feat: first commit

imap.c

@@ -0,0 +1,239 @@
+/*-
+ * Copyright (c) 2024, Lorenzo Torres
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the <organization> nor the
+ *    names of its contributors may be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/select.h>
+#include <syslog.h>
+#include <errno.h>
+#include <config.h>
+#include <imap.h>
+
+uint8_t imap_init(uint8_t daemon, imap_t *instance)
+{
+    imap_t imap;
+
+    /* Create a new socket using IPv4 protocol */
+    if ((imap.socket = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
+        perror("socker");
+        return 1;
+    }
+
+    bzero(&imap.addr, sizeof(struct sockaddr_in));
+
+    imap.addr.sin_family = AF_INET;
+    /* From config.h */
+    imap.addr.sin_port = htons(IMAP_PORT);
+    
+    if (INADDR_ANY) {
+        imap.addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    }
+
+    /* Bind the socket to the specified address */
+    if ((bind(imap.socket, (struct sockaddr *)&imap.addr, sizeof(imap.addr)) < 0)) {
+        perror("bind");
+        return 2;
+    }
+
+    /* If daemon mode is activated, detach */
+    if (daemon) {
+        switch (fork()) {
+            case -1:
+                perror("fork");
+                return 3;
+                break;
+            default:
+                close(imap.socket);
+                free(instance);
+                exit(0);
+                break;
+            case 0:
+                break;
+        }
+    }
+
+    memcpy(instance, &imap, sizeof(imap));
+
+    return 0;
+}
+
+int imap_get_max_fd(client_list *list, int master)
+{
+    int max_fd = 0;
+    client_list *node = list;
+
+    while (node != NULL) {
+        if (max_fd < node->socket) {
+            max_fd = node->socket;
+        }
+
+        node = node->next;
+    }
+
+    return max_fd > master ? max_fd : master;
+}
+
+client_list *imap_add_client(client_list *list, int sock)
+{
+    client_list *node = (client_list *) malloc(sizeof(client_list));
+    node->socket = sock;
+    node->next = list;
+    node->prev = NULL;
+    if (list != NULL) {
+        list->prev = node;
+    }
+
+    return node; 
+}
+
+client_list *imap_remove_client(client_list *list, client_list *node)
+{
+    if (node->next != NULL) {
+        node->next->prev = node->prev;
+    }
+
+    if (node->prev != NULL) {
+        node->prev->next = node->next;
+    }
+
+    close(node->socket);
+
+    if (node == list) {
+        return NULL;
+    }
+
+    return list;
+}
+
+client_list *imap_remove_sock(client_list *list, int sock)
+{
+    client_list *node = list;
+
+    while (node != NULL && node->socket != sock) {
+        node = node->next;
+    }
+
+    if (node != NULL) {
+        imap_remove_client(list, node);
+    }
+
+    return node;
+}
+
+void imap_start(imap_t *instance)
+{
+    int activity, max_fd, connection;
+    size_t bytes_read;
+    char buf[CMD_MAX_SIZE];
+    /* List of all the file descriptors (sockets) being used. */
+    fd_set fds;
+    instance->clients = NULL;
+    client_list *node = instance->clients;
+    client_list *tmp = instance->clients;
+
+    listen(instance->socket, BACKLOG);
+    syslog(LOG_INFO, "Listening on %d.", IMAP_PORT);
+
+    for (;;) {
+        FD_ZERO(&fds);
+        FD_SET(instance->socket, &fds);
+        node = instance->clients;
+
+        while (node != NULL) {
+            FD_SET(node->socket, &fds);
+            node = node->next;
+        }
+
+        max_fd = imap_get_max_fd(instance->clients, instance->socket);
+        activity = select(max_fd + 1, &fds, NULL, NULL, NULL);
+
+        if ((activity < 0) && (errno!=EINTR)) {
+            perror("select");
+        }
+
+        /* New connection. */
+        if (FD_ISSET(instance->socket, &fds)) {
+            if ((connection = accept(instance->socket, NULL, NULL)) < 0) {
+                perror("accept");
+                syslog(LOG_ERR, "Connection failed.");
+                imap_close(instance);
+                exit(EXIT_FAILURE);
+            }
+
+            instance->clients = imap_add_client(instance->clients, connection);
+            syslog(LOG_INFO, "Connection enstablished.");
+            FD_SET(connection, &fds);
+        }
+
+        node = instance->clients;
+        tmp = node;
+        while (node != NULL) {
+            connection = node->socket;
+            tmp = node->next;
+            
+            if (FD_ISSET(connection, &fds)) {
+                /* Error occured. */
+                if ((bytes_read = read(connection, buf, CMD_MAX_SIZE)) < 0) {
+                    perror("recv");
+                    instance->clients = imap_remove_client(instance->clients, node);
+                    free(node);
+                    FD_CLR(connection, &fds);
+                    syslog(LOG_ERR, "Failed to receive data.");
+                /* Somebody disconnected */
+                }  else if (bytes_read == 0) {
+                    instance->clients = imap_remove_client(instance->clients, node);
+                    free(node);
+                    FD_CLR(connection, &fds);
+                    syslog(LOG_INFO, "Connection closed.");
+                } else {
+                    buf[bytes_read] = '\0';
+                }
+            }
+
+            node = tmp;
+        }
+    }
+}
+
+void imap_close(imap_t *instance)
+{
+    client_list *node = instance->clients;
+    client_list *tmp = node;
+    while (node != NULL) {
+        close(node->socket);
+        tmp = node->next;
+        free(node);
+        node = tmp;
+    }
+
+    close(instance->socket);
+    free(instance);
+}