = ntohs(dport);
@@ -552,7 +553,7 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
 }
 EXPORT_SYMBOL_GPL(__udp4_lib_lookup);
 
-static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
+static inline struct sock *__udp4_lib_lookup_skb(const struct sk_buff *skb,
 						 __be16 sport, __be16 dport,
 						 struct udp_table *udptable)
 {
@@ -563,7 +564,7 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
 				 inet_sdif(skb), udptable, skb);
 }
 
-struct sock *udp4_lib_lookup_skb(struct sk_buff *skb,
+struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport)
 {
 	return __udp4_lib_lookup_skb(skb, sport, dport, &udp_table);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 976f30391356..e9aa4db3ba53 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -56,7 +56,7 @@
 #include <trace/events/skb.h>
 #include "udp_impl.h"
 
-static bool udp6_lib_exact_dif_match(struct net *net, struct sk_buff *skb)
+static bool udp6_lib_exact_dif_match(struct net *net, const struct sk_buff *skb)
 {
 #if defined(CONFIG_NET_L3_MASTER_DEV)
 	if (!net->ipv4.sysctl_udp_l3mdev_accept &&
@@ -181,7 +181,7 @@ static struct sock *udp6_lib_lookup2(struct net *net,
 		const struct in6_addr *saddr, __be16 sport,
 		const struct in6_addr *daddr, unsigned int hnum,
 		int dif, int sdif, bool exact_dif,
-		struct udp_hslot *hslot2, struct sk_buff *skb)
+		struct udp_hslot *hslot2, const struct sk_buff *skb)
 {
 	struct sock *sk, *result;
 	int score, badness, matches = 0, reuseport = 0;
@@ -221,7 +221,7 @@ struct sock *__udp6_lib_lookup(struct net *net,
 			       const struct in6_addr *saddr, __be16 sport,
 			       const struct in6_addr *daddr, __be16 dport,
 			       int dif, int sdif, struct udp_table *udptable,
-			       struct sk_buff *skb)
+			       const struct sk_buff *skb)
 {
 	struct sock *sk, *result;
 	unsigned short hnum = ntohs(dport);
@@ -290,7 +290,7 @@ struct sock *__udp6_lib_lookup(struct net *net,
 }
 EXPORT_SYMBOL_GPL(__udp6_lib_lookup);
 
-static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,
+static struct sock *__udp6_lib_lookup_skb(const struct sk_buff *skb,
 					  __be16 sport, __be16 dport,
 					  struct udp_table *udptable)
 {
@@ -301,7 +301,7 @@ static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,
 				 inet6_sdif(skb), udptable, skb);
 }
 
-struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
+struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport)
 {
 	const struct ipv6hdr *iph = ipv6_hdr(skb);
-- 
2.11.0

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