[Dnsmasq-discuss] listen-backlog option to override default (too small) value

Discussion:

Donatas Abraitis

2016-12-07 12:43:22 UTC

Hi folks,

for our case at Hostinger, we have a problem while too much
TcpListenOverflows:
[***@us-imm-dns1 ~]# nstat -az | grep TcpExtListenOverflows
TcpExtListenOverflows 299 0.0
[***@us-imm-dns1 ~]# ss -ntl sport = :53
State Recv-Q Send-Q Local
Address:Port Peer
Address:Port
LISTEN 0
5
*:53
*:*
LISTEN 0
5
:::53
:::*

probe kernel.function("tcp_check_req")
{
tcphdr = __get_skb_tcphdr($skb);
dport = __tcp_skb_dport(tcphdr)
if ($sk->sk_ack_backlog > $sk->sk_max_ack_backlog)
printf("listen queue for port(%d): %d/%d\n",
dport,
$sk->sk_ack_backlog,
$sk->sk_max_ack_backlog);
}

[***@us-imm-dns1 ~]# staprun overflow.ko
listen queue for port(53): 13/5
listen queue for port(53): 13/5
listen queue for port(53): 14/5

here is the proposed patch:

commit fa610cd424b905720832afc8636373bb132f49c1
Author: Donatas Abraitis <***@gmail.com>
Date: Sun Dec 9 09:58:51 2012 +0200

Add `listen-backlog` option to override default 5 (too small)

diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 4b55bb5..b717df3 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -980,6 +980,7 @@ extern struct daemon {
struct dhcp_netid_list *force_broadcast, *bootp_dynamic;
struct hostsfile *dhcp_hosts_file, *dhcp_opts_file, *dynamic_dirs;
int dhcp_max, tftp_max, tftp_mtu;
+ int listen_backlog;
int dhcp_server_port, dhcp_client_port;
int start_tftp_port, end_tftp_port;
unsigned int min_leasetime;
diff --git a/src/network.c b/src/network.c
index d87d08f..1e9d188 100644
--- a/src/network.c
+++ b/src/network.c
@@ -746,7 +746,7 @@ static int make_sock(union mysockaddr *addr, int type,
int dienow)

if (type == SOCK_STREAM)
{
- if (listen(fd, 5) == -1)
+ if (listen(fd, daemon->listen_backlog) == -1)
goto err;
}
else if (family == AF_INET)
diff --git a/src/option.c b/src/option.c
index d0d9509..220303e 100644
--- a/src/option.c
+++ b/src/option.c
@@ -159,6 +159,7 @@ struct myoption {
#define LOPT_SCRIPT_ARP 347
#define LOPT_DHCPTTL 348
#define LOPT_TFTP_MTU 349
+#define LOPT_BACKLOG 350

#ifdef HAVE_GETOPT_LONG
static const struct option opts[] =
@@ -190,6 +191,7 @@ static const struct myoption opts[] =
{ "domain-suffix", 1, 0, 's' },
{ "interface", 1, 0, 'i' },
{ "listen-address", 1, 0, 'a' },
+ { "listen-backlog", 1, 0, LOPT_BACKLOG },
{ "local-service", 0, 0, LOPT_LOCAL_SERVICE },
{ "bogus-priv", 0, 0, 'b' },
{ "bogus-nxdomain", 1, 0, 'B' },
@@ -394,6 +396,7 @@ static struct {
{ 't', ARG_ONE, "<host_name>", gettext_noop("Specify default target in
an MX record."), NULL },
{ 'T', ARG_ONE, "<integer>", gettext_noop("Specify time-to-live in
seconds for replies from /etc/hosts."), NULL },
{ LOPT_NEGTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live
in seconds for negative caching."), NULL },
+ { LOPT_BACKLOG, ARG_ONE, "<integer>", gettext_noop("Set the backlog
queue limit."), NULL },
{ LOPT_MAXTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live
in seconds for maximum TTL to send to clients."), NULL },
{ LOPT_MAXCTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live
ceiling for cache."), NULL },
{ LOPT_MINCTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live
floor for cache."), NULL },
@@ -2286,7 +2289,11 @@ static int one_opt(int option, char *arg, char
*errstr, char *gen_err, int comma
ret_err(gen_err); /* error */
break;
}
-
+
+ case LOPT_BACKLOG: /* --listen-backlog */
+ if (!atoi_check(arg, &daemon->listen_backlog))
+ ret_err(gen_err);
+ break;
case 'a': /* --listen-address */
case LOPT_AUTHPEER: /* --auth-peer */
do {
@@ -4517,6 +4524,7 @@ void read_opts(int argc, char **argv, char
*compile_opts)
daemon->cachesize = CACHESIZ;
daemon->ftabsize = FTABSIZ;
daemon->port = NAMESERVER_PORT;
+ daemon->listen_backlog = 5;
daemon->dhcp_client_port = DHCP_CLIENT_PORT;
daemon->dhcp_server_port = DHCP_SERVER_PORT;
daemon->default_resolv.is_default = 1;

