Merge commit '06f719fd79fe15ce6fd5431bc58fcb22851de24d^'

8 files changed, 301 insertions, 82 deletions

diff --git a/networking/Config.src b/networking/Config.src
index 9fc122bf3..6dd7df754 100644
--- a/networking/Config.src
+++ b/networking/Config.src
@@ -804,7 +804,7 @@ config TELNETD
 
                   mount -t devpts devpts /dev/pts
 
-          You need to be sure that Busybox has LOGIN and
+          You need to be sure that busybox has LOGIN and
           FEATURE_SUID enabled. And finally, you should make
           certain that Busybox has been installed setuid root:
 
diff --git a/networking/nbd-client.c b/networking/nbd-client.c
new file mode 100644
index 000000000..5ac190c32
--- /dev/null
+++ b/networking/nbd-client.c
@@ -0,0 +1,153 @@
+/*
+ * Copyright 2010 Rob Landley <rob@landley.net>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+#include "libbb.h"
+#include <netinet/tcp.h>
+#include <linux/fs.h>
+
+//applet:IF_NBDCLIENT(APPLET_ODDNAME(nbd-client, nbdclient, _BB_DIR_USR_SBIN, _BB_SUID_DROP, nbdclient))
+
+//kbuild:lib-$(CONFIG_NBDCLIENT) += nbd-client.o
+
+//config:config NBDCLIENT
+//config:       bool "nbd-client"
+//config:       default y
+//config:       help
+//config:         Network block device client
+
+#define NBD_SET_SOCK          _IO(0xab, 0)
+#define NBD_SET_BLKSIZE       _IO(0xab, 1)
+#define NBD_SET_SIZE          _IO(0xab, 2)
+#define NBD_DO_IT             _IO(0xab, 3)
+#define NBD_CLEAR_SOCK        _IO(0xab, 4)
+#define NBD_CLEAR_QUEUE       _IO(0xab, 5)
+#define NBD_PRINT_DEBUG       _IO(0xab, 6)
+#define NBD_SET_SIZE_BLOCKS   _IO(0xab, 7)
+#define NBD_DISCONNECT        _IO(0xab, 8)
+#define NBD_SET_TIMEOUT       _IO(0xab, 9)
+
+//usage:#define nbdclient_trivial_usage
+//usage:       "HOST PORT BLOCKDEV"
+//usage:#define nbdclient_full_usage "\n\n"
+//usage:       "Connect to HOST and provide a network block device on BLOCKDEV"
+
+//TODO: more compat with nbd-client version 2.9.13 -
+//Usage: nbd-client [bs=blocksize] [timeout=sec] host port nbd_device [-swap] [-persist] [-nofork]
+//Or   : nbd-client -d nbd_device
+//Or   : nbd-client -c nbd_device
+//Default value for blocksize is 1024 (recommended for ethernet)
+//Allowed values for blocksize are 512,1024,2048,4096
+//Note, that kernel 2.4.2 and older ones do not work correctly with
+//blocksizes other than 1024 without patches
+
+int nbdclient_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int nbdclient_main(int argc, char **argv)
+{
+        unsigned long timeout = 0;
+        int nofork = 0;
+        char *host, *port, *device;
+        struct nbd_header_t {
+                uint64_t magic1; // "NBDMAGIC"
+                uint64_t magic2; // 0x420281861253 big endian
+                uint64_t devsize;
+                uint32_t flags;
+                char data[124];
+        } nbd_header;
+        struct bug_check {
+                char c[offsetof(struct nbd_header_t, data) == 8+8+8+4 ? 1 : -1];
+        };
+
+        // Parse command line stuff (just a stub now)
+        if (argc != 4)
+                bb_show_usage();
+
+#if !BB_MMU
+        bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
+#endif
+
+        host = argv[1];
+        port = argv[2];
+        device = argv[3];
+
+        // Repeat until spanked (-persist behavior)
+        for (;;) {
+                int sock, nbd;
+                int ro;
+
+                // Make sure the /dev/nbd exists
+                nbd = xopen(device, O_RDWR);
+
+                // Find and connect to server
+                sock = create_and_connect_stream_or_die(host, xatou16(port));
+                setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &const_int_1, sizeof(const_int_1));
+
+                // Log on to the server
+                xread(sock, &nbd_header, 8+8+8+4 + 124);
+                if (memcmp(&nbd_header.magic1, "NBDMAGIC""\x00\x00\x42\x02\x81\x86\x12\x53", 16) != 0)
+                        bb_error_msg_and_die("login failed");
+
+                // Set 4k block size.  Everything uses that these days
+                ioctl(nbd, NBD_SET_BLKSIZE, 4096);
+                ioctl(nbd, NBD_SET_SIZE_BLOCKS, SWAP_BE64(nbd_header.devsize) / 4096);
+                ioctl(nbd, NBD_CLEAR_SOCK);
+
+                // If the sucker was exported read only, respect that locally
+                ro = (nbd_header.flags & SWAP_BE32(2)) / SWAP_BE32(2);
+                if (ioctl(nbd, BLKROSET, &ro) < 0)
+                        bb_perror_msg_and_die("BLKROSET");
+
+                if (timeout)
+                        if (ioctl(nbd, NBD_SET_TIMEOUT, timeout))
+                                bb_perror_msg_and_die("NBD_SET_TIMEOUT");
+                if (ioctl(nbd, NBD_SET_SOCK, sock))
+                        bb_perror_msg_and_die("NBD_SET_SOCK");
+
+                // if (swap) mlockall(MCL_CURRENT|MCL_FUTURE);
+
+#if BB_MMU
+                // Open the device to force reread of the partition table.
