On Sun, Mar 17, 2024 at 03:02:53AM +0100, Alejandro Colomar wrote:

Hi Oliver,

On Sat, Mar 16, 2024 at 02:41:13PM -0400, Oliver Crumrine wrote:

quoted

On Sat, Mar 16, 2024 at 08:33:36PM +0100, Alejandro Colomar wrote:

quoted

Hi Oliver,

On Wed, Mar 13, 2024 at 02:27:17PM -0400, Oliver Crumrine wrote:

quoted

quoted

Hi Alex,
I apologize for your repeated troubles with my test program.
I have attached a video of myself using it in the method that I
described to you. (I emailed you off-list as to avoid sending a 12
MB video to the whole list)

If you are using it in the same way that works for me, I don't know
what the problem is. If I could've been clearer in my instructions, let
me know for the future.

Thanks,
Oliver

Hi Alex,
Were you able to make any progress whatsoever with this test program?

I'm sorry, but I haven't been able to reproduce the behavior.  The test
programs have several problems which I reported in previous mails.
Maybe there's something that makes it unstable and in your system
behaves differently?  Please clean up those examples, and try to run
them in a different system, and maybe then I can reproduce it.

Have a lovely day!
Alex


$ uname -a
Linux debian 6.8.0-rc7-alx-dirty #3 SMP PREEMPT_DYNAMIC Mon Mar  4 15:24:33 CET 2024 x86_64 GNU/Linux

-- 
<https://www.alejandro-colomar.es/>

Hi Alex,
I have cleaned up my test programs. I have also tested them on other
systems (including on systems which I had installed the rc7 kernel
onto). In the very slight chance that your netcat isn't working, (very 
narrow chances, but still there), I have attached client programs to go 
along with the servers.
Thanks,
Oliver

I still get warnings when compiling them.  There's clearly dead code in
them.

alx@debian:~/tmp$ cc -Wall -Wextra ds.c -o ds
ds.c: In function ‘main’:
ds.c:26:14: warning: unused variable ‘buf’ [-Wunused-variable]
   26 |         char buf[BUFSIZ];
      |              ^~~
alx@debian:~/tmp$ cc -Wall -Wextra dc.c -o dc
dc.c: In function ‘main’:
dc.c:16:13: warning: unused variable ‘send_len’ [-Wunused-variable]
   16 |         int send_len;
      |             ^~~~~~~~

quoted

#include <stdio.h>
#include <err.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>

#define PORT 8888 //The port on which to send data
#define ADDR "127.0.0.1" //The internet address to send packets to

int main(void){
	int s;
	struct sockaddr_in server_addr;

	int send_len;
	char buf[] = "testing 1 2 3\n";

	s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if(s == -1){
		err(1, "error creating socket");
	}

	memset((char*)&server_addr, 0, sizeof(server_addr));

You shouldn't be casting pointers that you pass to memset(3).  It
accepts almost anything.  That cast defeats the little type safety that
it has.

quoted

	
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(PORT);
	if(inet_pton(AF_INET, ADDR, &server_addr.sin_addr) != 1){ //I realize I'm checking the return value differently here. If you read the man page for inet_pton, it'll make sense.
		err(1, "error converting network address");
	}

	if(sendto(s, buf, strlen(buf), 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1){
		err(1, "error sending data");
	}
	
	close(s);

Why two blanks here?

quoted

}

quoted

#include<stdio.h>
#include<err.h>
#include<string.h>
#include<stdlib.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<unistd.h>

#define PORT 8888	//The port on which to listen for incoming data


//Hi Alex,
//These are the two lines that allow you to switch between the three socket options outlined in my patch
//The socket options tell the kernel to add a control message (cmsg), allowing the program
//to recieve the data it is requesting. The three options are: IP_RECVTOS for the type of service byte,
//IP_RECVORIGDSTADDR for the orignial dst address, and IP_PKTINFO for some random packet info.
#define SOCKOPT IP_RECVORIGDSTADDR
//This field is synonymous with the above one. Valid options are: IP_TOS, IP_ORIGDSTADDR, and IP_PKTINFO
#define RECIVEOPTION IP_ORIGDSTADDR

int main(void){
	struct sockaddr_in local_addr;
	
	int s;
	int recv_len;
	char buf[BUFSIZ];
	
	s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (s == -1){
		err(1, "error creating socket");
	}
	
	memset((char *) &local_addr, 0, sizeof(local_addr));
	
	local_addr.sin_family = AF_INET;
	local_addr.sin_port = htons(PORT);
	local_addr.sin_addr.s_addr = htonl(INADDR_ANY);

	int yes = 1;
	if(setsockopt(s, IPPROTO_IP, SOCKOPT, &yes, sizeof(yes)) == -1){
		err(1, "error setting socket option");
	}


	if(bind(s, (struct sockaddr*)&local_addr, sizeof(local_addr) ) == -1){
		err(1, "error binding to port. try changing it or running as root");
	}

	while(1){
		struct msghdr mhdr;
		struct iovec iov[1];
		struct cmsghdr *cmhdr;
		char control[1000];
		char databuf[1500];
		unsigned char tos = 0;
		
		mhdr.msg_name = &local_addr;
		mhdr.msg_namelen = sizeof(local_addr);
		mhdr.msg_iov = iov;
		mhdr.msg_iovlen = 1;
		mhdr.msg_control = &control;
		mhdr.msg_controllen = sizeof(control);
		iov[0].iov_base = databuf;
		iov[0].iov_len = sizeof(databuf);
		memset(databuf, 0, sizeof(databuf));	
		
		//this is blocking
		if ((recv_len = recvmsg(s, &mhdr, 0)) == -1){
			err(1, "recvmsg");
		}
		cmhdr = CMSG_FIRSTHDR(&mhdr);
		while (cmhdr) {
			printf("cmsg recieved\n");
    		    if (cmhdr->cmsg_level == IPPROTO_IP && cmhdr->cmsg_type == RECIVEOPTION) {

Don't mix spaces and tabs.


