Commit 83d0585f authored by Jakub Kicinski's avatar Jakub Kicinski

Merge branch 'Fix-reconnection-latency-caused-by-FIN-ACK-handling-race'

SeongJae Park says:

====================
Fix reconnection latency caused by FIN/ACK handling race

The first patch fixes the problem by adjusting the first resend delay of
the SYN in the case.  The second one adds a user space test to reproduce
this problem.

From v2
(https://lore.kernel.org/linux-kselftest/20200201071859.4231-1-sj38.park@gmail.com/)
 - Use TCP_TIMEOUT_MIN as reduced delay (Neal Cardwall)
 - Add Reviewed-by and Signed-off-by from Eric Dumazet

From v1
(https://lore.kernel.org/linux-kselftest/20200131122421.23286-1-sjpark@amazon.com/)
 - Drop the trivial comment fix patch (Eric Dumazet)
 - Limit the delay adjustment to only the first SYN resend (Eric Dumazet)
 - selftest: Avoid use of hard-coded port number (Eric Dumazet)
 - Explain RST/ACK and FIN/ACK has no big difference (Neal Cardwell)
====================
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parents dff6bc1b af8c8a45
...@@ -5908,8 +5908,14 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, ...@@ -5908,8 +5908,14 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
* the segment and return)" * the segment and return)"
*/ */
if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) || if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
/* Previous FIN/ACK or RST/ACK might be ignored. */
if (icsk->icsk_retransmits == 0)
inet_csk_reset_xmit_timer(sk,
ICSK_TIME_RETRANS,
TCP_TIMEOUT_MIN, TCP_RTO_MAX);
goto reset_and_undo; goto reset_and_undo;
}
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
!between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
......
...@@ -22,3 +22,4 @@ ipv6_flowlabel_mgr ...@@ -22,3 +22,4 @@ ipv6_flowlabel_mgr
so_txtime so_txtime
tcp_fastopen_backup_key tcp_fastopen_backup_key
nettest nettest
fin_ack_lat
...@@ -11,6 +11,7 @@ TEST_PROGS += udpgso_bench.sh fib_rule_tests.sh msg_zerocopy.sh psock_snd.sh ...@@ -11,6 +11,7 @@ TEST_PROGS += udpgso_bench.sh fib_rule_tests.sh msg_zerocopy.sh psock_snd.sh
TEST_PROGS += udpgro_bench.sh udpgro.sh test_vxlan_under_vrf.sh reuseport_addr_any.sh TEST_PROGS += udpgro_bench.sh udpgro.sh test_vxlan_under_vrf.sh reuseport_addr_any.sh
TEST_PROGS += test_vxlan_fdb_changelink.sh so_txtime.sh ipv6_flowlabel.sh TEST_PROGS += test_vxlan_fdb_changelink.sh so_txtime.sh ipv6_flowlabel.sh
TEST_PROGS += tcp_fastopen_backup_key.sh fcnal-test.sh l2tp.sh traceroute.sh TEST_PROGS += tcp_fastopen_backup_key.sh fcnal-test.sh l2tp.sh traceroute.sh
TEST_PROGS += fin_ack_lat.sh
TEST_PROGS_EXTENDED := in_netns.sh TEST_PROGS_EXTENDED := in_netns.sh
TEST_GEN_FILES = socket nettest TEST_GEN_FILES = socket nettest
TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy reuseport_addr_any TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy reuseport_addr_any
...@@ -18,6 +19,7 @@ TEST_GEN_FILES += tcp_mmap tcp_inq psock_snd txring_overwrite ...@@ -18,6 +19,7 @@ TEST_GEN_FILES += tcp_mmap tcp_inq psock_snd txring_overwrite
TEST_GEN_FILES += udpgso udpgso_bench_tx udpgso_bench_rx ip_defrag TEST_GEN_FILES += udpgso udpgso_bench_tx udpgso_bench_rx ip_defrag
TEST_GEN_FILES += so_txtime ipv6_flowlabel ipv6_flowlabel_mgr TEST_GEN_FILES += so_txtime ipv6_flowlabel ipv6_flowlabel_mgr
TEST_GEN_FILES += tcp_fastopen_backup_key TEST_GEN_FILES += tcp_fastopen_backup_key
TEST_GEN_FILES += fin_ack_lat
TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
TEST_GEN_PROGS += reuseport_dualstack reuseaddr_conflict tls TEST_GEN_PROGS += reuseport_dualstack reuseaddr_conflict tls
......