+                // Need to do it in a separate process, since open(device)
+                // needs some other process to sit in ioctl(nbd, NBD_DO_IT).
+                if (fork() == 0) {
+                        char *s = strrchr(device, '/');
+                        sprintf(nbd_header.data, "/sys/block/%.32s/pid", s ? s + 1 : device);
+                        // Is it up yet?
+                        for (;;) {
+                                int fd = open(nbd_header.data, O_RDONLY);
+                                if (fd >= 0) {
+                                        //close(fd);
+                                        break;
+                                }
+                                sleep(1);
+                        }
+                        open(device, O_RDONLY);
+                        return 0;
+                }
+
+                // Daemonize here
+                if (!nofork) {
+                        daemon(0, 0);
+                        nofork = 1;
+                }
+#endif
+
+                // This turns us (the process that calls this ioctl)
+                // into a dedicated NBD request handler.
+                // We block here for a long time.
+                // When exactly ioctl returns? On a signal,
+                // or if someone does ioctl(NBD_DISCONNECT) [nbd-client -d].
+                if (ioctl(nbd, NBD_DO_IT) >= 0 || errno == EBADR) {
+                        // Flush queue and exit
+                        ioctl(nbd, NBD_CLEAR_QUEUE);
+                        ioctl(nbd, NBD_CLEAR_SOCK);
+                        break;
+                }
+
+                close(sock);
+                close(nbd);
+        }
+
+        return 0;
+}
diff --git a/networking/nc_bloaty.c b/networking/nc_bloaty.c
index 6b5b176c9..8594a67a6 100644
--- a/networking/nc_bloaty.c
+++ b/networking/nc_bloaty.c
@@ -57,7 +57,8 @@
 //usage:#define nc_trivial_usage
 //usage:       "[OPTIONS] HOST PORT  - connect"
 //usage:        IF_NC_SERVER("\n"
-//usage:       "nc [OPTIONS] -l -p PORT [HOST] [PORT]  - listen")
+//usage:       "nc [OPTIONS] -l -p PORT [HOST] [PORT]  - listen"
+//usage:        )
 //usage:#define nc_full_usage "\n\n"
 //usage:       "Options:"
 //usage:     "\n        -e PROG Run PROG after connect (must be last)"
diff --git a/networking/ntpd.c b/networking/ntpd.c
index 6707e9bdb..ca4afa045 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -1765,6 +1765,10 @@ recv_and_process_client_pkt(void /*int fd*/)
         /* this time was obtained between poll() and recv() */
         msg.m_rectime = d_to_lfp(G.cur_time);
         msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */
+        if (G.peer_cnt == 0) {
+                /* we have no peers: "stratum 1 server" mode. reftime = our own time */
+                G.reftime = G.cur_time;
+        }
         msg.m_reftime = d_to_lfp(G.reftime);
         msg.m_orgtime = query_xmttime;
         msg.m_rootdelay = d_to_sfp(G.rootdelay);
@@ -1902,8 +1906,13 @@ static NOINLINE void ntp_init(char **argv)
                 bb_show_usage();
 //      if (opts & OPT_x) /* disable stepping, only slew is allowed */
 //              G.time_was_stepped = 1;
-        while (peers)
-                add_peers(llist_pop(&peers));
+        if (peers) {
+                while (peers)
+                        add_peers(llist_pop(&peers));
+        } else {
+                /* -l but no peers: "stratum 1 server" mode */
+                G.stratum = 1;
+        }
         if (!(opts & OPT_n)) {
                 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
                 logmode = LOGMODE_NONE;
diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
index 97ab4cdbb..b6b274d91 100644
--- a/networking/udhcp/common.c
+++ b/networking/udhcp/common.c
@@ -37,6 +37,7 @@ const struct dhcp_optflag dhcp_optflags[] = {
         { OPTION_U8                               , 0x17 }, /* DHCP_IP_TTL        */
         { OPTION_U16                              , 0x1a }, /* DHCP_MTU           */
         { OPTION_IP                   | OPTION_REQ, 0x1c }, /* DHCP_BROADCAST     */
+        { OPTION_IP_PAIR | OPTION_LIST            , 0x21 }, /* DHCP_ROUTES        */
         { OPTION_STRING                           , 0x28 }, /* DHCP_NIS_DOMAIN    */
         { OPTION_IP | OPTION_LIST                 , 0x29 }, /* DHCP_NIS_SERVER    */
         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x2a }, /* DHCP_NTP_SERVER    */
@@ -54,6 +55,7 @@ const struct dhcp_optflag dhcp_optflags[] = {
         { OPTION_SIP_SERVERS                      , 0x78 }, /* DHCP_SIP_SERVERS   */
 #endif
         { OPTION_STATIC_ROUTES                    , 0x79 }, /* DHCP_STATIC_ROUTES */
+        { OPTION_STATIC_ROUTES                    , 0xf9 }, /* DHCP_MS_STATIC_ROUTES */
         { OPTION_STRING                           , 0xfc }, /* DHCP_WPAD          */
 