--
Donatas

Albert ARIBAUD

2016-12-07 13:28:22 UTC

Permalink

Hi Donatas,

Le Wed, 7 Dec 2016 14:43:22 +0200

Post by Donatas Abraitis
Hi folks,
for our case at Hostinger, we have a problem while too much
TcpExtListenOverflows 299 0.0
State Recv-Q Send-Q
Local
Address:Port
Peer Address:Port LISTEN 0
5
*:53
*:*
LISTEN 0
5
:::53
:::*
probe kernel.function("tcp_check_req")
{
tcphdr = __get_skb_tcphdr($skb);
dport = __tcp_skb_dport(tcphdr)
if ($sk->sk_ack_backlog > $sk->sk_max_ack_backlog)
printf("listen queue for port(%d): %d/%d\n",
dport,
$sk->sk_ack_backlog,
$sk->sk_max_ack_backlog);
}
listen queue for port(53): 13/5
listen queue for port(53): 13/5
listen queue for port(53): 14/5
commit fa610cd424b905720832afc8636373bb132f49c1
Date: Sun Dec 9 09:58:51 2012 +0200
Add `listen-backlog` option to override default 5 (too small)
diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 4b55bb5..b717df3 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -980,6 +980,7 @@ extern struct daemon {
struct dhcp_netid_list *force_broadcast, *bootp_dynamic;
struct hostsfile *dhcp_hosts_file, *dhcp_opts_file, *dynamic_dirs;
int dhcp_max, tftp_max, tftp_mtu;
+ int listen_backlog;
int dhcp_server_port, dhcp_client_port;
int start_tftp_port, end_tftp_port;
unsigned int min_leasetime;
diff --git a/src/network.c b/src/network.c
index d87d08f..1e9d188 100644
--- a/src/network.c
+++ b/src/network.c
@@ -746,7 +746,7 @@ static int make_sock(union mysockaddr *addr, int
type, int dienow)
if (type == SOCK_STREAM)
{
- if (listen(fd, 5) == -1)
+ if (listen(fd, daemon->listen_backlog) == -1)
goto err;
}
else if (family == AF_INET)
diff --git a/src/option.c b/src/option.c
index d0d9509..220303e 100644
--- a/src/option.c
+++ b/src/option.c
@@ -159,6 +159,7 @@ struct myoption {
#define LOPT_SCRIPT_ARP 347
#define LOPT_DHCPTTL 348
#define LOPT_TFTP_MTU 349
+#define LOPT_BACKLOG 350
#ifdef HAVE_GETOPT_LONG
static const struct option opts[] =
@@ -190,6 +191,7 @@ static const struct myoption opts[] =
{ "domain-suffix", 1, 0, 's' },
{ "interface", 1, 0, 'i' },
{ "listen-address", 1, 0, 'a' },
+ { "listen-backlog", 1, 0, LOPT_BACKLOG },
{ "local-service", 0, 0, LOPT_LOCAL_SERVICE },
{ "bogus-priv", 0, 0, 'b' },
{ "bogus-nxdomain", 1, 0, 'B' },
@@ -394,6 +396,7 @@ static struct {
{ 't', ARG_ONE, "<host_name>", gettext_noop("Specify default
target in an MX record."), NULL },
{ 'T', ARG_ONE, "<integer>", gettext_noop("Specify time-to-live in
seconds for replies from /etc/hosts."), NULL },
{ LOPT_NEGTTL, ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live in seconds for negative caching."), NULL },
+ { LOPT_BACKLOG, ARG_ONE, "<integer>", gettext_noop("Set the backlog
queue limit."), NULL },
{ LOPT_MAXTTL, ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live in seconds for maximum TTL to send to clients."), NULL },
{ LOPT_MAXCTTL, ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live ceiling for cache."), NULL },
{ LOPT_MINCTTL, ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live floor for cache."), NULL },
@@ -2286,7 +2289,11 @@ static int one_opt(int option, char *arg, char
*errstr, char *gen_err, int comma
ret_err(gen_err); /* error */
break;
}
-
+
+ case LOPT_BACKLOG: /* --listen-backlog */
+ if (!atoi_check(arg, &daemon->listen_backlog))
+ ret_err(gen_err);
+ break;
case 'a': /* --listen-address */
case LOPT_AUTHPEER: /* --auth-peer */
do {
@@ -4517,6 +4524,7 @@ void read_opts(int argc, char **argv, char
*compile_opts)
daemon->cachesize = CACHESIZ;
daemon->ftabsize = FTABSIZ;
daemon->port = NAMESERVER_PORT;
+ daemon->listen_backlog = 5;
daemon->dhcp_client_port = DHCP_CLIENT_PORT;
daemon->dhcp_server_port = DHCP_SERVER_PORT;
daemon->default_resolv.is_default = 1;

