ipv4: Create probe timer for tcp PMTU as per RFC4821
As per RFC4821 7.3. Selecting Probe Size, a probe timer should
be armed once probing has converged. Once this timer expired,
probing again to take advantage of any path PMTU change. The
recommended probing interval is 10 minutes per RFC1981. Probing
interval could be sysctled by sysctl_tcp_probe_interval.
Eric Dumazet suggested to implement pseudo timer based on 32bits
jiffies tcp_time_stamp instead of using classic timer for such
rare event.
Signed-off-by: Fan Du <fan.du@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index d3c09c1..fdf8991 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -890,6 +890,13 @@
.mode = 0644,
.proc_handler = proc_dointvec,
},
+ {
+ .procname = "tcp_probe_interval",
+ .data = &init_net.ipv4.sysctl_tcp_probe_interval,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
{ }
};
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 35790d9..f0c6fc3 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2461,6 +2461,7 @@
net->ipv4.sysctl_tcp_ecn = 2;
net->ipv4.sysctl_tcp_base_mss = TCP_BASE_MSS;
net->ipv4.sysctl_tcp_probe_threshold = TCP_PROBE_THRESHOLD;
+ net->ipv4.sysctl_tcp_probe_interval = TCP_PROBE_INTERVAL;
return 0;
fail:
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ed024cb..5a73ad5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1354,6 +1354,8 @@
icsk->icsk_af_ops->net_header_len;
icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
icsk->icsk_mtup.probe_size = 0;
+ if (icsk->icsk_mtup.enabled)
+ icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
}
EXPORT_SYMBOL(tcp_mtup_init);
@@ -1828,6 +1830,31 @@
return false;
}
+static inline void tcp_mtu_check_reprobe(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct net *net = sock_net(sk);
+ u32 interval;
+ s32 delta;
+
+ interval = net->ipv4.sysctl_tcp_probe_interval;
+ delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp;
+ if (unlikely(delta >= interval * HZ)) {
+ int mss = tcp_current_mss(sk);
+
+ /* Update current search range */
+ icsk->icsk_mtup.probe_size = 0;
+ icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
+ sizeof(struct tcphdr) +
+ icsk->icsk_af_ops->net_header_len;
+ icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
+
+ /* Update probe time stamp */
+ icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
+ }
+}
+
/* Create a new MTU probe if we are ready.
* MTU probe is regularly attempting to increase the path MTU by
* deliberately sending larger packets. This discovers routing
@@ -1870,9 +1897,16 @@
icsk->icsk_mtup.search_low) >> 1);
size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
+ /* When misfortune happens, we are reprobing actively,
+ * and then reprobe timer has expired. We stick with current
+ * probing process by not resetting search range to its orignal.
+ */
if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
- interval < max(1, net->ipv4.sysctl_tcp_probe_threshold)) {
- /* TODO: set timer for probe_converge_event */
+ interval < net->ipv4.sysctl_tcp_probe_threshold) {
+ /* Check whether enough time has elaplased for
+ * another round of probing.
+ */
+ tcp_mtu_check_reprobe(sk);
return -1;
}
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 0732b78..1550593 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -107,6 +107,7 @@
if (net->ipv4.sysctl_tcp_mtu_probing) {
if (!icsk->icsk_mtup.enabled) {
icsk->icsk_mtup.enabled = 1;
+ icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
} else {
struct net *net = sock_net(sk);