         /* Options below have no match in dhcp_option_strings[],
@@ -95,6 +97,7 @@ const char dhcp_option_strings[] ALIGN1 =
         "ipttl" "\0"       /* DHCP_IP_TTL         */
         "mtu" "\0"         /* DHCP_MTU            */
         "broadcast" "\0"   /* DHCP_BROADCAST      */
+        "routes" "\0"      /* DHCP_ROUTES         */
         "nisdomain" "\0"   /* DHCP_NIS_DOMAIN     */
         "nissrv" "\0"      /* DHCP_NIS_SERVER     */
         "ntpsrv" "\0"      /* DHCP_NTP_SERVER     */
@@ -114,6 +117,7 @@ const char dhcp_option_strings[] ALIGN1 =
 // doesn't work in udhcpd.conf since OPTION_STATIC_ROUTES
 // is not handled yet by "string->option" conversion code:
         "staticroutes" "\0"/* DHCP_STATIC_ROUTES  */
+        "msstaticroutes""\0"/* DHCP_MS_STATIC_ROUTES */
         "wpad" "\0"        /* DHCP_WPAD           */
         ;
 
diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index c5abf17d5..9020b9c96 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -123,6 +123,7 @@ enum {
 //#define DHCP_IP_TTL           0x17
 //#define DHCP_MTU              0x1a
 //#define DHCP_BROADCAST        0x1c
+//#define DHCP_ROUTES           0x21
 //#define DHCP_NIS_DOMAIN       0x28
 //#define DHCP_NIS_SERVER       0x29
 //#define DHCP_NTP_SERVER       0x2a
@@ -144,6 +145,7 @@ enum {
 //#define DHCP_DOMAIN_SEARCH    0x77 /* RFC 3397. set of ASCIZ string, DNS-style compressed */
 //#define DHCP_SIP_SERVERS      0x78 /* RFC 3361. flag byte, then: 0: domain names, 1: IP addrs */
 //#define DHCP_STATIC_ROUTES    0x79 /* RFC 3442. (mask,ip,router) tuples */
+//#define DHCP_MS_STATIC_ROUTES 0xf9 /* Microsoft's pre-RFC 3442 code for 0x79? */
 //#define DHCP_WPAD             0xfc /* MSIE's Web Proxy Autodiscovery Protocol */
 #define DHCP_END                0xff
 
