Hello guys,
Today, I found a weird problem when I was learning to enable SO_KEEPALIVE for a specific socket. I use setsockopt to enable keepalive firstly, and then use getsockopt to show if it is enabled correctly.

My code snippet is listed below:

Dlang version:

import core.sys.posix.sys.socket;
import core.sys.posix.netinet.in_;
import std.c.stdio;

void main() {
	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	int flag = 1;
	size_t size;
	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t)flag.sizeof);
	flag = 0;
	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t*)&size);
	printf("%d\n", flag);
}

C version:

#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>

int main() {
	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	int flag = 1;
	size_t size;
	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t)sizeof(flag));
	flag = 0;
	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t*)&size);
	printf("%d\n", flag);
	return 0;
}

Dlang version always prints 0, which means keepalive is not enabled, while C version can almost display 1  all the time as expected.

So is there anything wrong inside the code? If not, whose behavior is correct?

On Sunday, 24 May 2015 at 16:51:44 UTC, CodeSun wrote:
> Hello guys,
> Today, I found a weird problem when I was learning to enable SO_KEEPALIVE for a specific socket. I use setsockopt to enable keepalive firstly, and then use getsockopt to show if it is enabled correctly.
>
> My code snippet is listed below:
>
> Dlang version:
>
> import core.sys.posix.sys.socket;
> import core.sys.posix.netinet.in_;
> import std.c.stdio;
>
> void main() {
> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
> 	int flag = 1;
> 	size_t size;
> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t)flag.sizeof);
> 	flag = 0;
> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t*)&size);
> 	printf("%d\n", flag);
> }
>
> C version:
>
> #include <sys/socket.h>
> #include <arpa/inet.h>
> #include <stdio.h>
>
> int main() {
> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
> 	int flag = 1;
> 	size_t size;
> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t)sizeof(flag));
> 	flag = 0;
> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t*)&size);
> 	printf("%d\n", flag);
> 	return 0;
> }
>
> Dlang version always prints 0, which means keepalive is not enabled, while C version can almost display 1  all the time as expected.
>
> So is there anything wrong inside the code? If not, whose behavior is correct?

Could you check the return value of "setsockopt"? Make sure it returns 0 as an indicator of successful operation. If so, then we can think about it further.

On Sunday, 24 May 2015 at 16:51:44 UTC, CodeSun wrote:
> Hello guys,
> Today, I found a weird problem when I was learning to enable SO_KEEPALIVE for a specific socket. I use setsockopt to enable keepalive firstly, and then use getsockopt to show if it is enabled correctly.
>
> My code snippet is listed below:
>
> Dlang version:
>
> import core.sys.posix.sys.socket;
> import core.sys.posix.netinet.in_;
> import std.c.stdio;
>
> void main() {
> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
> 	int flag = 1;
> 	size_t size;
> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t)flag.sizeof);
> 	flag = 0;
> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t*)&size);
> 	printf("%d\n", flag);
> }
>
> C version:
>
> #include <sys/socket.h>
> #include <arpa/inet.h>
> #include <stdio.h>
>
> int main() {
> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
> 	int flag = 1;
> 	size_t size;
> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t)sizeof(flag));
> 	flag = 0;
> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t*)&size);
> 	printf("%d\n", flag);
> 	return 0;
> }
>
> Dlang version always prints 0, which means keepalive is not enabled, while C version can almost display 1  all the time as expected.
>
> So is there anything wrong inside the code? If not, whose behavior is correct?

Cause your code is wrong:
"If the size of the option value is greater than option_len, the value stored in the object pointed to by the option_value
       argument shall be silently truncated. Otherwise, the object pointed to by the option_len argument shall be modified to indicate the  actual
       length of the value."

So because you have size set to 0 it will not work, you mast call it again and than it will probably work.

In C this work because size is not initialize which mean it could be anything

On Sunday, 24 May 2015 at 21:11:34 UTC, Daniel Kozak wrote:
> On Sunday, 24 May 2015 at 16:51:44 UTC, CodeSun wrote:
>> Hello guys,
>> Today, I found a weird problem when I was learning to enable SO_KEEPALIVE for a specific socket. I use setsockopt to enable keepalive firstly, and then use getsockopt to show if it is enabled correctly.
>>
>> My code snippet is listed below:
>>
>> Dlang version:
>>
>> import core.sys.posix.sys.socket;
>> import core.sys.posix.netinet.in_;
>> import std.c.stdio;
>>
>> void main() {
>> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
>> 	int flag = 1;
>> 	size_t size;
>> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t)flag.sizeof);
>> 	flag = 0;
>> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t*)&size);
>> 	printf("%d\n", flag);
>> }
>>
>> C version:
>>
>> #include <sys/socket.h>
>> #include <arpa/inet.h>
>> #include <stdio.h>
>>
>> int main() {
>> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
>> 	int flag = 1;
>> 	size_t size;
>> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t)sizeof(flag));
>> 	flag = 0;
>> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t*)&size);
>> 	printf("%d\n", flag);
>> 	return 0;
>> }
>>
>> Dlang version always prints 0, which means keepalive is not enabled, while C version can almost display 1  all the time as expected.
>>
>> So is there anything wrong inside the code? If not, whose behavior is correct?
>
> Cause your code is wrong:
> "If the size of the option value is greater than option_len, the value stored in the object pointed to by the option_value
>        argument shall be silently truncated. Otherwise, the object pointed to by the option_len argument shall be modified to indicate the  actual
>        length of the value."
>
> So because you have size set to 0 it will not work, you mast call it again and than it will probably work.
>
> In C this work because size is not initialize which mean it could be anything
*call it again with right size and than it will probably work