I am not qualified to determine if your patch is the right solution to
your problem, but FWIW, I find this patch clear enough and I assume you
have tested it :) and that it actually solves the issue for you. The
only two remarks I have are:

- it would be nice to also add a description for the option
and its rationale to the manpage;

- is there a way for dnsmasq to detect excessive backlog and emit a
diagnostic message pointing the operator to the existence and use of
the listen-backlog option, and if so, could you add this to the patch?

Note that I am in no way a maintainer of dnsmasq, so neither my review
nor my questions should be mistaken for an acceptation of the patch --
only Simon can accept patches.

Amicalement,

--
Albert.

Donatas Abraitis

2016-12-07 13:43:53 UTC

Permalink

Of course patch is tested ;-)
Some output:
% ./src/dnsmasq --port 1025 --listen-backlog 100
% ss -ntl sport = :1025
Recv-Q Send-Q
Local
Address:Port
Peer Address:Port
0
100
:::1025
:::*
0
100
*:1025

Post by Albert ARIBAUD
Hi Donatas,
Le Wed, 7 Dec 2016 14:43:22 +0200

I am not qualified to determine if your patch is the right solution to
your problem, but FWIW, I find this patch clear enough and I assume you
have tested it :) and that it actually solves the issue for you. The
- it would be nice to also add a description for the option
and its rationale to the manpage;
- is there a way for dnsmasq to detect excessive backlog and emit a
diagnostic message pointing the operator to the existence and use of
the listen-backlog option, and if so, could you add this to the patch?
Note that I am in no way a maintainer of dnsmasq, so neither my review
nor my questions should be mistaken for an acceptation of the patch --
only Simon can accept patches.
Amicalement,
--
Albert.

--
Donatas

Simon Kelley

2016-12-16 16:43:05 UTC

Permalink

What backlog parameter works well for you?

I'm happy to apply the patch if this is a dial that really needs to be
tweakable, but if there are no downsides to moving the fixed backlog
limit from 5 to 50 or 500, then let's just do that. There's no point
in making people apply arbitrary configuration options if it can just
work.

Cheers,

Simon.

Of course patch is tested ;-) Some output: % ./src/dnsmasq --port
1025 --listen-backlog 100 % ss -ntl sport = :1025 Recv-Q Send-Q
Local Address:Port Peer Address:Port 0 100 :::1025 :::* 0 100
*:1025
On Wed, Dec 7, 2016 at 3:28 PM, Albert ARIBAUD

Post by Albert ARIBAUD
Hi Donatas,
Le Wed, 7 Dec 2016 14:43:22 +0200 Donatas Abraitis

