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[ISS#2319]fix(DU): Reducing synRetry count for faster connect calls (… #182

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merged 1 commit into from Jan 2, 2019
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[ISS#2319]fix(DU): Reducing synRetry count for faster connect calls (… #182

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18 changes: 18 additions & 0 deletions lib/libzrepl/mgmt_conn.c
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Expand Up @@ -31,6 +31,8 @@
#include <sys/socket.h>
#include <sys/eventfd.h>
#include <sys/prctl.h>
#include <netinet/in.h>
#include <netinet/tcp.h>

#include <sys/dsl_dataset.h>
#include <sys/dsl_destroy.h>
Expand Down Expand Up @@ -173,6 +175,7 @@ connect_to_tgt(uzfs_mgmt_conn_t *conn)
{
struct sockaddr_in istgt_addr;
int sfd, rc;
int synretries = 3;

conn->conn_last_connect = time(NULL);

Expand All @@ -185,6 +188,21 @@ connect_to_tgt(uzfs_mgmt_conn_t *conn)
if (sfd < 0)
return (-1);

/*
* synretry count is usually 6, which takes > 2 minutes.
* kernel retries syn at 1, 2, 4, 8, 16, 32 and 64 seconds.
* Due to some reason, even if listener at tgt is available,
* until these retransmissions are complete and start new connect
* call, connection is not getting established, and this is causing
* volume to get into RO state.
* By reducing synretries to 3, next connect call is made in less
* than 20 seconds.
*/
if (setsockopt(sfd, IPPROTO_TCP, TCP_SYNCNT, &synretries,
sizeof (int)) < 0) {
perror("setsockopt(TCP_SYNCNT) failed");
}

rc = connect(sfd, (struct sockaddr *)&istgt_addr, sizeof (istgt_addr));
/* EINPROGRESS means that EPOLLOUT will tell us when connect is done */
if (rc != 0 && errno != EINPROGRESS) {
Expand Down