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index de1b79844..27d6ad1a8 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -89,6 +89,7 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
 
         /* option points to OPT_DATA, need to go back and get OPT_LEN */
         len = option[OPT_LEN - OPT_DATA];
+
         type = optflag->flags & OPTION_TYPE_MASK;
         optlen = dhcp_option_lengths[type];
         upper_length = len_of_option_as_string[type] * ((unsigned)len / (unsigned)optlen);
@@ -97,17 +98,16 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
         dest += sprintf(ret, "%s=", opt_name);
 
         while (len >= optlen) {
+                unsigned ip_ofs = 0;
+
                 switch (type) {
                 case OPTION_IP_PAIR:
                         dest += sprint_nip(dest, "", option);
                         *dest++ = '/';
-                        option += 4;
-                        optlen = 4;
+                        ip_ofs = 4;
+                        /* fall through */
                 case OPTION_IP:
-                        dest += sprint_nip(dest, "", option);
-// TODO: it can be a list only if (optflag->flags & OPTION_LIST).
-// Should we bail out/warn if we see multi-ip option which is
-// not allowed to be such? For example, DHCP_BROADCAST...
+                        dest += sprint_nip(dest, "", option + ip_ofs);
                         break;
 //              case OPTION_BOOLEAN:
 //                      dest += sprintf(dest, *option ? "yes" : "no");
@@ -218,7 +218,10 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
                 } /* switch */
                 option += optlen;
                 len -= optlen;
-                if (len <= 0)
+// TODO: it can be a list only if (optflag->flags & OPTION_LIST).
+// Should we bail out/warn if we see multi-ip option which is
+// not allowed to be such (for example, DHCP_BROADCAST)? -
+                if (len <= 0 /* || !(optflag->flags & OPTION_LIST) */)
                         break;
                 *dest++ = ' ';
                 *dest = '\0';
diff --git a/networking/udhcp/dhcprelay.c b/networking/udhcp/dhcprelay.c
index a2c7f359d..759a4ba03 100644
--- a/networking/udhcp/dhcprelay.c
+++ b/networking/udhcp/dhcprelay.c
@@ -11,9 +11,12 @@
  */
 #include "common.h"
 
-#define SERVER_PORT      67
-#define SELECT_TIMEOUT    5 /* select timeout in sec. */
-#define MAX_LIFETIME   2*60 /* lifetime of an xid entry in sec. */
+#define SERVER_PORT    67
+
+/* lifetime of an xid entry in sec. */
+#define MAX_LIFETIME   2*60
+/* select timeout in sec. */
+#define SELECT_TIMEOUT (MAX_LIFETIME / 8)
 
 /* This list holds information about clients. The xid_* functions manipulate this list. */
 struct xid_item {
@@ -67,11 +70,11 @@ static struct xid_item *xid_find(uint32_t xid)
         struct xid_item *item = dhcprelay_xid_list.next;
         while (item != NULL) {
                 if (item->xid == xid) {
-                        return item;
+                        break;
                 }
                 item = item->next;
         }
-        return NULL;
+        return item;
 }
 
 static void xid_del(uint32_t xid)
@@ -110,62 +113,72 @@ static int get_dhcp_packet_type(struct dhcp_packet *p)
 }
 
 /**
- * get_client_devices - parses the devices list
- * dev_list - comma separated list of devices
+ * make_iface_list - parses client/server interface names
  * returns array
  */
-static char **get_client_devices(char *dev_list, int *client_number)
+static char **make_iface_list(char **client_and_server_ifaces, int *client_number)
 {
-        char *s, **client_dev;
+        char *s, **iface_list;
         int i, cn;
 
