net-2.6: SYN retransmits: Add new parameter to retransmits_timed_out()

Fixes kernel Bugzilla Bug 18952

This patch adds a syn_set parameter to the retransmits_timed_out()
routine and updates its callers. If not set, TCP_RTO_MIN is taken
as the calculation basis as before. If set, TCP_TIMEOUT_INIT is
used instead, so that sysctl_syn_retries represents the actual
amount of SYN retransmissions in case no SYNACKs are received when
establishing a new connection.

Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 10 deletions

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index c35b469e851c..74c54b30600f 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -135,13 +135,16 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
 
 /* This function calculates a "timeout" which is equivalent to the timeout of a
  * TCP connection after "boundary" unsuccessful, exponentially backed-off
- * retransmissions with an initial RTO of TCP_RTO_MIN.
+ * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if
+ * syn_set flag is set.
  */
 static bool retransmits_timed_out(struct sock *sk,
-                                  unsigned int boundary)
+                                  unsigned int boundary,
+                                  bool syn_set)
 {
         unsigned int timeout, linear_backoff_thresh;
         unsigned int start_ts;
+        unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN;
 
         if (!inet_csk(sk)->icsk_retransmits)
                 return false;
@@ -151,12 +154,12 @@ static bool retransmits_timed_out(struct sock *sk,
         else
                 start_ts = tcp_sk(sk)->retrans_stamp;
 
-        linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);
+        linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);
 
         if (boundary <= linear_backoff_thresh)
-                timeout = ((2 << boundary) - 1) * TCP_RTO_MIN;
+                timeout = ((2 << boundary) - 1) * rto_base;
         else
-                timeout = ((2 << linear_backoff_thresh) - 1) * TCP_RTO_MIN +
+                timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
                           (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
 
         return (tcp_time_stamp - start_ts) >= timeout;
@@ -167,14 +170,15 @@ static int tcp_write_timeout(struct sock *sk)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         int retry_until;
-        bool do_reset;
+        bool do_reset, syn_set = 0;
 
         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
                 if (icsk->icsk_retransmits)
                         dst_negative_advice(sk);
                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
+                syn_set = 1;
         } else {
-                if (retransmits_timed_out(sk, sysctl_tcp_retries1)) {
+                if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0)) {
                         /* Black hole detection */
                         tcp_mtu_probing(icsk, sk);
 
@@ -187,14 +191,14 @@ static int tcp_write_timeout(struct sock *sk)
 
                         retry_until = tcp_orphan_retries(sk, alive);
                         do_reset = alive ||
-                                   !retransmits_timed_out(sk, retry_until);
+                                   !retransmits_timed_out(sk, retry_until, 0);
 
                         if (tcp_out_of_resources(sk, do_reset))
                                 return 1;
                 }
         }
 
-        if (retransmits_timed_out(sk, retry_until)) {
+        if (retransmits_timed_out(sk, retry_until, syn_set)) {
                 /* Has it gone just too far? */
                 tcp_write_err(sk);
                 return 1;
@@ -436,7 +440,7 @@ out_reset_timer:
                 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
         }
         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
-        if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
+        if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0))
                 __sk_dst_reset(sk);
 
 out:;