Hi Oliver,
On Sun, Mar 17, 2024 at 05:02:39AM -0400, Oliver Crumrine wrote:
> 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.
Okay, with the programs below, and after some whitespace fixes, I see
the following diff of the servers, which sounds reasonable:
$ diff -u d.c s.c
--- d.c 2024-03-17 14:27:26.476377947 +0100
+++ s.c 2024-03-17 14:27:36.800391759 +0100
@@ -24,7 +24,7 @@
struct sockaddr_in local_addr;
int s;
- s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+ s = socket(AF_INET, SOCK_STREAM, 0);
if (s == -1)
err(1, "error creating socket");
@@ -40,8 +40,17 @@
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 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;
@@ -60,9 +69,9 @@
memset(databuf, 0, sizeof(databuf));
//this is blocking
- int msglen = recvmsg(s, &mhdr, 0);
+ int msglen = recvmsg(connfd, &mhdr, 0);
if (msglen == -1)
- err(1, "recvmsg");
+ err(1, "recvmsg\n");
cmhdr = CMSG_FIRSTHDR(&mhdr);
while (cmhdr) {
@@ -75,6 +84,7 @@
}
//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);
> 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.
And the programs behave as reported when adding -4.
> #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;
>
> char buf[] = "testing 1 2 3\n";
>
> s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
Why use IPPROTO_UDP? ip(7)'s SYNOPSIS uses 0. Are there any other
protocols available with (AF_INET, SOCK_DGRAM)?
Now about the patch, it seems to miss IP_RETOPTS, which is also handled
in ip_cmsg_recv_offset()? Or am I missing something?
Please resend the programs when you send v2 of the patch, not send the
client programs, and show a diff of both programs.
Have a lovely day!
Alex
> if(s == -1){
> err(1, "error creating socket");
> }
>
> memset(&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(sendto(s, buf, strlen(buf), 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -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;
>
> s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
> if (s == -1){
> err(1, "error creating socket");
> }
>
> memset(&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[BUFSIZ];
> 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
> int msglen = recvmsg(s, &mhdr, 0);
> if (msglen == -1){
> err(1, "recvmsg");
> }
> 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(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;
>
> char buf[] = "testing 1 2 3\n";
>
> s = socket(AF_INET, SOCK_STREAM, 0);
> if(s == -1){
> err(1, "error creating socket");
> }
>
> memset(&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;
>
> s = socket(AF_INET, SOCK_STREAM, 0);
> if (s == -1){
> err(1, "error creating socket");
> }
>
> memset(&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[BUFSIZ];
> 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
> int msglen = recvmsg(connfd, &mhdr, 0);
> if (msglen == -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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