On Sunday, 24 May 2015 at 21:13:02 UTC, Daniel Kozak wrote:
> On Sunday, 24 May 2015 at 21:11:34 UTC, Daniel Kozak wrote:
>> On Sunday, 24 May 2015 at 16:51:44 UTC, CodeSun wrote:
>>> Hello guys,
>>> Today, I found a weird problem when I was learning to enable SO_KEEPALIVE for a specific socket. I use setsockopt to enable keepalive firstly, and then use getsockopt to show if it is enabled correctly.
>>>
>>> My code snippet is listed below:
>>>
>>> Dlang version:
>>>
>>> import core.sys.posix.sys.socket;
>>> import core.sys.posix.netinet.in_;
>>> import std.c.stdio;
>>>
>>> void main() {
>>> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
>>> 	int flag = 1;
>>> 	size_t size;
>>> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t)flag.sizeof);
>>> 	flag = 0;
>>> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t*)&size);
>>> 	printf("%d\n", flag);
>>> }
>>>
>>> C version:
>>>
>>> #include <sys/socket.h>
>>> #include <arpa/inet.h>
>>> #include <stdio.h>
>>>
>>> int main() {
>>> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
>>> 	int flag = 1;
>>> 	size_t size;
>>> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t)sizeof(flag));
>>> 	flag = 0;
>>> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t*)&size);
>>> 	printf("%d\n", flag);
>>> 	return 0;
>>> }
>>>
>>> Dlang version always prints 0, which means keepalive is not enabled, while C version can almost display 1  all the time as expected.
>>>
>>> So is there anything wrong inside the code? If not, whose behavior is correct?
>>
>> Cause your code is wrong:
>> "If the size of the option value is greater than option_len, the value stored in the object pointed to by the option_value
>>       argument shall be silently truncated. Otherwise, the object pointed to by the option_len argument shall be modified to indicate the  actual
>>       length of the value."
>>
>> So because you have size set to 0 it will not work, you mast call it again and than it will probably work.
>>
>> In C this work because size is not initialize which mean it could be anything
> *call it again with right size and than it will probably work

I mean call it with something big enought, size than should be modified to real size

On Sunday, 24 May 2015 at 21:11:34 UTC, Daniel Kozak wrote:
> On Sunday, 24 May 2015 at 16:51:44 UTC, CodeSun wrote:
>> Hello guys,
>> Today, I found a weird problem when I was learning to enable SO_KEEPALIVE for a specific socket. I use setsockopt to enable keepalive firstly, and then use getsockopt to show if it is enabled correctly.
>>
>> My code snippet is listed below:
>>
>> Dlang version:
>>
>> import core.sys.posix.sys.socket;
>> import core.sys.posix.netinet.in_;
>> import std.c.stdio;
>>
>> void main() {
>> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
>> 	int flag = 1;
>> 	size_t size;
>> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t)flag.sizeof);
>> 	flag = 0;
>> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, cast(socklen_t*)&size);
>> 	printf("%d\n", flag);
>> }
>>
>> C version:
>>
>> #include <sys/socket.h>
>> #include <arpa/inet.h>
>> #include <stdio.h>
>>
>> int main() {
>> 	int sfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
>> 	int flag = 1;
>> 	size_t size;
>> 	setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t)sizeof(flag));
>> 	flag = 0;
>> 	getsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, &flag, (socklen_t*)&size);
>> 	printf("%d\n", flag);
>> 	return 0;
>> }
>>
>> Dlang version always prints 0, which means keepalive is not enabled, while C version can almost display 1  all the time as expected.
>>
>> So is there anything wrong inside the code? If not, whose behavior is correct?
>
> Cause your code is wrong:
> "If the size of the option value is greater than option_len, the value stored in the object pointed to by the option_value
>        argument shall be silently truncated. Otherwise, the object pointed to by the option_len argument shall be modified to indicate the  actual
>        length of the value."
>
> So because you have size set to 0 it will not work, you mast call it again and than it will probably work.
>
> In C this work because size is not initialize which mean it could be anything

You are right, thx.