Have a lovely night!
Alex

quoted

    		        //read the byte recieved
			    tos = ((unsigned char *)CMSG_DATA(cmhdr))[0];
    		    }
    		    cmhdr = CMSG_NXTHDR(&mhdr, cmhdr);
    		}
		//print out the first byte of data recieved in hex. You can verify this in wireshark if you like.
    		printf("data read: %sbyte = %02X\n", databuf, tos); 	
		
	}

	close(s);
	return 0;
}

quoted

#include <stdio.h>
#include <err.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>

#define PORT 8888 //The port on which to send data
#define ADDR "127.0.0.1" //The internet address to send packets to

int main(void){
	int s;
	struct sockaddr_in server_addr;

	int send_len;
	char buf[] = "testing 1 2 3\n";

	s = socket(AF_INET, SOCK_STREAM, 0);
	if(s == -1){
		err(1, "error creating socket");
	}

	memset((char*)&server_addr, 0, sizeof(server_addr));
	
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(PORT);
	if(inet_pton(AF_INET, ADDR, &server_addr.sin_addr) != 1){ // I realize I'm checking the return value differently here. If you read the man page for inet_pton, it'll make sense.
		err(1, "error converting network address");
	}

	if(connect(s, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1){
		err(1, "error connecting");
	}
	if(send(s, buf, strlen(buf), 0) == -1){
		err(1, "error sending data");
	}
	
	close(s);


}

quoted

#include<stdio.h>
#include<err.h>
#include<string.h>
#include<stdlib.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<unistd.h>

#define PORT 8888	//The port on which to listen for incoming data


//Hi Alex,
//These are the two lines that allow you to switch between the three socket options outlined in my patch
//The socket options tell the kernel to add a control message (cmsg), allowing the program
//to recieve the data it is requesting. The three options are: IP_RECVTOS for the type of service byte,
//IP_RECVORIGDSTADDR for the orignial dst address, and IP_PKTINFO for some random packet info.
#define SOCKOPT IP_RECVORIGDSTADDR
//This field is synonymous with the above one. Valid options are: IP_TOS, IP_ORIGDSTADDR, and IP_PKTINFO
#define RECIVEOPTION IP_ORIGDSTADDR

int main(void){
	struct sockaddr_in local_addr;
	
	int s;
	int recv_len;
	char buf[BUFSIZ];
	
	s = socket(AF_INET, SOCK_STREAM, 0);
	if (s == -1){
		err(1, "error creating socket");
	}
	
	memset((char *) &local_addr, 0, sizeof(local_addr));
	
	local_addr.sin_family = AF_INET;
	local_addr.sin_port = htons(PORT);
	local_addr.sin_addr.s_addr = htonl(INADDR_ANY);

	int yes = 1;
	if(setsockopt(s, IPPROTO_IP, SOCKOPT, &yes, sizeof(yes)) == -1){
		err(1, "error setting socket option");
	}


	if(bind(s, (struct sockaddr*)&local_addr, sizeof(local_addr) ) == -1){
		err(1, "error binding to port. try changing it or running as root");
	}
	
	if(listen(s, 10) == -1){ //10 is the backlog of un-accepted connections. its just an arbitrary number
		err(1, "error listening on port");
	}

	while(1){
		int connfd = accept(s, (struct sockaddr*)NULL, NULL);
		if(connfd == -1){
			err(1, "error accepting connection");
		}
		if(setsockopt(s, IPPROTO_IP, SOCKOPT, &yes, sizeof(yes)) == -1){ //stream sockets should have this set on the connected socket as well. I left it above for uniformity between the two programs.
			err(1, "error setting socket option");
		}
	
		struct msghdr mhdr;
		struct iovec iov[1];
		struct cmsghdr *cmhdr;
		char control[1000];
		char databuf[1500];
		unsigned char tos = 0;
		
		mhdr.msg_name = &local_addr;
		mhdr.msg_namelen = sizeof(local_addr);
		mhdr.msg_iov = iov;
		mhdr.msg_iovlen = 1;
		mhdr.msg_control = &control;
		mhdr.msg_controllen = sizeof(control);
		iov[0].iov_base = databuf;
		iov[0].iov_len = sizeof(databuf);
		memset(databuf, 0, sizeof(databuf));	
		
		//this is blocking
		if ((recv_len = recvmsg(connfd, &mhdr, 0)) == -1){
			err(1, "recvmsg\n");
		}
		cmhdr = CMSG_FIRSTHDR(&mhdr);
		while (cmhdr) {
			printf("cmsg recieved\n");
    		    if (cmhdr->cmsg_level == IPPROTO_IP && cmhdr->cmsg_type == RECIVEOPTION) {
    		        //read the byte recieved
			    tos = ((unsigned char *)CMSG_DATA(cmhdr))[0];
    		    }
    		    cmhdr = CMSG_NXTHDR(&mhdr, cmhdr);
    		}
		//print out the first byte of data recieved in hex. You can verify this in wireshark if you like.
    		printf("data read: %sbyte = %02X\n", databuf, tos); 	
		close(connfd);
	}

	close(s);
	return 0;
}

-- 
<https://www.alejandro-colomar.es/>

I just realized I had cc linked to a homebrew c compler on my system and
that's why Wall and Wextra weren't giving me the same warnings they were
giving you. Oops.

Anyway, I have put cc back to gcc, and I finally see the unused variable
warnings, and I cleaned them up. 

Peter said on the previous reply to this that netcat only worked for him
when it was forced to IPv4, using the -4 option, so that may be the
issue you are facing with the program.