udhcpd: support per-client hostnames in static leases

function                                             old     new   delta
read_staticlease                                     222     299     +77
add_server_options                                    92     154     +62
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 139/0)             Total: 139 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 71 insertions, 16 deletions

diff --git a/examples/udhcp/udhcpd.conf b/examples/udhcp/udhcpd.conf
index bb8774e08..df1258aaf 100644
--- a/examples/udhcp/udhcpd.conf
+++ b/examples/udhcp/udhcpd.conf
@@ -44,7 +44,7 @@ interface	eth0
 #notify_file                    # default: no script
 #notify_file    dumpleases      # useful for debugging
 
-# The following are bootp specific options
+# The following are BOOTP specific options
 # next server to use in bootstrap
 #siaddr         192.168.0.22    # default: 0.0.0.0 (none)
 # tftp server name
@@ -52,9 +52,14 @@ interface	eth0
 # tftp file to download (e.g. kernel image)
 #boot_file      /var/nfs_root   # default: none
 
+# NOTE: "boot_file FILE" and "opt bootfile FILE" are conceptually the same,
+# but "boot_file" goes into BOOTP-defined fixed-size field in the packet,
+# whereas "opt bootfile" goes into DHCP option 0x43.
+# Same for "sname HOST" and "opt tftp HOST".
+
 # Static leases map
 #static_lease 00:60:08:11:CE:4E 192.168.0.54
-#static_lease 00:60:08:11:CE:3E 192.168.0.44
+#static_lease 00:60:08:11:CE:3E 192.168.0.44 optional_hostname
 
 # The remainder of options are DHCP options and can be specified with the
 # keyword 'opt' or 'option'. If an option can take multiple items, such
diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index bf44320a1..f231e4001 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -48,14 +48,23 @@
 #define g_leases ((struct dyn_lease*)ptr_to_globals)
 /* struct server_config_t server_config is in bb_common_bufsiz1 */
 
+struct static_lease {
+        struct static_lease *next;
+        uint32_t nip;
+        uint8_t mac[6];
+        uint8_t opt[1];
+};
+
 /* Takes the address of the pointer to the static_leases linked list,
  * address to a 6 byte mac address,
  * 4 byte IP address */
 static void add_static_lease(struct static_lease **st_lease_pp,
                 uint8_t *mac,
-                uint32_t nip)
+                uint32_t nip,
+                const char *opts)
 {
         struct static_lease *st_lease;
+        unsigned optlen;
 
         /* Find the tail of the list */
         while ((st_lease = *st_lease_pp) != NULL) {
@@ -63,10 +72,17 @@ static void add_static_lease(struct static_lease **st_lease_pp,
         }
 
         /* Add new node */
-        *st_lease_pp = st_lease = xzalloc(sizeof(*st_lease));
+        optlen = (opts ? 1+1+strnlen(opts, 120) : 0);
+        *st_lease_pp = st_lease = xzalloc(sizeof(*st_lease) + optlen);
         memcpy(st_lease->mac, mac, 6);
         st_lease->nip = nip;
         /*st_lease->next = NULL;*/
+        if (optlen) {
+                st_lease->opt[OPT_CODE] = DHCP_HOST_NAME;
+                optlen -= 2;
+                st_lease->opt[OPT_LEN] = optlen;
+                memcpy(&st_lease->opt[OPT_DATA], opts, optlen);
+        }
 }
 
 /* Find static lease IP by mac */
@@ -344,6 +360,7 @@ static int FAST_FUNC read_staticlease(const char *const_line, void *arg)
         char *line;
         char *mac_string;
         char *ip_string;
+        char *opts;
         struct ether_addr mac_bytes; /* it's "struct { uint8_t mac[6]; }" */
         uint32_t nip;
 
@@ -358,7 +375,10 @@ static int FAST_FUNC read_staticlease(const char *const_line, void *arg)
         if (!ip_string || !udhcp_str2nip(ip_string, &nip))
                 return 0;
 
-        add_static_lease(arg, (uint8_t*) &mac_bytes, nip);
+        opts = strtok_r(NULL, " \t", &line);
+        /* opts might be NULL, that's not an error */
+
+        add_static_lease(arg, (uint8_t*) &mac_bytes, nip, opts);
 
         log_static_leases(arg);
 
@@ -626,14 +646,49 @@ static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacke
  */
 static void add_server_options(struct dhcp_packet *packet)
 {
-        struct option_set *curr = server_config.options;
+        struct option_set *config_opts;
+        uint8_t *client_hostname_opt;
+
+        client_hostname_opt = NULL;
+        if (packet->yiaddr) { /* if we aren't from send_inform()... */
+                struct static_lease *st_lease = server_config.static_leases;
+                while (st_lease) {
+                        if (st_lease->nip == packet->yiaddr) {
+                                if (st_lease->opt[0] != 0)
+                                        client_hostname_opt = st_lease->opt;
+                                break;
+                        }
+                        st_lease = st_lease->next;
+                }
+        }
 
-        while (curr) {
-                if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
-                        udhcp_add_binary_option(packet, curr->data);
-                curr = curr->next;
+        config_opts = server_config.options;
+        while (config_opts) {
+                if (config_opts->data[OPT_CODE] != DHCP_LEASE_TIME) {
+                        /* ^^^^
+                         * DHCP_LEASE_TIME is already filled, or in case of
+                         * send_inform(), should not be filled at all.
+                         */
+                        if (config_opts->data[OPT_CODE] != DHCP_HOST_NAME
+                         || !client_hostname_opt
+                        ) {
+                                /* Why "!client_hostname_opt":
+                                 * add hostname only if client has no hostname
+                                 * on its static lease line.
+                                 * (Not that "opt hostname HOST"
+                                 * makes much sense in udhcpd.conf,
+                                 * that'd give all clients the same hostname,
+                                 * but it's a valid configuration).
+                                 */
+                                udhcp_add_binary_option(packet, config_opts->data);
+                        }
+                }
+                config_opts = config_opts->next;
         }
 
+        if (client_hostname_opt)
+                udhcp_add_binary_option(packet, client_hostname_opt);
+
         packet->siaddr_nip = server_config.siaddr_nip;
 
         if (server_config.sname)
@@ -753,7 +808,6 @@ static NOINLINE void send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
 
         lease_time_sec = select_lease_time(oldpacket);
         udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
-
         add_server_options(&packet);
 
         addr.s_addr = yiaddr;
diff --git a/networking/udhcp/dhcpd.h b/networking/udhcp/dhcpd.h
index b8f96b029..5c3bf5147 100644
--- a/networking/udhcp/dhcpd.h
+++ b/networking/udhcp/dhcpd.h
@@ -15,11 +15,7 @@ PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
 #define DHCPD_CONF_FILE         "/etc/udhcpd.conf"
 
 
-struct static_lease {
-        struct static_lease *next;
-        uint32_t nip;
-        uint8_t mac[6];
-};
+struct static_lease;
 
 struct server_config_t {
         char *interface;                /* interface to use */