tcp: add const qualifiers where possible

Adding const qualifiers to pointers can ease code review, and spot some
bugs. It might allow compiler to optimize code further.

For example, is it legal to temporary write a null cksum into tcphdr
in tcp_md5_hash_header() ? I am afraid a sniffer could catch the
temporary null value...

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 13 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 48da7cc..955c925 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -104,7 +104,7 @@ struct tcp_md5sig_key *tcp_v4_md5_do_lookup(struct sock *sk, __be32 addr)
 struct inet_hashinfo tcp_hashinfo;
 EXPORT_SYMBOL(tcp_hashinfo);
 
-static inline __u32 tcp_v4_init_sequence(struct sk_buff *skb)
+static inline __u32 tcp_v4_init_sequence(const struct sk_buff *skb)
 {
 	return secure_tcp_sequence_number(ip_hdr(skb)->daddr,
 					  ip_hdr(skb)->saddr,
@@ -552,7 +552,7 @@ static void __tcp_v4_send_check(struct sk_buff *skb,
 /* This routine computes an IPv4 TCP checksum. */
 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
 {
-	struct inet_sock *inet = inet_sk(sk);
+	const struct inet_sock *inet = inet_sk(sk);
 
 	__tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
 }
@@ -590,7 +590,7 @@ int tcp_v4_gso_send_check(struct sk_buff *skb)
 
 static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb)
 {
-	struct tcphdr *th = tcp_hdr(skb);
+	const struct tcphdr *th = tcp_hdr(skb);
 	struct {
 		struct tcphdr th;
 #ifdef CONFIG_TCP_MD5SIG
@@ -668,7 +668,7 @@ static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
 			    struct tcp_md5sig_key *key,
 			    int reply_flags)
 {
-	struct tcphdr *th = tcp_hdr(skb);
+	const struct tcphdr *th = tcp_hdr(skb);
 	struct {
 		struct tcphdr th;
 		__be32 opt[(TCPOLEN_TSTAMP_ALIGNED >> 2)
@@ -1182,10 +1182,10 @@ static int tcp_v4_inbound_md5_hash(struct sock *sk, struct sk_buff *skb)
 	 * o MD5 hash and we're not expecting one.
 	 * o MD5 hash and its wrong.
 	 */
-	__u8 *hash_location = NULL;
+	const __u8 *hash_location = NULL;
 	struct tcp_md5sig_key *hash_expected;
 	const struct iphdr *iph = ip_hdr(skb);
-	struct tcphdr *th = tcp_hdr(skb);
+	const struct tcphdr *th = tcp_hdr(skb);
 	int genhash;
 	unsigned char newhash[16];
 
@@ -1248,7 +1248,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_extend_values tmp_ext;
 	struct tcp_options_received tmp_opt;
-	u8 *hash_location;
+	const u8 *hash_location;
 	struct request_sock *req;
 	struct inet_request_sock *ireq;
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -1645,7 +1645,7 @@ EXPORT_SYMBOL(tcp_v4_do_rcv);
 int tcp_v4_rcv(struct sk_buff *skb)
 {
 	const struct iphdr *iph;
-	struct tcphdr *th;
+	const struct tcphdr *th;
 	struct sock *sk;
 	int ret;
 	struct net *net = dev_net(skb->dev);
@@ -1809,7 +1809,7 @@ EXPORT_SYMBOL(tcp_v4_get_peer);
 
 void *tcp_v4_tw_get_peer(struct sock *sk)
 {
-	struct inet_timewait_sock *tw = inet_twsk(sk);
+	const struct inet_timewait_sock *tw = inet_twsk(sk);
 
 	return inet_getpeer_v4(tw->tw_daddr, 1);
 }
@@ -2381,7 +2381,7 @@ void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo)
 }
 EXPORT_SYMBOL(tcp_proc_unregister);
 
-static void get_openreq4(struct sock *sk, struct request_sock *req,
+static void get_openreq4(const struct sock *sk, const struct request_sock *req,
 			 struct seq_file *f, int i, int uid, int *len)
 {
 	const struct inet_request_sock *ireq = inet_rsk(req);
@@ -2411,9 +2411,9 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
 {
 	int timer_active;
 	unsigned long timer_expires;
-	struct tcp_sock *tp = tcp_sk(sk);
+	const struct tcp_sock *tp = tcp_sk(sk);
 	const struct inet_connection_sock *icsk = inet_csk(sk);
-	struct inet_sock *inet = inet_sk(sk);
+	const struct inet_sock *inet = inet_sk(sk);
 	__be32 dest = inet->inet_daddr;
 	__be32 src = inet->inet_rcv_saddr;
 	__u16 destp = ntohs(inet->inet_dport);
@@ -2462,7 +2462,7 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
 		len);
 }
 
-static void get_timewait4_sock(struct inet_timewait_sock *tw,
+static void get_timewait4_sock(const struct inet_timewait_sock *tw,
 			       struct seq_file *f, int i, int *len)
 {
 	__be32 dest, src;