Post by Donatas Abraitis
Hi folks,
for our case at Hostinger, we have a problem while too much
TcpExtListenOverflows TcpExtListenOverflows 299
Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN
0 5 *:53 *:* LISTEN 0 5 :::53 :::*
probe kernel.function("tcp_check_req") { tcphdr =
__get_skb_tcphdr($skb); dport = __tcp_skb_dport(tcphdr) if
($sk->sk_ack_backlog > $sk->sk_max_ack_backlog) printf("listen
queue for port(%d): %d/%d\n", dport, $sk->sk_ack_backlog,
$sk->sk_max_ack_backlog); }
port(53): 13/5 listen queue for port(53): 13/5 listen queue for
port(53): 14/5
commit fa610cd424b905720832afc8636373bb132f49c1 Author: Donatas
09:58:51 2012 +0200
Add `listen-backlog` option to override default 5 (too small)
diff --git a/src/dnsmasq.h b/src/dnsmasq.h index
4b55bb5..b717df3 100644 --- a/src/dnsmasq.h +++
struct dhcp_netid_list *force_broadcast, *bootp_dynamic; struct
hostsfile *dhcp_hosts_file, *dhcp_opts_file, *dynamic_dirs; int
dhcp_max, tftp_max, tftp_mtu; + int listen_backlog; int
dhcp_server_port, dhcp_client_port; int start_tftp_port,
end_tftp_port; unsigned int min_leasetime; diff --git
a/src/network.c b/src/network.c index d87d08f..1e9d188 100644
static int make_sock(union mysockaddr *addr, int type, int
dienow)
if (type == SOCK_STREAM) { - if (listen(fd, 5) == -1) +
if (listen(fd, daemon->listen_backlog) == -1) goto err; } else
if (family == AF_INET) diff --git a/src/option.c
b/src/option.c index d0d9509..220303e 100644 ---
myoption { #define LOPT_SCRIPT_ARP 347 #define LOPT_DHCPTTL
348 #define LOPT_TFTP_MTU 349 +#define LOPT_BACKLOG
350
"domain-suffix", 1, 0, 's' }, { "interface", 1, 0, 'i' }, {
"listen-address", 1, 0, 'a' }, + { "listen-backlog", 1, 0,
LOPT_BACKLOG }, { "local-service", 0, 0, LOPT_LOCAL_SERVICE },
{ "bogus-priv", 0, 0, 'b' }, { "bogus-nxdomain", 1, 0, 'B' },
@@ -394,6 +396,7 @@ static struct { { 't', ARG_ONE,
"<host_name>", gettext_noop("Specify default target in an MX
record."), NULL }, { 'T', ARG_ONE, "<integer>",
gettext_noop("Specify time-to-live in seconds for replies from
/etc/hosts."), NULL }, { LOPT_NEGTTL, ARG_ONE, "<integer>",
gettext_noop("Specify time-to-live in seconds for negative
caching."), NULL }, + { LOPT_BACKLOG, ARG_ONE, "<integer>",
gettext_noop("Set the backlog queue limit."), NULL }, {
LOPT_MAXTTL, ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live in seconds for maximum TTL to send to clients."),
NULL }, { LOPT_MAXCTTL, ARG_ONE, "<integer>",
gettext_noop("Specify time-to-live ceiling for cache."), NULL
}, { LOPT_MINCTTL, ARG_ONE, "<integer>", gettext_noop("Specify
static int one_opt(int option, char *arg, char *errstr, char
*gen_err, int comma ret_err(gen_err); /* error */ break; } - +
+ case LOPT_BACKLOG: /* --listen-backlog */ + if
(!atoi_check(arg, &daemon->listen_backlog)) +
ret_err(gen_err); + break; case 'a': /* --listen-address
*compile_opts) daemon->cachesize = CACHESIZ; daemon->ftabsize =
FTABSIZ; daemon->port = NAMESERVER_PORT; +
daemon->listen_backlog = 5; daemon->dhcp_client_port =
DHCP_CLIENT_PORT; daemon->dhcp_server_port = DHCP_SERVER_PORT;
daemon->default_resolv.is_default = 1;

I am not qualified to determine if your patch is the right
solution to your problem, but FWIW, I find this patch clear
enough and I assume you have tested it :) and that it actually
- it would be nice to also add a description for the option and
its rationale to the manpage;
- is there a way for dnsmasq to detect excessive backlog and emit
a diagnostic message pointing the operator to the existence and
use of the listen-backlog option, and if so, could you add this
to the patch?
Note that I am in no way a maintainer of dnsmasq, so neither my
review nor my questions should be mistaken for an acceptation of
the patch -- only Simon can accept patches.
Amicalement, -- Albert.

_______________________________________________ Dnsmasq-discuss
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Donatas Abraitis

2016-12-16 19:31:39 UTC

Permalink

Well, it depends, in our case it's enough 32, never hit this value still.

