The following commit has been merged in the linux branch: commit b103cf34382f26ff48a87931b83f13b177b47c1a Author: Julian Anastasov ja@ssi.bg Date: Mon Oct 19 10:10:40 2009 +0000

tcp: fix TCP_DEFER_ACCEPT retrans calculation

Fix TCP_DEFER_ACCEPT conversion between seconds and retransmission to match the TCP SYN-ACK retransmission periods because the time is converted to such retransmissions. The old algorithm selects one more retransmission in some cases. Allow up to 255 retransmissions.

Signed-off-by: Julian Anastasov ja@ssi.bg Acked-by: Eric Dumazet eric.dumazet@gmail.com Signed-off-by: David S. Miller davem@davemloft.net

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 64d0af6..9b2756f 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -326,6 +326,43 @@ void tcp_enter_memory_pressure(struct sock *sk)

EXPORT_SYMBOL(tcp_enter_memory_pressure);

+/* Convert seconds to retransmits based on initial and max timeout */ +static u8 secs_to_retrans(int seconds, int timeout, int rto_max) +{ + u8 res = 0; + + if (seconds > 0) { + int period = timeout; + + res = 1; + while (seconds > period && res < 255) { + res++; + timeout <<= 1; + if (timeout > rto_max) + timeout = rto_max; + period += timeout; + } + } + return res; +} + +/* Convert retransmits to seconds based on initial and max timeout */ +static int retrans_to_secs(u8 retrans, int timeout, int rto_max) +{ + int period = 0; + + if (retrans > 0) { + period = timeout; + while (--retrans) { + timeout <<= 1; + if (timeout > rto_max) + timeout = rto_max; + period += timeout; + } + } + return period; +} + /* * Wait for a TCP event. * @@ -2163,16 +2200,10 @@ static int do_tcp_setsockopt(struct sock *sk, int level, break;

case TCP_DEFER_ACCEPT: - icsk->icsk_accept_queue.rskq_defer_accept = 0; - if (val > 0) { - /* Translate value in seconds to number of - * retransmits */ - while (icsk->icsk_accept_queue.rskq_defer_accept < 32 && - val > ((TCP_TIMEOUT_INIT / HZ) << - icsk->icsk_accept_queue.rskq_defer_accept)) - icsk->icsk_accept_queue.rskq_defer_accept++; - icsk->icsk_accept_queue.rskq_defer_accept++; - } + /* Translate value in seconds to number of retransmits */ + icsk->icsk_accept_queue.rskq_defer_accept = + secs_to_retrans(val, TCP_TIMEOUT_INIT / HZ, + TCP_RTO_MAX / HZ); break;

case TCP_WINDOW_CLAMP: @@ -2353,8 +2384,8 @@ static int do_tcp_getsockopt(struct sock *sk, int level, val = (val ? : sysctl_tcp_fin_timeout) / HZ; break; case TCP_DEFER_ACCEPT: - val = !icsk->icsk_accept_queue.rskq_defer_accept ? 0 : - ((TCP_TIMEOUT_INIT / HZ) << (icsk->icsk_accept_queue.rskq_defer_accept - 1)); + val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept, + TCP_TIMEOUT_INIT / HZ, TCP_RTO_MAX / HZ); break; case TCP_WINDOW_CLAMP: val = tp->window_clamp;