diff options
| author | John Heffner <jheffner@psc.edu> | 2006-03-20 17:53:41 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2006-03-20 17:53:41 -0800 |
| commit | 5d424d5a674f782d0659a3b66d951f412901faee (patch) | |
| tree | 579871172044e02e626a90388d19ec55cf2d1fc4 /net/ipv4/tcp_timer.c | |
| parent | 1d60290f27e7dc4bce2c43922d0bfa9abd246fc9 (diff) | |
| download | lwn-5d424d5a674f782d0659a3b66d951f412901faee.tar.gz lwn-5d424d5a674f782d0659a3b66d951f412901faee.zip | |
[TCP]: MTU probing
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>
Diffstat (limited to 'net/ipv4/tcp_timer.c')
| -rw-r--r-- | net/ipv4/tcp_timer.c | 36 |
1 files changed, 16 insertions, 20 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index e1880959614a..7c1bde3cd6cb 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -119,8 +119,10 @@ static int tcp_orphan_retries(struct sock *sk, int alive) /* A write timeout has occurred. Process the after effects. */ static int tcp_write_timeout(struct sock *sk) { - const struct inet_connection_sock *icsk = inet_csk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); int retry_until; + int mss; if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { if (icsk->icsk_retransmits) @@ -128,25 +130,19 @@ static int tcp_write_timeout(struct sock *sk) retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries; } else { if (icsk->icsk_retransmits >= sysctl_tcp_retries1) { - /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu black - hole detection. :-( - - It is place to make it. It is not made. I do not want - to make it. It is disgusting. It does not work in any - case. Let me to cite the same draft, which requires for - us to implement this: - - "The one security concern raised by this memo is that ICMP black holes - are often caused by over-zealous security administrators who block - all ICMP messages. It is vitally important that those who design and - deploy security systems understand the impact of strict filtering on - upper-layer protocols. The safest web site in the world is worthless - if most TCP implementations cannot transfer data from it. It would - be far nicer to have all of the black holes fixed rather than fixing - all of the TCP implementations." - - Golden words :-). - */ + /* Black hole detection */ + if (sysctl_tcp_mtu_probing) { + if (!icsk->icsk_mtup.enabled) { + icsk->icsk_mtup.enabled = 1; + tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); + } else { + mss = min(sysctl_tcp_base_mss, + tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)/2); + mss = max(mss, 68 - tp->tcp_header_len); + icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); + tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); + } + } dst_negative_advice(&sk->sk_dst_cache); } |