refactored listen.c for clarity

diff --git a/listen.c b/listen.c
index 4c8eef7..fd7ce87 100644 (file)
--- 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");