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[TCP]: MTU probing

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Implementation of packetization layer path mtu discovery for TCP, based on
the internet-draft currently found at
<http://www.ietf.org/internet-drafts/draft-ietf-pmtud-method-05.txt>.

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Heffner
2006-03-20 17:53:41 -08:00
committed by David S. Miller
parent 1d60290f27
commit 5d424d5a67
9 changed files with 326 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

49
net/ipv4/tcp_input.c
View File

@@ -1891,6 +1891,34 @@ static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
}
}
static void tcp_mtup_probe_failed(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
icsk->icsk_mtup.probe_size = 0;
}
static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
{
struct tcp_sock *tp = tcp_sk(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
/* FIXME: breaks with very large cwnd */
tp->prior_ssthresh = tcp_current_ssthresh(sk);
tp->snd_cwnd = tp->snd_cwnd *
tcp_mss_to_mtu(sk, tp->mss_cache) /
icsk->icsk_mtup.probe_size;
tp->snd_cwnd_cnt = 0;
tp->snd_cwnd_stamp = tcp_time_stamp;
tp->rcv_ssthresh = tcp_current_ssthresh(sk);
icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
icsk->icsk_mtup.probe_size = 0;
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
}
/* Process an event, which can update packets-in-flight not trivially.
* Main goal of this function is to calculate new estimate for left_out,
* taking into account both packets sitting in receiver's buffer and
@@ -2023,6 +2051,17 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
return;
}
/* MTU probe failure: don't reduce cwnd */
if (icsk->icsk_ca_state < TCP_CA_CWR &&
icsk->icsk_mtup.probe_size &&
tp->snd_una == icsk->icsk_mtup.probe_seq_start) {
tcp_mtup_probe_failed(sk);
/* Restores the reduction we did in tcp_mtup_probe() */
tp->snd_cwnd++;
tcp_simple_retransmit(sk);
return;
}
/* Otherwise enter Recovery state */
if (IsReno(tp))
@@ -2243,6 +2282,13 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
tp->retrans_stamp = 0;
}
/* MTU probing checks */
if (icsk->icsk_mtup.probe_size) {
if (!after(icsk->icsk_mtup.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) {
tcp_mtup_probe_success(sk, skb);
}
}
if (sacked) {
if (sacked & TCPCB_RETRANS) {
if(sacked & TCPCB_SACKED_RETRANS)
@@ -4101,6 +4147,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
tp->rx_opt.sack_ok |= 2;
tcp_mtup_init(sk);
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
tcp_initialize_rcv_mss(sk);
@@ -4211,6 +4258,7 @@ discard:
if (tp->ecn_flags&TCP_ECN_OK)
sock_set_flag(sk, SOCK_NO_LARGESEND);
tcp_mtup_init(sk);
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
tcp_initialize_rcv_mss(sk);
@@ -4399,6 +4447,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
*/
tp->lsndtime = tcp_time_stamp;
tcp_mtup_init(sk);
tcp_initialize_rcv_mss(sk);
tcp_init_buffer_space(sk);
tcp_fast_path_on(tp);