// SPDX-License-Identifier: GPL-2.0
#include <arpa/inet.h>
#include <errno.h>
#include <error.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <unistd.h>
static int child_pid;
static unsigned long timediff(struct timeval s, struct timeval e)
{
unsigned long s_us, e_us;
s_us = s.tv_sec * 1000000 + s.tv_usec;
e_us = e.tv_sec * 1000000 + e.tv_usec;
if (s_us > e_us)
return 0;
return e_us - s_us;
}
static void client(int port)
{
int sock = 0;
struct sockaddr_in addr, laddr;
socklen_t len = sizeof(laddr);
struct linger sl;
int flag = 1;
int buffer;
struct timeval start, end;
unsigned long lat, sum_lat = 0, nr_lat = 0;
while (1) {
gettimeofday(&start, NULL);
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0)
error(-1, errno, "socket creation");
sl.l_onoff = 1;
sl.l_linger = 0;
if (setsockopt(sock, SOL_SOCKET, SO_LINGER, &sl, sizeof(sl)))
error(-1, errno, "setsockopt(linger)");
if (setsockopt(sock, IPPROTO_TCP, TCP_NODELAY,
&flag, sizeof(flag)))
error(-1, errno, "setsockopt(nodelay)");
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
if (inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr) <= 0)
error(-1, errno, "inet_pton");
if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0)
error(-1, errno, "connect");
send(sock, &buffer, sizeof(buffer), 0);
if (read(sock, &buffer, sizeof(buffer)) == -1)
error(-1, errno, "waiting read");
gettimeofday(&end, NULL);
lat = timediff(start, end);
sum_lat += lat;
nr_lat++;
if (lat < 100000)
goto close;
if (getsockname(sock, (struct sockaddr *)&laddr, &len) == -1)
error(-1, errno, "getsockname");
printf("port: %d, lat: %lu, avg: %lu, nr: %lu\n",
ntohs(laddr.sin_port), lat,
sum_lat / nr_lat, nr_lat);
close:
fflush(stdout);
close(sock);
}
}
static void server(int sock, struct sockaddr_in address)
{
int accepted;
int addrlen = sizeof(address);
int buffer;
while (1) {
accepted = accept(sock, (struct sockaddr *)&address,
(socklen_t *)&addrlen);
if (accepted < 0)
error(-1, errno, "accept");
if (read(accepted, &buffer, sizeof(buffer)) == -1)
error(-1, errno, "read");
close(accepted);
}
}
static void sig_handler(int signum)
{
kill(SIGTERM, child_pid);
exit(0);
}
int main(int argc, char const *argv[])
{
int sock;
int opt = 1;
struct sockaddr_in address;
struct sockaddr_in laddr;
socklen_t len = sizeof(laddr);
if (signal(SIGTERM, sig_handler) == SIG_ERR)
error(-1, errno, "signal");
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0)
error(-1, errno, "socket");
if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT,
&opt, sizeof(opt)) == -1)
error(-1, errno, "setsockopt");
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
/* dynamically allocate unused port */
address.sin_port = 0;
if (bind(sock, (struct sockaddr *)&address, sizeof(address)) < 0)
error(-1, errno, "bind");
if (listen(sock, 3) < 0)
error(-1, errno, "listen");
if (getsockname(sock, (struct sockaddr *)&laddr, &len) == -1)
error(-1, errno, "getsockname");
fprintf(stderr, "server port: %d\n", ntohs(laddr.sin_port));
child_pid = fork();
if (!child_pid)
client(ntohs(laddr.sin_port));
else
server(sock, laddr);
return 0;
}
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
#
# Test latency spikes caused by FIN/ACK handling race.
set +x
set -e
tmpfile=$(mktemp /tmp/fin_ack_latency.XXXX.log)
cleanup() {
kill $(pidof fin_ack_lat)
rm -f $tmpfile
}
trap cleanup EXIT
do_test() {
RUNTIME=$1
./fin_ack_lat | tee $tmpfile &
PID=$!
sleep $RUNTIME
NR_SPIKES=$(wc -l $tmpfile | awk '{print $1}')
if [ $NR_SPIKES -gt 0 ]
then
echo "FAIL: $NR_SPIKES spikes detected"
return 1
fi
return 0
}
do_test "30"
echo "test done"
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