Sent from my iPhone

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
What backlog parameter works well for you?
I'm happy to apply the patch if this is a dial that really needs to be
tweakable, but if there are no downsides to moving the fixed backlog
limit from 5 to 50 or 500, then let's just do that. There's no point
in making people apply arbitrary configuration options if it can just
work.
Cheers,
Simon.

Post by Albert ARIBAUD
Hi Donatas,
Le Wed, 7 Dec 2016 14:43:22 +0200 Donatas Abraitis

_______________________________________________ Dnsmasq-discuss
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

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Simon Kelley

2016-12-19 11:48:10 UTC

Permalink

I think the simple solution to this is

1) Make this a compile-time option in /src/config.h
2) Bump the default to 50.

Does that sound reasonable?

Cheers,

Simon.

Post by Donatas Abraitis
Well, it depends, in our case it's enough 32, never hit this value still.
Sent from my iPhone
What backlog parameter works well for you?
I'm happy to apply the patch if this is a dial that really needs to
be tweakable, but if there are no downsides to moving the fixed
backlog limit from 5 to 50 or 500, then let's just do that. There's
no point in making people apply arbitrary configuration options if
it can just work.
Cheers,
Simon.

On 07/12/16 13:43, Donatas Abraitis wrote: Of course patch is
tested ;-) Some output: % ./src/dnsmasq --port 1025
--listen-backlog 100 % ss -ntl sport = :1025 Recv-Q Send-Q
Local Address:Port Peer Address:Port 0 100 :::1025 :::* 0 100
*:1025
On Wed, Dec 7, 2016 at 3:28 PM, Albert ARIBAUD

Post by Albert ARIBAUD
Hi Donatas,
Le Wed, 7 Dec 2016 14:43:22 +0200 Donatas Abraitis

Post by Donatas Abraitis
Hi folks,
for our case at Hostinger, we have a problem while too
| grep TcpExtListenOverflows TcpExtListenOverflows
Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 5 *:53 *:* LISTEN 0 5 :::53 :::*
probe kernel.function("tcp_check_req") { tcphdr =
__get_skb_tcphdr($skb); dport = __tcp_skb_dport(tcphdr)
if ($sk->sk_ack_backlog > $sk->sk_max_ack_backlog)
printf("listen queue for port(%d): %d/%d\n", dport,
$sk->sk_ack_backlog, $sk->sk_max_ack_backlog); }
for port(53): 13/5 listen queue for port(53): 13/5 listen
queue for port(53): 14/5
Dec 9 09:58:51 2012 +0200
Add `listen-backlog` option to override default 5 (too
small)
diff --git a/src/dnsmasq.h b/src/dnsmasq.h index
4b55bb5..b717df3 100644 --- a/src/dnsmasq.h +++
{ struct dhcp_netid_list *force_broadcast,
*bootp_dynamic; struct hostsfile *dhcp_hosts_file,
*dhcp_opts_file, *dynamic_dirs; int dhcp_max, tftp_max,
tftp_mtu; + int listen_backlog; int dhcp_server_port,
dhcp_client_port; int start_tftp_port, end_tftp_port;
unsigned int min_leasetime; diff --git a/src/network.c
b/src/network.c index d87d08f..1e9d188 100644 ---
static int make_sock(union mysockaddr *addr, int type,
int dienow)
if (type == SOCK_STREAM) { - if (listen(fd, 5) ==
-1) + if (listen(fd, daemon->listen_backlog) == -1) goto
err; } else if (family == AF_INET) diff --git
a/src/option.c b/src/option.c index d0d9509..220303e
347 #define LOPT_DHCPTTL 348 #define LOPT_TFTP_MTU
349 +#define LOPT_BACKLOG 350
#ifdef HAVE_GETOPT_LONG static const struct option opts[]
= { "domain-suffix", 1, 0, 's' }, { "interface", 1, 0,
'i' }, { "listen-address", 1, 0, 'a' }, + {
"listen-backlog", 1, 0, LOPT_BACKLOG }, {
"local-service", 0, 0, LOPT_LOCAL_SERVICE }, {
"bogus-priv", 0, 0, 'b' }, { "bogus-nxdomain", 1, 0, 'B'
"<host_name>", gettext_noop("Specify default target in an
MX record."), NULL }, { 'T', ARG_ONE, "<integer>",
gettext_noop("Specify time-to-live in seconds for replies
from /etc/hosts."), NULL }, { LOPT_NEGTTL, ARG_ONE,
"<integer>", gettext_noop("Specify time-to-live in
seconds for negative caching."), NULL }, + {
LOPT_BACKLOG, ARG_ONE, "<integer>", gettext_noop("Set the
backlog queue limit."), NULL }, { LOPT_MAXTTL, ARG_ONE,
"<integer>", gettext_noop("Specify time-to-live in
seconds for maximum TTL to send to clients."), NULL }, {
LOPT_MAXCTTL, ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live ceiling for cache."), NULL }, {
LOPT_MINCTTL, ARG_ONE, "<integer>", gettext_noop("Specify
char *errstr, char *gen_err, int comma ret_err(gen_err);
/* error */ break; } - + + case LOPT_BACKLOG: /*
--listen-backlog */ + if (!atoi_check(arg,
&daemon->listen_backlog)) + ret_err(gen_err); +
break; case 'a': /* --listen-address */ case
@@ void read_opts(int argc, char **argv, char
*compile_opts) daemon->cachesize = CACHESIZ;
daemon->ftabsize = FTABSIZ; daemon->port =
NAMESERVER_PORT; + daemon->listen_backlog = 5;
daemon->dhcp_client_port = DHCP_CLIENT_PORT;
daemon->dhcp_server_port = DHCP_SERVER_PORT;
daemon->default_resolv.is_default = 1;

