Fix overwriting of the second argument (address) to connect(2) withou…

…t restoring it, close #70

The code in connect_pre_handle() was overwriting the address parameter passed to the connect(2) system call, but it was not restoring the original value before the call returned. This could lead to issues if the caller of connect(2) was relying on the original address value.

To fix this, the code now saves the original address value in the socket_info struct, and then restores it in the connect_exiting_handle() function before the system call returns.

graftcp.c

@@ -245,10 +245,15 @@ void connect_pre_handle(struct proc_info *pinfp)
 		return;
 	}
 
-	if (dest_sa.sin_family == AF_INET) /* IPv4 */
+	if (dest_sa.sin_family == AF_INET) { /* IPv4 */
+		memcpy(si->dest_addr, &dest_sa, sizeof(dest_sa));
+		si->dest_addr_len = sizeof(dest_sa);
 		putdata(pinfp->pid, addr, (char *)&PROXY_SA, sizeof(PROXY_SA));
-	else /* IPv6 */
+	} else { /* IPv6 */
+		memcpy(si->dest_addr, &dest_sa6, sizeof(dest_sa6));
+		si->dest_addr_len = sizeof(dest_sa6);
 		putdata(pinfp->pid, addr, (char *)&PROXY_SA6, sizeof(PROXY_SA6));
+	}
 
 	char buf[1024] = { 0 };
 	strcpy(buf, dest_ip_addr_str);
@@ -306,6 +311,16 @@ void socket_exiting_handle(struct proc_info *pinfp, int fd)
 	add_socket_info(si);
 }
 
+void connect_exiting_handle(struct proc_info *pinfp)
+{
+	int socket_fd = get_syscall_arg(pinfp->pid, 0);
+	struct socket_info *si = find_socket_info((socket_fd << 31) + pinfp->pid);
+	if (si == NULL || si->dest_addr_len == 0)
+		return;
+	long addr = get_syscall_arg(pinfp->pid, 1);
+	putdata(pinfp->pid, addr, si->dest_addr, si->dest_addr_len);
+}
+
 void do_child(struct graftcp_conf *conf, int argc, char **argv)
 {
 	char *args[argc + 1];
@@ -409,6 +424,9 @@ int trace_syscall_exiting(struct proc_info *pinfp)
 		}
 		socket_exiting_handle(pinfp, child_ret);
 		break;
+	case SYS_connect:
+		connect_exiting_handle(pinfp);
+		break;
 	}
 end:
 	pinfp->flags &= ~FLAG_INSYSCALL;

graftcp.h

@@ -87,6 +87,8 @@ struct socket_info {
 	uint64_t magic_fd;
 	int domain;
 	int type;
+	size_t dest_addr_len;
+	char dest_addr[sizeof(struct sockaddr_in6)];
 	struct timeval conn_ti;
 	UT_hash_handle hh;	/* makes this structure hashable */
 };