-        /* copy list */
-        dev_list = xstrdup(dev_list);
-
-        /* get number of items, replace ',' with NULs */
-        s = dev_list;
-        cn = 1;
+        /* get number of items */
+        cn = 2; /* 1 server iface + at least 1 client one */
+        s = client_and_server_ifaces[0]; /* list of client ifaces */
         while (*s) {
-                if (*s == ',') {
-                        *s = '\0';
+                if (*s == ',')
                         cn++;
-                }
                 s++;
         }
         *client_number = cn;
 
         /* create vector of pointers */
-        client_dev = xzalloc(cn * sizeof(*client_dev));
-        client_dev[0] = dev_list;
+        iface_list = xzalloc(cn * sizeof(iface_list[0]));
+
+        iface_list[0] = client_and_server_ifaces[1]; /* server iface */
+
         i = 1;
-        while (i != cn) {
-                client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
-                i++;
+        s = xstrdup(client_and_server_ifaces[0]); /* list of client ifaces */
+        goto store_client_iface_name;
+
+        while (i < cn) {
+                if (*s++ == ',') {
+                        s[-1] = '\0';
+ store_client_iface_name:
+                        iface_list[i++] = s;
+                }
         }
-        return client_dev;
+
+        return iface_list;
 }
 
 /* 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)
+static int init_sockets(char **iface_list, int num_clients, int *fds)
 {
         int i, n;
 
-        /* talk to real server on bootps */
-        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_ifaces[i-1]);
-                if (fds[i] > n)
+        n = 0;
+        for (i = 0; i < num_clients; i++) {
+                fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, iface_list[i]);
+                if (n < fds[i])
                         n = fds[i];
         }
         return n;
 }
 
+static int sendto_ip4(int sock, const void *msg, int msg_len, struct sockaddr_in *to)
+{
+        int err;
+
+        errno = 0;
+        err = sendto(sock, msg, msg_len, 0, (struct sockaddr*) to, sizeof(*to));
+        err -= msg_len;
+        if (err)
+                bb_perror_msg("sendto");
+        return err;
+}
+
 /**
  * pass_to_server() - forwards dhcp packets from client to server
  * p - packet to send
@@ -174,7 +187,7 @@ static int init_sockets(char **client_ifaces, int num_clients,
 static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, int *fds,
                         struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
 {
-        int res, type;
+        int type;
 
         /* check packet_type */
         type = get_dhcp_packet_type(p);
@@ -188,13 +201,12 @@ static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, in
         /* create new xid entry */
         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("sendto");
-        }
+        /* forward request to server */
+        /* note that we send from fds[0] which is bound to SERVER_PORT (67).
+         * IOW: we send _from_ SERVER_PORT! Although this may look strange,
+         * RFC 1542 not only allows, but prescribes this for BOOTP relays.
+         */
+        sendto_ip4(fds[0], p, packet_len, server_addr);
 }
 
 /**
@@ -203,7 +215,7 @@ static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, in
  */
 static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
 {
-        int res, type;
+        int type;
         struct xid_item *item;
 
         /* check xid */
@@ -218,14 +230,12 @@ static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
                 return;
         }
 
+//TODO: also do it if (p->flags & htons(BROADCAST_FLAG)) is set!
         if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
                 item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
-        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("sendto");
-                return;
+
+        if (sendto_ip4(fds[item->client], p, packet_len, &item->ip) != 0) {
+                return; /* send error occurred */
         }
 
         /* remove xid entry */
@@ -235,36 +245,30 @@ static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
 int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int dhcprelay_main(int argc, char **argv)
 {
-        struct dhcp_packet dhcp_msg;
         struct sockaddr_in server_addr;
-        struct sockaddr_in client_addr;
-        fd_set rfds;
-        char **client_ifaces;
+        char **iface_list;
         int *fds;
         int num_sockets, max_socket;
         uint32_t our_nip;
 
         server_addr.sin_family = AF_INET;
+        server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
         server_addr.sin_port = htons(SERVER_PORT);
 
-        /* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */
+        /* 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 {
+        } else if (argc != 3) {
                 bb_show_usage();
         }
 
-        /* Produce list of client ifaces */
-        client_ifaces = get_client_devices(argv[1], &num_sockets);
+        iface_list = make_iface_list(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);
+        max_socket = init_sockets(iface_list, num_sockets, fds);
 
         /* Get our IP on server_iface */
         if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
@@ -272,11 +276,10 @@ int dhcprelay_main(int argc, char **argv)
 
