From f0d276c4d5ce3da5c229a42e6f5d55f5b171167c Mon Sep 17 00:00:00 2001
From: Dylan Lloyd <dylan@dylansserver.com>
Date: Wed, 13 Feb 2013 00:49:47 -0500
Subject: [PATCH] refactored listen.c for clarity

---
 listen.c | 58 ++++++++++++++++++++++++++++----------------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/listen.c b/listen.c
index 4c8eef7..fd7ce87 100644
--- a/listen.c
+++ b/listen.c
@@ -12,16 +12,16 @@
 #include <signal.h>
 #include <libnotify/notify.h>
 
-#define PORT "3490"  // the port users will be connecting to
-
-#define BACKLOG 10	 // how many pending connections queue will hold
+#define PORT "3490"
+#define QUEUE_LENGTH 10
 
+// a function to reap future child processes
 void sigchld_handler(int s)
 {
 	while(waitpid(-1, NULL, WNOHANG) > 0);
 }
 
-// get sockaddr, IPv4
+// look for an IPv4 host:port in an address structure
 void *get_in_addr(struct sockaddr *sa)
 {
 	if (sa->sa_family == AF_INET) {
@@ -31,64 +31,61 @@ void *get_in_addr(struct sockaddr *sa)
 
 int main(void)
 {
-	int sockfd, activefd;  // listen on sockfd, new connection on activefd
-	struct addrinfo hints, *servinfo, *p;
-	struct sockaddr_storage their_addr; // connector's address information
+    // new connections on activefd, always listening on sockfd
+	int sockfd, activefd;
+	struct addrinfo hints, *servinfo, *port;
+	struct sockaddr_storage their_addr;
 	socklen_t sin_size;
 	struct sigaction sa;
-	int yes=1;
 	char source[INET6_ADDRSTRLEN];
-//    char CLIENT_IP[15] = "107.21.205.69\0";
+	int yes=1;
 	int rv;
 
-	memset(&hints, 0, sizeof hints); // make sure the struct is empty
-	hints.ai_family = AF_INET; // IPv4
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = AF_INET;
 	hints.ai_socktype = SOCK_STREAM;
-	hints.ai_flags = AI_PASSIVE; // use my IP
+	hints.ai_flags = AI_PASSIVE;
 
+    // look up local address information
 	if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
 		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
 		return 1;
 	}
 
-    // servinfo now points to a linked list of 1 or more struct addrinfos
-
-	// loop through all the results and bind to the first we can
-	for(p = servinfo; p != NULL; p = p->ai_next) {
-		if ((sockfd = socket(p->ai_family, p->ai_socktype,
-				p->ai_protocol)) == -1) {
+	// loop over available interfaces and try to bind to port
+	for (port = servinfo; port != NULL; port = port->ai_next) {
+		if ((sockfd = socket(port->ai_family, port->ai_socktype,
+				port->ai_protocol)) == -1) {
 			perror("irssi-notify: socket");
 			continue;
 		}
-
 		if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
 				sizeof(int)) == -1) {
 			perror("setsockopt");
 			exit(1);
 		}
-
-		if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
+		if (bind(sockfd, port->ai_addr, port->ai_addrlen) == -1) {
 			close(sockfd);
 			perror("irssi-notify: bind");
 			continue;
 		}
-
 		break;
 	}
 
-	if (p == NULL)  {
+	if (port == NULL)  {
 		fprintf(stderr, "irssi-notify: failed to bind\n");
 		return 2;
 	}
 
-	freeaddrinfo(servinfo); // all done with this structure
+	freeaddrinfo(servinfo);
 
-	if (listen(sockfd, BACKLOG) == -1) {
+	if (listen(sockfd, QUEUE_LENGTH) == -1) {
 		perror("listen");
 		exit(1);
 	}
 
-	sa.sa_handler = sigchld_handler; // reap all dead processes
+    // bind sigchld_handler to reap future child processes
+	sa.sa_handler = sigchld_handler;
 	sigemptyset(&sa.sa_mask);
 	sa.sa_flags = SA_RESTART;
 	if (sigaction(SIGCHLD, &sa, NULL) == -1) {
@@ -98,7 +95,7 @@ int main(void)
 
 	printf("irssi-notify: waiting for connections...\n");
 
-	while(1) {  // main accept() loop
+	while (1) {
 		sin_size = sizeof their_addr;
 		activefd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
 		if (activefd == -1) {
@@ -110,14 +107,17 @@ int main(void)
 			get_in_addr((struct sockaddr *)&their_addr),
 			source, sizeof source);
 
+        // whitelist allowed
         if (strcmp(source, "50.16.219.8") != 0 &&
                 strcmp(source, "127.0.0.1") != 0){
             close(activefd);
             continue;
         }                                                                       
 
-		if (!fork()) { // this is the child process
-			close(sockfd); // child doesn't need the listener
+        // start a child process to handle notifications
+		if (!fork()) {
+            // the child process doesn't need the listener
+			close(sockfd);
             char buf[4096];
             if (recv(activefd, buf, 99, 0) == -1) {
                 perror("recv");
-- 
2.30.2