off-by-one

less complicated when the size is known at compile time

luad.c

@@ -8,6 +8,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <errno.h>
 #include <error.h>
 #include <sys/un.h>
@@ -32,7 +33,7 @@ static void handle_sigchld(int num) {
 int open_socket(char * pathname) {
     struct sockaddr_un addr;
     addr.sun_family = AF_UNIX;
-    if(strlen(pathname) > sizeof(addr.sun_path)) {
+    if(strlen(pathname) >= sizeof(addr.sun_path)) {
         die("pathname \"%s\" is too long to  bind as unix socket (max %lu)",
             pathname, sizeof(addr.sun_path));
     }
@@ -115,41 +116,46 @@ struct peer_entry {
     pid_t pid;
     int addrlen;
     struct sockaddr_un addr;
-};
+} peer_entries[500];
 
-int register_peer(struct peer_entry *table, pid_t pid, struct sockaddr_un *addr, int addrlen) {
+
+bool register_peer(pid_t pid, struct sockaddr_un *addr, int addrlen) {
     if(addrlen > sizeof (struct sockaddr_un))
-        return -1;
+        return false;
 
-    struct peer_entry *p = table;
-    while(p->pid != 0 && p->pid != -1)
-        p++;
-    if(p->pid == -1)
-        return -1;
-    p->pid = pid;
-    p->addrlen = addrlen;
-    memcpy(&(p->addr), addr, addrlen);
+    struct peer_entry *p = peer_entries;
+    int peer_entries_max = sizeof peer_entries / sizeof(peer_entries[0]);
+
+    for(int i=0; i < peer_entries_max; i++) {
+        struct peer_entry *p = &peer_entries[i];
+        if(p->pid == 0) {
+            p->pid = pid;
+            p->addrlen = addrlen;
+            memcpy(&(p->addr), addr, addrlen);
+            return true;
+        }
+    }
+    return false;
 }
 
-struct peer_entry* find_peer(struct peer_entry *table, pid_t pid) {
-    while(table->pid != -1) {
-        if(table->pid == pid)
-            return table;
-        table++;
+struct peer_entry* find_peer(pid_t pid) {
+    int peer_entries_max = sizeof peer_entries / sizeof(peer_entries[0]);
+
+    for(int i=0; i < peer_entries_max; i++) {
+        struct peer_entry *p = &peer_entries[i];
+        if(p->pid == pid) {
+            return p;
+        }
     }
     return NULL;
 }
 
-
-
 int main(int argc, char **argv)
 {
     int status;
     lua_State *L = luaL_newstate();
     luaL_openlibs(L);
     int sigpipe_fds[2];
-    struct peer_entry * peer_table = calloc(501, sizeof (struct peer_entry));
-    peer_table[500].pid = -1;
 
     char * socket_path = getenv("LUAD_SOCKET_PATH");
     if(! socket_path) {
@@ -206,14 +212,16 @@ int main(int argc, char **argv)
             continue;
 
         if(pollfds[0].revents) {
-            int len = recvmsg(socket, &msg , 0);
-            int *peer_fds = fds_from_msg(&msg, 5);
-            char *argline = malloc(len);
-            memmove(argline, buf, len);
+            if(find_peer(0)) {
+                int len = recvmsg(socket, &msg , 0);
+                int *peer_fds = fds_from_msg(&msg, 5);
+                char *argline = malloc(len);
+                memmove(argline, buf, len);
 
-            pid_t child_pid = fork_lua(L, argline, len, peer_fds, 5);
-            if(child_pid >= 0) {
-                register_peer(peer_table, child_pid, &peer_addr, msg.msg_namelen);
+                pid_t child_pid = fork_lua(L, argline, len, peer_fds, 5);
+                if(child_pid >= 0) {
+                    register_peer(child_pid, &peer_addr, msg.msg_namelen);
+                }
             }
         }
 
@@ -223,7 +231,7 @@ int main(int argc, char **argv)
 
             read(pollfds[1].fd, buf, sizeof buf);
             while((pid=waitpid(0, &wstatus, WNOHANG)) > 0) {
-                struct peer_entry *peer = find_peer(peer_table, pid);
+                struct peer_entry *peer = find_peer(pid);
                 if(peer) {
                     uint32_t ret = 0;
                     if(WIFEXITED(wstatus)) {