         /* Main loop */
         while (1) {
-//reinit stuff from time to time? go back to get_client_devices
-//every N minutes?
+// reinit stuff from time to time? go back to make_iface_list
+// every N minutes?
+                fd_set rfds;
                 struct timeval tv;
-                size_t packlen;
-                socklen_t addr_size;
                 int i;
 
                 FD_ZERO(&rfds);
@@ -285,6 +288,9 @@ int dhcprelay_main(int argc, char **argv)
                 tv.tv_sec = SELECT_TIMEOUT;
                 tv.tv_usec = 0;
                 if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
+                        int packlen;
+                        struct dhcp_packet dhcp_msg;
+
                         /* server */
                         if (FD_ISSET(fds[0], &rfds)) {
                                 packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
@@ -292,24 +298,65 @@ int dhcprelay_main(int argc, char **argv)
                                         pass_to_client(&dhcp_msg, packlen, fds);
                                 }
                         }
+
                         /* clients */
                         for (i = 1; i < num_sockets; i++) {
+                                struct sockaddr_in client_addr;
+                                socklen_t addr_size;
+
                                 if (!FD_ISSET(fds[i], &rfds))
                                         continue;
-                                addr_size = sizeof(struct sockaddr_in);
+
+                                addr_size = sizeof(client_addr);
                                 packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
                                                 (struct sockaddr *)(&client_addr), &addr_size);
                                 if (packlen <= 0)
                                         continue;
 
                                 /* 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.gateway_nip, NULL)) {
-                                        /* Fall back to our server_iface's IP */
-//this makes more sense!
+// RFC 1542
+// 4.1 General BOOTP Processing for Relay Agents
+// 4.1.1 BOOTREQUEST Messages
+//   If the relay agent does decide to relay the request, it MUST examine
+//   the 'giaddr' ("gateway" IP address) field.  If this field is zero,
+//   the relay agent MUST fill this field with the IP address of the
+//   interface on which the request was received.  If the interface has
+//   more than one IP address logically associated with it, the relay
+//   agent SHOULD choose one IP address associated with that interface and
+//   use it consistently for all BOOTP messages it relays.  If the
+//   'giaddr' field contains some non-zero value, the 'giaddr' field MUST
+//   NOT be modified.  The relay agent MUST NOT, under any circumstances,
+//   fill the 'giaddr' field with a broadcast address as is suggested in
+//   [1] (Section 8, sixth paragraph).
+
+// but why? what if server can't route such IP? Client ifaces may be, say, NATed!
+
+// 4.1.2 BOOTREPLY Messages
+//   BOOTP relay agents relay BOOTREPLY messages only to BOOTP clients.
+//   It is the responsibility of BOOTP servers to send BOOTREPLY messages
+//   directly to the relay agent identified in the 'giaddr' field.
+// (yeah right, unless it is impossible... see comment above)
+//   Therefore, a relay agent may assume that all BOOTREPLY messages it
+//   receives are intended for BOOTP clients on its directly-connected
+//   networks.
+//
+//   When a relay agent receives a BOOTREPLY message, it should examine
+//   the BOOTP 'giaddr', 'yiaddr', 'chaddr', 'htype', and 'hlen' fields.
+//   These fields should provide adequate information for the relay agent
+//   to deliver the BOOTREPLY message to the client.
+//
+//   The 'giaddr' field can be used to identify the logical interface from
+//   which the reply must be sent (i.e., the host or router interface
+//   connected to the same network as the BOOTP client).  If the content
+//   of the 'giaddr' field does not match one of the relay agent's
+//   directly-connected logical interfaces, the BOOTREPLY messsage MUST be
+//   silently discarded.
+                                if (udhcp_read_interface(iface_list[i], NULL, &dhcp_msg.gateway_nip, NULL)) {
+                                        /* Fall back to our IP on server iface */
+// this makes more sense!
                                         dhcp_msg.gateway_nip = our_nip;
                                 }
-//maybe set dhcp_msg.flags |= BROADCAST_FLAG too?
+// maybe dhcp_msg.hops++? drop packets with too many hops (RFC 1542 says 4 or 16)?
                                 pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
                         }
                 }