error statuses cleanup

README

-1. DESCRIPTION
-
-This is a simple proxy daemon that allows you to forward TCP requests hitting a specified port on a local host to a different port on another host. It is written in ANSI C so it takes a very little space and can be used on embedded devices.
-
-2. INSTALLATION
-
-On Linux compile the software using "make". On Windows use "make" from Cygwin (http://cygwin.com).
-
-To build an executable for Tomato firmware (http://www.polarcloud.com/tomato) you need to have the mipsel toolchain installed. Fetch it with git:
-
-git clone git://repo.or.cz/tomato.git tomato
-
-and follow instructions in the "tools/README.TXT" file.
-
-3. USAGE
-
-Command line syntax goes as follows:
-
-proxy -l local_port -h remote_host -p remote_port [-i "input parser"] [-o "output parser"]
-
-Suppose you want to open port 8080 on a public host and forward all TCP packets to port 80 on machine 192.168.1.2 in the local network. In this case you install proxy on a public host and run it the following command:
-
-proxy -l 8080 -h 192.168.1.2 -p 80
-
-Input parser and output parser are commands through which incoming and outgoing packets can be forwarded. For example to use a "tee" command to log all incoming http data to incoming.txt file you can start proxy with the following options:
-
-proxy -l 8080 -h 192.168.1.2 -p 80 -i "tee -a incoming.txt"
-
-The parser command will receive data from socket to its standard input and should send parsed data to the standard output. It should also flush its output at a reasonable rate to not withhold network communication.
+1. DESCRIPTION
+
+This is a simple proxy daemon that allows you to forward TCP requests hitting a specified port on a local host to a different port on another host. It is written in ANSI C so it takes a very little space and can be used on embedded devices.
+
+2. INSTALLATION
+
+On Linux compile the software using "make". On Windows use "make" from Cygwin (http://cygwin.com).
+
+To build an executable for Tomato firmware (http://www.polarcloud.com/tomato) you need to have the mipsel toolchain installed. Fetch it with git:
+
+git clone git://repo.or.cz/tomato.git tomato
+
+and follow instructions in the "tools/README.TXT" file.
+
+3. USAGE
+
+Command line syntax goes as follows:
+
+proxy -l local_port -h remote_host -p remote_port [-i "input parser"] [-o "output parser"]
+
+Suppose you want to open port 8080 on a public host and forward all TCP packets to port 80 on machine 192.168.1.2 in the local network. In this case you install proxy on a public host and run it the following command:
+
+proxy -l 8080 -h 192.168.1.2 -p 80
+
+Input parser and output parser are commands through which incoming and outgoing packets can be forwarded. For example to use a "tee" command to log all incoming http data to incoming.txt file you can start proxy with the following options:
+
+proxy -l 8080 -h 192.168.1.2 -p 80 -i "tee -a incoming.txt"
+
+The parser command will receive data from socket to its standard input and should send parsed data to the standard output. It should also flush its output at a reasonable rate to not withhold network communication.

proxy.c

@@ -42,9 +42,20 @@
 #include <wait.h>
 
 #define BUF_SIZE 1024
+
 #define READ  0
 #define WRITE 1
 
+#define SERVER_SOCKET_ERROR -1
+#define SERVER_SETSOCKOPT_ERROR -2
+#define SERVER_BIND_ERROR -3
+#define SERVER_LISTEN_ERROR -4
+#define CLIENT_SOCKET_ERROR -5
+#define CLIENT_RESOLVE_ERROR -6
+#define CLIENT_CONNECT_ERROR -7
+#define CREATE_PIPE_ERROR -8
+#define BROKEN_PIPE_ERROR -9
+
 typedef enum {TRUE = 1, FALSE = 0} bool;
 
 int create_socket(int port);
@@ -157,11 +168,11 @@ int create_socket(int port) {
     struct sockaddr_in server_addr;
 
     if ((server_sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
-        return -1;
+        return SERVER_SOCKET_ERROR;
     }
 
     if (setsockopt(server_sock, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0) {
-        return -1;
+        return SERVER_SETSOCKOPT_ERROR;
     }
 
     memset(&server_addr, 0, sizeof(server_addr));
@@ -170,11 +181,11 @@ int create_socket(int port) {
     server_addr.sin_addr.s_addr = INADDR_ANY;
 
     if (bind(server_sock, (struct sockaddr*)&server_addr, sizeof(server_addr)) != 0) {
-        return -1;
+        return SERVER_BIND_ERROR;
     }
 
     if (listen(server_sock, 20) < 0) {
-        return -1;
+        return SERVER_LISTEN_ERROR;
     }
 
     return server_sock;
@@ -197,7 +208,7 @@ void server_loop() {
     struct sockaddr_in client_addr;
     int addrlen = sizeof(client_addr);
 
-    while (1) {
+    while (TRUE) {
         client_sock = accept(server_sock, (struct sockaddr*)&client_addr, &addrlen);
         if (fork() == 0) { // handle client connection in a separate process
             close(server_sock);
@@ -262,7 +273,7 @@ void forward_data_ext(int source_sock, int destination_sock, char *cmd[]) {
 
     if (pipe(pipe_in) < 0 || pipe(pipe_out) < 0) { // create command input and output pipes
         perror("Cannot create pipe");
-        exit(EXIT_FAILURE);
+        exit(CREATE_PIPE_ERROR);
     }
 
     if (fork() == 0) {
@@ -279,7 +290,7 @@ void forward_data_ext(int source_sock, int destination_sock, char *cmd[]) {
         while ((n = recv(source_sock, buffer, BUF_SIZE, 0)) > 0) { // read data from input socket
             if (write(pipe_in[WRITE], buffer, n) < 0) { // write data to input pipe of external command
                 perror("Cannot write to pipe");
-                exit(EXIT_FAILURE);
+                exit(BROKEN_PIPE_ERROR);
             }
             if ((i = read(pipe_out[READ], buffer, BUF_SIZE)) > 0) { // read command output
                 send(destination_sock, buffer, i, 0); // send data to output socket
@@ -301,12 +312,12 @@ int create_connection() {
     int sock;
 
     if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
-        return -2;
+        return CLIENT_SOCKET_ERROR;
     }
 
     if ((server = gethostbyname(remote_host)) == NULL) {
         errno = EFAULT;
-        return -3;
+        return CLIENT_RESOLVE_ERROR;
     }
 
     memset(&server_addr, 0, sizeof(server_addr));
@@ -315,7 +326,7 @@ int create_connection() {
     server_addr.sin_port = htons(remote_port);
 
     if (connect(sock, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
-        return -4;
+        return CLIENT_CONNECT_ERROR;
     }
 
     return sock;