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, 9 insertions, 9 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 132be081cd00..704adad8f07f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -374,7 +374,7 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 {
         unsigned int mask;
         struct sock *sk = sock->sk;
-        struct tcp_sock *tp = tcp_sk(sk);
+        const struct tcp_sock *tp = tcp_sk(sk);
 
         sock_poll_wait(file, sk_sleep(sk), wait);
         if (sk->sk_state == TCP_LISTEN)
@@ -528,7 +528,7 @@ static inline void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb)
         tp->pushed_seq = tp->write_seq;
 }
 
-static inline int forced_push(struct tcp_sock *tp)
+static inline int forced_push(const struct tcp_sock *tp)
 {
         return after(tp->write_seq, tp->pushed_seq + (tp->max_window >> 1));
 }
@@ -891,9 +891,9 @@ EXPORT_SYMBOL(tcp_sendpage);
 #define TCP_PAGE(sk)    (sk->sk_sndmsg_page)
 #define TCP_OFF(sk)     (sk->sk_sndmsg_off)
 
-static inline int select_size(struct sock *sk, int sg)
+static inline int select_size(const struct sock *sk, int sg)
 {
-        struct tcp_sock *tp = tcp_sk(sk);
+        const struct tcp_sock *tp = tcp_sk(sk);
         int tmp = tp->mss_cache;
 
         if (sg) {
@@ -2408,7 +2408,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
 int tcp_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
                    unsigned int optlen)
 {
-        struct inet_connection_sock *icsk = inet_csk(sk);
+        const struct inet_connection_sock *icsk = inet_csk(sk);
 
         if (level != SOL_TCP)
                 return icsk->icsk_af_ops->setsockopt(sk, level, optname,
@@ -2430,9 +2430,9 @@ EXPORT_SYMBOL(compat_tcp_setsockopt);
 #endif
 
 /* Return information about state of tcp endpoint in API format. */
-void tcp_get_info(struct sock *sk, struct tcp_info *info)
+void tcp_get_info(const struct sock *sk, struct tcp_info *info)
 {
-        struct tcp_sock *tp = tcp_sk(sk);
+        const struct tcp_sock *tp = tcp_sk(sk);
         const struct inet_connection_sock *icsk = inet_csk(sk);
         u32 now = tcp_time_stamp;
 
@@ -3010,7 +3010,7 @@ int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
 EXPORT_SYMBOL(tcp_md5_hash_header);
 
 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
-                          struct sk_buff *skb, unsigned header_len)
+                          const struct sk_buff *skb, unsigned int header_len)
 {
         struct scatterlist sg;
         const struct tcphdr *tp = tcp_hdr(skb);
@@ -3043,7 +3043,7 @@ int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
 }
 EXPORT_SYMBOL(tcp_md5_hash_skb_data);
 
-int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, struct tcp_md5sig_key *key)
+int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *key)
 {
         struct scatterlist sg;