dhcprelay: fix usage text. Simplify and make code more readable.

 Add TODOs.

2 files changed, 75 insertions, 65 deletions

diff --git a/include/usage.h b/include/usage.h
index cbbd7516a..c36a3bbd7 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -802,10 +802,9 @@
        "/dev/sda3             17381728  17107080    274648      98% /\n"
 
 #define dhcprelay_trivial_usage \
-       "[client1,client2,...] [server_device]"
+       "CLIENT_IFACE[,CLIENT_IFACE2...] SERVER_IFACE [SERVER_IP]"
 #define dhcprelay_full_usage "\n\n" \
-       "Relay dhcp requests from client devices to server device.\n" \
-       "Pass clients as CSV"
+       "Relay DHCP requests between clients and server" \
 
 #define diff_trivial_usage \
        "[-abdiNqrTstw] [-L LABEL] [-S FILE] [-U LINES] FILE1 FILE2"
diff --git a/networking/udhcp/dhcprelay.c b/networking/udhcp/dhcprelay.c
index f3b2855d8..53540d1ab 100644
--- a/networking/udhcp/dhcprelay.c
+++ b/networking/udhcp/dhcprelay.c
@@ -13,7 +13,6 @@
 #include "common.h"
 #include "options.h"
 
-/* constants */
 #define SERVER_PORT      67
 #define SELECT_TIMEOUT    5 /* select timeout in sec. */
 #define MAX_LIFETIME   2*60 /* lifetime of an xid entry in sec. */
@@ -149,19 +148,21 @@ static char **get_client_devices(char *dev_list, int *client_number)
 }
 
 
-/* Creates listen sockets (in fds) and returns numerically max fd. */
-static int init_sockets(char **client, int num_clients,
-                        char *server, int *fds)
+/* Creates listen sockets (in fds) bound to client and server ifaces,
+ * and returns numerically max fd.
+ */
+static int init_sockets(char **client_ifaces, int num_clients,
+                        char *server_iface, int *fds)
 {
         int i, n;
 
         /* talk to real server on bootps */
-        fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server);
+        fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server_iface);
         n = fds[0];
 
         for (i = 1; i < num_clients; i++) {
                 /* listen for clients on bootps */
-                fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, client[i-1]);
+                fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, client_ifaces[i-1]);
                 if (fds[i] > n)
                         n = fds[i];
         }
@@ -170,11 +171,11 @@ static int init_sockets(char **client, int num_clients,
 
 
 /**
- * pass_on() - forwards dhcp packets from client to server
+ * pass_to_server() - forwards dhcp packets from client to server
  * p - packet to send
  * client - number of the client
  */
-static void pass_on(struct dhcpMessage *p, int packet_len, int client, int *fds,
+static void pass_to_server(struct dhcpMessage *p, int packet_len, int client, int *fds,
                         struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
 {
         int res, type;
@@ -193,19 +194,19 @@ static void pass_on(struct dhcpMessage *p, int packet_len, int client, int *fds,
         item = xid_add(p->xid, client_addr, client);
 
         /* forward request to LAN (server) */
+        errno = 0;
         res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
                         sizeof(struct sockaddr_in));
         if (res != packet_len) {
-                bb_perror_msg("pass_on");
-                return;
+                bb_perror_msg("sendto");
         }
 }
 
 /**
- * pass_back() - forwards dhcp packets from server to client
+ * pass_to_client() - forwards dhcp packets from server to client
  * p - packet to send
  */
-static void pass_back(struct dhcpMessage *p, int packet_len, int *fds)
+static void pass_to_client(struct dhcpMessage *p, int packet_len, int *fds)
 {
         int res, type;
         struct xid_item *item;
@@ -224,10 +225,11 @@ static void pass_back(struct dhcpMessage *p, int packet_len, int *fds)
 
         if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
                 item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
-        res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip),
-                                sizeof(item->ip));
+        errno = 0;
+        res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip),
+                        sizeof(item->ip));
         if (res != packet_len) {
-                bb_perror_msg("pass_back");
+                bb_perror_msg("sendto");
                 return;
         }
 
@@ -235,20 +237,53 @@ static void pass_back(struct dhcpMessage *p, int packet_len, int *fds)
         xid_del(p->xid);
 }
 
