Re: [PATCH] ip.7: Add not supported by SOCK_STREAM to socket options

[Alejandro Colomar <alx@kernel.org>]

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Hi Oliver,

On Sat, Mar 16, 2024 at 02:41:13PM -0400, Oliver Crumrine wrote:
> On Sat, Mar 16, 2024 at 08:33:36PM +0100, Alejandro Colomar wrote:
> > Hi Oliver,
> > 
> > On Wed, Mar 13, 2024 at 02:27:17PM -0400, Oliver Crumrine wrote:
> > > > 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;
      |             ^~~~~~~~


> #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.

> 	
> 	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?

> }

> #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

>     		        //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;
> }

> #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);
> 
> 
> }

> #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/>

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