I am not qualified to determine if your patch is the right
solution to your problem, but FWIW, I find this patch
clear enough and I assume you have tested it :) and that it
actually solves the issue for you. The only two remarks I
- it would be nice to also add a description for the option
and its rationale to the manpage;
- is there a way for dnsmasq to detect excessive backlog
and emit a diagnostic message pointing the operator to the
existence and use of the listen-backlog option, and if so,
could you add this to the patch?
Note that I am in no way a maintainer of dnsmasq, so
neither my review nor my questions should be mistaken for
an acceptation of the patch -- only Simon can accept
patches.
Amicalement, -- Albert.

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Post by Donatas Abraitis

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Simon Kelley

2016-12-22 22:39:45 UTC

Permalink

Done.

http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=09b768efa456fb
49f21e7ed19761ff24988464b9

Cheers,

Simon.

Post by Donatas Abraitis
Ok
Sent from my iPhone
I think the simple solution to this is
1) Make this a compile-time option in /src/config.h 2) Bump the
default to 50.
Does that sound reasonable?
Cheers,
Simon.

On 16/12/16 19:31, Donatas Abraitis wrote: Well, it depends,
in our case it's enough 32, never hit this value still.
Sent from my iPhone

On 16 Dec 2016, at 18:43, Simon Kelley

What backlog parameter works well for you?
I'm happy to apply the patch if this is a dial that really
needs to be tweakable, but if there are no downsides to
moving the fixed backlog limit from 5 to 50 or 500, then
let's just do that. There's no point in making people apply
arbitrary configuration options if it can just work.
Cheers,
Simon.

On 07/12/16 13:43, Donatas Abraitis wrote: Of course
patch is tested ;-) Some output: % ./src/dnsmasq --port
1025 --listen-backlog 100 % ss -ntl sport = :1025
Recv-Q Send-Q Local Address:Port Peer Address:Port 0
100 :::1025 :::* 0 100 *:1025
On Wed, Dec 7, 2016 at 3:28 PM, Albert ARIBAUD

Post by Albert ARIBAUD
Hi Donatas,
Le Wed, 7 Dec 2016 14:43:22 +0200 Donatas Abraitis