-static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients,
-                struct sockaddr_in *server_addr, uint32_t gw_ip) NORETURN;
-static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients,
-                struct sockaddr_in *server_addr, uint32_t gw_ip)
+int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int dhcprelay_main(int argc, char **argv)
 {
         struct dhcpMessage dhcp_msg;
-        fd_set rfds;
-        size_t packlen;
-        socklen_t addr_size;
+        struct sockaddr_in server_addr;
         struct sockaddr_in client_addr;
-        struct timeval tv;
-        int i;
+        fd_set rfds;
+        char **client_ifaces;
+        int *fds;
+        int num_sockets, max_socket;
+        uint32_t our_ip;
+
+        server_addr.sin_family = AF_INET;
+        server_addr.sin_port = htons(SERVER_PORT);
+
+        /* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */
+        if (argc == 4) {
+                if (!inet_aton(argv[3], &server_addr.sin_addr))
+                        bb_perror_msg_and_die("bad server IP");
+        } else if (argc == 3) {
+                server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
+        } else {
+                bb_show_usage();
+        }
+
+        /* Produce list of client ifaces */
+        client_ifaces = get_client_devices(argv[1], &num_sockets);
+
+        num_sockets++; /* for server socket at fds[0] */
+        fds = xmalloc(num_sockets * sizeof(fds[0]));
+
+        /* Create sockets and bind one to every iface */
+        max_socket = init_sockets(client_ifaces, num_sockets, argv[2], fds);
+
+        /* Get our IP on server_iface */
+        if (udhcp_read_interface(argv[2], NULL, &our_ip, NULL))
+                return 1;
 
+        /* Main loop */
         while (1) {
+//reinit stuff from time to time? go back to get_client_devices
+//every N minutes?
+                struct timeval tv;
+                size_t packlen;
+                socklen_t addr_size;
+                int i;
+
                 FD_ZERO(&rfds);
                 for (i = 0; i < num_sockets; i++)
                         FD_SET(fds[i], &rfds);
@@ -259,56 +294,32 @@ static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **cli
                         if (FD_ISSET(fds[0], &rfds)) {
                                 packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
                                 if (packlen > 0) {
-                                        pass_back(&dhcp_msg, packlen, fds);
+                                        pass_to_client(&dhcp_msg, packlen, fds);
                                 }
                         }
+                        /* clients */
                         for (i = 1; i < num_sockets; i++) {
-                                /* clients */
                                 if (!FD_ISSET(fds[i], &rfds))
                                         continue;
                                 addr_size = sizeof(struct sockaddr_in);
                                 packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
-                                                        (struct sockaddr *)(&client_addr), &addr_size);
+                                                (struct sockaddr *)(&client_addr), &addr_size);
                                 if (packlen <= 0)
                                         continue;
-                                if (udhcp_read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL))
-                                        dhcp_msg.giaddr = gw_ip;
-                                pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr);
+
+                                /* Get our IP on corresponding client_iface */
+//why? what if server can't route such IP?
+                                if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.giaddr, NULL)) {
+                                        /* Fall back to our server_iface's IP */
+//this makes more sense!
+                                        dhcp_msg.giaddr = our_ip;
+                                }
+//maybe set dhcp_msg.flags |= BROADCAST_FLAG too?
+                                pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
                         }
                 }
                 xid_expire();
-        }
-}
-
-int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int dhcprelay_main(int argc, char **argv)
-{
-        int num_sockets, max_socket;
-        int *fds;
-        uint32_t gw_ip;
-        char **clients;
-        struct sockaddr_in server_addr;
-
-        server_addr.sin_family = AF_INET;
-        server_addr.sin_port = htons(SERVER_PORT);
-        if (argc == 4) {
-                if (!inet_aton(argv[3], &server_addr.sin_addr))
-                        bb_perror_msg_and_die("didn't grok server");
-        } else if (argc == 3) {
-                server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
-        } else {
-                bb_show_usage();
-        }
-
-        clients = get_client_devices(argv[1], &num_sockets);
-        num_sockets++; /* for server socket at fds[0] */
-        fds = xmalloc(num_sockets * sizeof(fds[0]));
-        max_socket = init_sockets(clients, num_sockets, argv[2], fds);
-
-        if (udhcp_read_interface(argv[2], NULL, &gw_ip, NULL))
-                return 1;
+        } /* while (1) */
 
-        /* doesn't return */
-        dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);
         /* return 0; - not reached */
 }