[TCP]: Allow choosing TCP congestion control via sockopt.

Allow using setsockopt to set TCP congestion control to use on a per
socket basis.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 75 insertions, 4 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f3dbc8dc1263..882436da9a3a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1927,6 +1927,25 @@ int tcp_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
                 return tp->af_specific->setsockopt(sk, level, optname,
                                                    optval, optlen);
 
+        /* This is a string value all the others are int's */
+        if (optname == TCP_CONGESTION) {
+                char name[TCP_CA_NAME_MAX];
+
+                if (optlen < 1)
+                        return -EINVAL;
+
+                val = strncpy_from_user(name, optval,
+                                        min(TCP_CA_NAME_MAX-1, optlen));
+                if (val < 0)
+                        return -EFAULT;
+                name[val] = 0;
+
+                lock_sock(sk);
+                err = tcp_set_congestion_control(tp, name);
+                release_sock(sk);
+                return err;
+        }
+
         if (optlen < sizeof(int))
                 return -EINVAL;
 
@@ -2211,6 +2230,16 @@ int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval,
         case TCP_QUICKACK:
                 val = !tp->ack.pingpong;
                 break;
+
+        case TCP_CONGESTION:
+                if (get_user(len, optlen))
+                        return -EFAULT;
+                len = min_t(unsigned int, len, TCP_CA_NAME_MAX);
+                if (put_user(len, optlen))
+                        return -EFAULT;
+                if (copy_to_user(optval, tp->ca_ops->name, len))
+                        return -EFAULT;
+                return 0;
         default:
                 return -ENOPROTOOPT;
         };
@@ -2224,7 +2253,7 @@ int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval,
 
 
 extern void __skb_cb_too_small_for_tcp(int, int);
-extern void tcpdiag_init(void);
+extern struct tcp_congestion_ops tcp_reno;
 
 static __initdata unsigned long thash_entries;
 static int __init set_thash_entries(char *str)
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 665394a63ae4..4970d10a7785 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -21,7 +21,7 @@ static struct tcp_congestion_ops *tcp_ca_find(const char *name)
 {
         struct tcp_congestion_ops *e;
 
-        list_for_each_entry(e, &tcp_cong_list, list) {
+        list_for_each_entry_rcu(e, &tcp_cong_list, list) {
                 if (strcmp(e->name, name) == 0)
                         return e;
         }
@@ -77,6 +77,9 @@ void tcp_init_congestion_control(struct tcp_sock *tp)
 {
         struct tcp_congestion_ops *ca;
 
+        if (tp->ca_ops != &tcp_init_congestion_ops)
+                return;
+
         rcu_read_lock();
         list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
                 if (try_module_get(ca->owner)) {
@@ -139,6 +142,34 @@ void tcp_get_default_congestion_control(char *name)
         rcu_read_unlock();
 }
 
+/* Change congestion control for socket */
+int tcp_set_congestion_control(struct tcp_sock *tp, const char *name)
+{
+        struct tcp_congestion_ops *ca;
+        int err = 0;
+
+        rcu_read_lock();
+        ca = tcp_ca_find(name);
+        if (ca == tp->ca_ops)
+                goto out;
+
+        if (!ca)
+                err = -ENOENT;
+
+        else if (!try_module_get(ca->owner))
+                err = -EBUSY;
+
+        else {
+                tcp_cleanup_congestion_control(tp);
+                tp->ca_ops = ca;
+                if (tp->ca_ops->init)
+                        tp->ca_ops->init(tp);
+        }
+ out:
+        rcu_read_unlock();
+        return err;
+}
+
 /*
  * TCP Reno congestion control
  * This is special case used for fallback as well.
@@ -192,4 +223,15 @@ struct tcp_congestion_ops tcp_reno = {
         .min_cwnd       = tcp_reno_min_cwnd,
 };
 
-EXPORT_SYMBOL_GPL(tcp_reno);
+/* Initial congestion control used (until SYN)
+ * really reno under another name so we can tell difference
+ * during tcp_set_default_congestion_control
+ */
+struct tcp_congestion_ops tcp_init_congestion_ops  = {
+        .name           = "",
+        .owner          = THIS_MODULE,
+        .ssthresh       = tcp_reno_ssthresh,
+        .cong_avoid     = tcp_reno_cong_avoid,
+        .min_cwnd       = tcp_reno_min_cwnd,
+};
+EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 9122814c13ad..ebf112347a97 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2048,7 +2048,7 @@ static int tcp_v4_init_sock(struct sock *sk)
         tp->mss_cache_std = tp->mss_cache = 536;
 
         tp->reordering = sysctl_tcp_reordering;
-        tp->ca_ops = &tcp_reno;
+        tp->ca_ops = &tcp_init_congestion_ops;
 
         sk->sk_state = TCP_CLOSE;