Creation of sockets from scratch using TCP_REPAIR? - c

Question

I'm using TCP_REPAIR to create a pair of already-connected sockets that talk to each other without actually going through the TCP connect flow.
I've tried to use the ideas in LWN for connection repair and their soccr library, but unfortunately, no matter what I do, I always get an ECONNRESET error the moment I try to write data to any of the sockets.
Here's an example of what I've tried:
#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/socket.h>
#include <netinet/tcp.h>
#include <string.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdlib.h>
#include <errno.h>
struct tcp {
char *addr;
uint32_t port;
};
int createSocket(struct tcp src, struct tcp dst) {
int sk, yes = 1;
struct sockaddr_in addr;
sk = socket(AF_INET, SOCK_STREAM, 0);
if (sk < 0) {
printf("Cannot create socket\n");
return -1;
}
if (setsockopt(sk, SOL_TCP, TCP_REPAIR, &yes, sizeof(yes))) {
printf("Cannot set TCP_REPAIR\n");
return -1;
}
if (setsockopt(sk, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) == -1) {
printf("Cannot set SO_REUSEADDR\n");
return -1;
}
memset(&addr,0,sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(src.port);
if (inet_pton(AF_INET, src.addr, &(addr.sin_addr)) < 0) {
printf("Error converting source host:port to binary\n");
return -1;
}
if (bind(sk, (struct sockaddr *) &addr, sizeof(addr))) {
printf("Cannot bind to source port\n");
return -1;
}
memset(&addr,0,sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(dst.port);
if (inet_pton(AF_INET, dst.addr, &(addr.sin_addr)) < 0) {
printf("Error converting destination host:port to binary\n");
return -1;
}
if (connect(sk, (struct sockaddr *) &addr, sizeof(addr))) {
printf("Cannot bind to remote port\n");
return -1;
}
int no = 0;
if (setsockopt(sk, SOL_TCP, TCP_REPAIR, &no, sizeof(no))) {
printf("Cannot set TCP_REPAIR\n");
return -1;
}
return sk;
}
int main(int argc, char **argv) {
struct tcp tcp[2] = {
{"127.0.0.1", 17000},
{"127.0.0.1", 34000}
};
int source_socket = createSocket(tcp[0], tcp[1]);
printf("Source socket created: %d \n",source_socket);
int dest_socket = createSocket(tcp[1], tcp[0]);
printf("Destination socket created: %d \n",dest_socket);
if (source_socket < 0 || dest_socket < 0)
return -1;
char* message = "Hello world";
ssize_t written = write(dest_socket, message, strlen(message)); // ECONNRESET error
if (written < 0) {
printf("Error writing to socket %d\n",errno);
return -1;
}
printf("%ld bytes written\n",written);
char buffer[1024];
ssize_t bytesRead = read(dest_socket, buffer, sizeof(buffer)-1);
printf("Bytes read %ld\n",bytesRead);
buffer[bytesRead] = 0;
printf("Message read: %s\n",buffer);
printf("Finished %d %d \n",source_socket,dest_socket);
return 0;
}
And the output is
Source socket created: 3
Destination socket created: 4
Error writing to socket 104
I get the same result (Connection reset by peer error) if I use the soccr library:
#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/socket.h>
#include <netinet/tcp.h>
#include <string.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdlib.h>
#include <errno.h>
#include "./soccr.h"
struct tcp {
char *addr;
uint32_t port;
uint32_t seq;
uint16_t mss_clamp;
uint16_t wscale;
};
int createSocket(struct tcp src, struct tcp dst) {
int sk, yes = 1;
union libsoccr_addr src_addr, dst_addr;
struct libsoccr_sk_data data = {};
struct libsoccr_sk *so;
data.state = TCP_ESTABLISHED;
data.inq_seq = dst.seq;
data.outq_seq = src.seq;
sk = socket(AF_INET, SOCK_STREAM, 0);
if (sk < 0) {
printf("Cannot create socket. Errno %d\n",errno);
return -1;
}
so = libsoccr_pause(sk);
if (setsockopt(sk, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) == -1) {
printf("Cannot set socket options. Errno %d\n",errno);
return -1;
}
src_addr.v4.sin_family = AF_INET;
src_addr.v4.sin_port = htons(src.port);
if (inet_pton(AF_INET, src.addr, &src_addr.v4.sin_addr) != 1) {
printf("Cannot convert source host:port to binary. Errno %d\n",errno);
return -1;
}
dst_addr.v4.sin_family = AF_INET;
dst_addr.v4.sin_port = htons(dst.port);
if (inet_pton(AF_INET, dst.addr, &(dst_addr.v4.sin_addr)) != 1) {
printf("Cannot convert destination host:port to binary. Errno %d\n",errno);
return -1;
}
libsoccr_set_addr(so, 1, &src_addr, 0);
libsoccr_set_addr(so, 0, &dst_addr, 0);
data.snd_wscale = src.wscale;
data.rcv_wscale = dst.wscale;
data.mss_clamp = src.mss_clamp;
data.opt_mask = TCPI_OPT_WSCALE | TCPOPT_MAXSEG;
if (libsoccr_restore(so, &data, sizeof(data)) < 0) {
printf("Cannot apply restore options. Errno %d\n",errno);
return -1;
}
libsoccr_resume(so);
return sk;
}
int main(int argc, char **argv) {
struct tcp tcp[2] = {
{"127.0.0.1", 17000, 5000000, 1460, 7},
{"127.0.0.1", 34000, 6000000, 1460, 7}
};
int source_socket = createSocket(tcp[0], tcp[1]);
printf("Source socket created: %d \n",source_socket);
int dest_socket = createSocket(tcp[1], tcp[0]);
printf("Destination socket created: %d \n",dest_socket);
if (source_socket < 0 || dest_socket < 0)
return -1;
char* message = "Hello world";
ssize_t written = write(source_socket, message, strlen(message));
if (written < 0) {
printf("Error writing to socket %d\n",errno);
return -1;
}
printf("%ld bytes written\n",written);
char buffer[1024];
ssize_t bytesRead = read(dest_socket, buffer, sizeof(buffer)-1);
printf("Bytes read %ld\n",bytesRead);
buffer[bytesRead] = 0;
printf("Message read: %s\n",buffer);
printf("Finished\n");
return 0;
}
Any ideas about what I might be doing wrong here?