receiving UDP with sock_recvmsg() in kernel results in "14

Poison Nuke · 06-22-2018, 07:58 AM

Hello,

has someone an idea, why I get constantly an error 14? Sometimes (like every 100 UDP packets), there is no error and I can process the packet.

Regarding to another forum, the buffer might not be correct initialized, but I cant see why:

Code:

int ksocket_receive(struct socket* sock, struct sockaddr_in* addr, unsigned char* buf, int len) {
	struct msghdr msg;
	struct iovec iov;
	mm_segment_t oldfs;
	int size = 0;

	if (sock->sk == NULL) return 0;

	iov.iov_base = buf;
	iov.iov_len = len;


	msg.msg_flags = 0;
	msg.msg_name = addr;
	msg.msg_namelen = sizeof(struct sockaddr_in);
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_iter.iov = &iov;
	msg.msg_iter.count = len;
	msg.msg_iter.type = ITER_IOVEC;
	msg.msg_iter.nr_segs = 1;
	msg.msg_control = NULL;

	oldfs = get_fs();
	set_fs(KERNEL_DS);
	size = sock_recvmsg(sock, &msg, msg.msg_flags);
	set_fs(oldfs);

	return size;
}

int bufsize = 10;
unsigned char buf[bufsize + 1];
memset(&buf, 0, bufsize + 1);
size = ksocket_receive(kthread->sock, &kthread->addr, buf, bufsize);

can anyone point me in the right direction?

rtmistler · 06-22-2018, 02:13 PM

errno value 14 is EFAULT.

Please check the manual page for recvmsg() to learn what it that return value can mean.

Poison Nuke · 06-22-2018, 05:56 PM

Quote:

Originally Posted by rtmistler

errno value 14 is EFAULT.

Please check the manual page for recvmsg() to learn what it that return value can mean.

The answer to that is in the thread-title. Ok Ive only written implicitly that the buffer-pointer address is meant by that.

But as Iam asking, I do not know how that is possible. The buffer is initialized as array and set to zero with memset. I have double checked if any parameter is given as pointer or value and for me in looks like as there is everything fine. And as mentioned, the strange thing is, every 100 packets or so it is working.

So why is the buffer-pointer pointing to nowhere in 99% of the cases? Have I missed any star or ampersand ?

Poison Nuke · 07-27-2018, 03:49 AM

so is this an bug in the kernel? If yes, is there any suitable workaround?

crts · 07-29-2018, 05:59 PM

Nevermind ...