udhcpc: support for -O <option>.

Two important notes:
* nissrv and nisdomain are not requested by default anymore!
* inconsistency between "XXXsvr" and "XXsrv" in option names resolved,
  all are "XXXsrv" now.

function                                             old     new   delta
udhcpc_main                                         2494    2600    +106
packed_usage                                       23023   23067     +44
add_requests                                          91     119     +28
static.udhcpc_longopts                               209     226     +17
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 195/0)             Total: 195 bytes

1 files changed, 36 insertions, 25 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index d8077f7e8..69c35ca50 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -133,6 +133,7 @@ int udhcpc_main(int argc, char **argv)
 {
         uint8_t *temp, *message;
         char *str_c, *str_V, *str_h, *str_F, *str_r, *str_T, *str_A, *str_t;
+        llist_t *list_O = NULL;
 #if ENABLE_FEATURE_UDHCPC_ARPING
         char *str_W;
 #endif
@@ -183,28 +184,29 @@ int udhcpc_main(int argc, char **argv)
         };
 #if ENABLE_GETOPT_LONG
         static const char udhcpc_longopts[] ALIGN1 =
-                "clientid\0"      Required_argument "c"
-                "clientid-none\0" No_argument       "C"
-                "vendorclass\0"   Required_argument "V"
-                "foreground\0"    No_argument       "f"
-                "background\0"    No_argument       "b"
-                "hostname\0"      Required_argument "H"
-                "fqdn\0"          Required_argument "F"
-                "interface\0"     Required_argument "i"
-                "now\0"           No_argument       "n"
-                "pidfile\0"       Required_argument "p"
-                "quit\0"          No_argument       "q"
-                "release\0"       No_argument       "R"
-                "request\0"       Required_argument "r"
-                "script\0"        Required_argument "s"
-                "timeout\0"       Required_argument "T"
-                "version\0"       No_argument       "v"
-                "retries\0"       Required_argument "t"
-                "tryagain\0"      Required_argument "A"
-                "syslog\0"        No_argument       "S"
+                "clientid\0"       Required_argument "c"
+                "clientid-none\0"  No_argument       "C"
+                "vendorclass\0"    Required_argument "V"
+                "foreground\0"     No_argument       "f"
+                "background\0"     No_argument       "b"
+                "hostname\0"       Required_argument "H"
+                "fqdn\0"           Required_argument "F"
+                "interface\0"      Required_argument "i"
+                "now\0"            No_argument       "n"
+                "pidfile\0"        Required_argument "p"
+                "quit\0"           No_argument       "q"
+                "release\0"        No_argument       "R"
+                "request\0"        Required_argument "r"
+                "script\0"         Required_argument "s"
+                "timeout\0"        Required_argument "T"
+                "version\0"        No_argument       "v"
+                "retries\0"        Required_argument "t"
+                "tryagain\0"       Required_argument "A"
+                "syslog\0"         No_argument       "S"
 #if ENABLE_FEATURE_UDHCPC_ARPING
-                "arping\0"        No_argument       "a"
+                "arping\0"         No_argument       "a"
 #endif
+                "request-option\0" Required_argument "O"
                 ;
 #endif
         /* Default options. */
@@ -212,16 +214,18 @@ int udhcpc_main(int argc, char **argv)
         client_config.script = DEFAULT_SCRIPT;
 
         /* Parse command line */
-        opt_complementary = "c--C:C--c"; // mutually exclusive
+        opt_complementary = "c--C:C--c:O::"; // Cc: mutually exclusive; O: list
 #if ENABLE_GETOPT_LONG
         applet_long_options = udhcpc_longopts;
 #endif
         opt = getopt32(argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:vSA:"
                 USE_FEATURE_UDHCPC_ARPING("aW:")
-                , &str_c, &str_V, &str_h, &str_h, &str_F,
-                &client_config.interface, &client_config.pidfile, &str_r,
-                &client_config.script, &str_T, &str_t, &str_A
+                "O:"
+                , &str_c, &str_V, &str_h, &str_h, &str_F
+                , &client_config.interface, &client_config.pidfile, &str_r
+                , &client_config.script, &str_T, &str_t, &str_A
                 USE_FEATURE_UDHCPC_ARPING(, &str_W)
+                , &list_O
                 );
 
         if (opt & OPT_c)
@@ -268,11 +272,18 @@ int udhcpc_main(int argc, char **argv)
                 puts("version "BB_VER);
                 return 0;
         }
-
         if (opt & OPT_S) {
                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
                 logmode |= LOGMODE_SYSLOG;
         }
+        while (list_O) {
+                int n = index_in_strings(dhcp_option_strings, list_O->data);
+                if (n < 0)
+                        bb_error_msg_and_die("unknown option '%s'", list_O->data);
+                n = dhcp_options[n].code;
+                client_config.opt_mask[n >> 3] |= 1 << (n & 7);
+                list_O = list_O->link;
+        }
 
         if (read_interface(client_config.interface, &client_config.ifindex,
                            NULL, client_config.arp))