Post by Donatas Abraitis
Hi folks,
for our case at Hostinger, we have a problem while
nstat -az | grep TcpExtListenOverflows
ss -ntl sport = :53 State Recv-Q Send-Q Local
Address:Port Peer Address:Port LISTEN 0 5 *:53 *:*
LISTEN 0 5 :::53 :::*
probe kernel.function("tcp_check_req") { tcphdr =
__get_skb_tcphdr($skb); dport =
__tcp_skb_dport(tcphdr) if ($sk->sk_ack_backlog >
$sk->sk_max_ack_backlog) printf("listen queue for
port(%d): %d/%d\n", dport, $sk->sk_ack_backlog,
$sk->sk_max_ack_backlog); }
13/5 listen queue for port(53): 14/5
commit fa610cd424b905720832afc8636373bb132f49c1
Author: Donatas Abraitis
09:58:51 2012 +0200
Add `listen-backlog` option to override default 5
(too small)
diff --git a/src/dnsmasq.h b/src/dnsmasq.h index
4b55bb5..b717df3 100644 --- a/src/dnsmasq.h +++
daemon { struct dhcp_netid_list *force_broadcast,
*bootp_dynamic; struct hostsfile *dhcp_hosts_file,
*dhcp_opts_file, *dynamic_dirs; int dhcp_max,
tftp_max, tftp_mtu; + int listen_backlog; int
dhcp_server_port, dhcp_client_port; int
start_tftp_port, end_tftp_port; unsigned int
min_leasetime; diff --git a/src/network.c
b/src/network.c index d87d08f..1e9d188 100644 ---
*addr, int type, int dienow)
if (type == SOCK_STREAM) { - if (listen(fd, 5)
== -1) + if (listen(fd, daemon->listen_backlog) ==
-1) goto err; } else if (family == AF_INET) diff
--git a/src/option.c b/src/option.c index
d0d9509..220303e 100644 --- a/src/option.c +++
{ #define LOPT_SCRIPT_ARP 347 #define LOPT_DHCPTTL
348 #define LOPT_TFTP_MTU 349 +#define LOPT_BACKLOG
350
#ifdef HAVE_GETOPT_LONG static const struct option
myoption opts[] = { "domain-suffix", 1, 0, 's' }, {
"interface", 1, 0, 'i' }, { "listen-address", 1, 0,
'a' }, + { "listen-backlog", 1, 0, LOPT_BACKLOG
}, { "local-service", 0, 0, LOPT_LOCAL_SERVICE },
{ "bogus-priv", 0, 0, 'b' }, { "bogus-nxdomain", 1,
't', ARG_ONE, "<host_name>", gettext_noop("Specify
default target in an MX record."), NULL }, { 'T',
ARG_ONE, "<integer>", gettext_noop("Specify
time-to-live in seconds for replies from
/etc/hosts."), NULL }, { LOPT_NEGTTL, ARG_ONE,
"<integer>", gettext_noop("Specify time-to-live in
seconds for negative caching."), NULL }, + {
LOPT_BACKLOG, ARG_ONE, "<integer>",
gettext_noop("Set the backlog queue limit."), NULL
}, { LOPT_MAXTTL, ARG_ONE, "<integer>",
gettext_noop("Specify time-to-live in seconds for
maximum TTL to send to clients."), NULL }, {
LOPT_MAXCTTL, ARG_ONE, "<integer>",
gettext_noop("Specify time-to-live ceiling for
cache."), NULL }, { LOPT_MINCTTL, ARG_ONE,
"<integer>", gettext_noop("Specify time-to-live
static int one_opt(int option, char *arg, char
*errstr, char *gen_err, int comma
ret_err(gen_err); /* error */ break; } - + +
case LOPT_BACKLOG: /* --listen-backlog */ + if
(!atoi_check(arg, &daemon->listen_backlog)) +
ret_err(gen_err); + break; case 'a': /*
--listen-address */ case LOPT_AUTHPEER: /*
read_opts(int argc, char **argv, char
*compile_opts) daemon->cachesize = CACHESIZ;
daemon->ftabsize = FTABSIZ; daemon->port =
NAMESERVER_PORT; + daemon->listen_backlog = 5;
daemon->dhcp_client_port = DHCP_CLIENT_PORT;
daemon->dhcp_server_port = DHCP_SERVER_PORT;
daemon->default_resolv.is_default = 1;

I am not qualified to determine if your patch is the
right solution to your problem, but FWIW, I find this
patch clear enough and I assume you have tested it :)
and that it actually solves the issue for you. The
- it would be nice to also add a description for the
option and its rationale to the manpage;
- is there a way for dnsmasq to detect excessive
backlog and emit a diagnostic message pointing the
operator to the existence and use of the
listen-backlog option, and if so, could you add this
to the patch?
Note that I am in no way a maintainer of dnsmasq, so
neither my review nor my questions should be mistaken
for an acceptation of the patch -- only Simon can
accept patches.
Amicalement, -- Albert.

_______________________________________________
Dnsmasq-discuss mailing list
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

_______________________________________________

Post by Donatas Abraitis

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