udhcp: abort if we see unknown option, and show valid options if so

function                                             old     new   delta
udhcp_option_idx                                       -      77     +77
udhcp_str2optset                                     366     351     -15
udhcpc_main                                         2845    2801     -44
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/2 up/down: 77/-59)             Total: 18 bytes

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

networking/udhcp/common.c

@@ -146,6 +146,25 @@ static void log_option(const char *pfx, const uint8_t *opt)
 # define log_option(pfx, opt) ((void)0)
 #endif
 
+unsigned FAST_FUNC udhcp_option_idx(const char *name)
+{
+	int n = index_in_strings(dhcp_option_strings, name);
+	if (n >= 0)
+		return n;
+
+	{
+		char buf[sizeof(dhcp_option_strings)];
+		char *d = buf;
+		const char *s = dhcp_option_strings;
+		while (s < dhcp_option_strings + sizeof(dhcp_option_strings) - 2) {
+			*d++ = (*s == '\0' ? ' ' : *s);
+			s++;
+		}
+		*d = '\0';
+		bb_error_msg_and_die("unknown option '%s', known options: %s", name, buf);
+	}
+}
+
 /* get an option with bounds checking (warning, result is not aligned). */
 uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
 {
@@ -372,7 +391,7 @@ int FAST_FUNC udhcp_str2optset(const char *const_str, void *arg)
 	char *opt, *val, *endptr;
 	char *str;
 	const struct dhcp_option *option;
-	int retval, length, idx;
+	int retval, length;
 	char buffer[8] ALIGNED(4);
 	uint16_t *result_u16 = (uint16_t *) buffer;
 	uint32_t *result_u32 = (uint32_t *) buffer;
@@ -383,10 +402,7 @@ int FAST_FUNC udhcp_str2optset(const char *const_str, void *arg)
 	if (!opt)
 		return 0;
 
-	idx = index_in_strings(dhcp_option_strings, opt); /* NB: was strcasecmp! */
+	option = &dhcp_options[udhcp_option_idx(opt)];
-	if (idx < 0)
-		return 0;
-	option = &dhcp_options[idx];
 
 	retval = 0;
 	do {

networking/udhcp/common.h

@@ -169,6 +169,8 @@ extern const struct dhcp_option dhcp_options[];
 extern const char dhcp_option_strings[];
 extern const uint8_t dhcp_option_lengths[];
 
+unsigned FAST_FUNC udhcp_option_idx(const char *name);
+
 uint8_t *udhcp_get_option(struct dhcp_packet *packet, int code) FAST_FUNC;
 int udhcp_end_option(uint8_t *optionptr) FAST_FUNC;
 void udhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt) FAST_FUNC;

networking/udhcp/dhcpc.c

@@ -879,21 +879,17 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		client_config.no_default_options = 1;
 	while (list_O) {
 		char *optstr = llist_pop(&list_O);
-		int n = index_in_strings(dhcp_option_strings, optstr);
+		unsigned n = udhcp_option_idx(optstr);
-		if (n < 0)
-			bb_error_msg_and_die("unknown option '%s'", optstr);
 		n = dhcp_options[n].code;
 		client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 	}
 	while (list_x) {
-		int n;
+		unsigned n;
 		char *optstr = llist_pop(&list_x);
 		char *colon = strchr(optstr, ':');
 		if (colon)
 			*colon = '\0';
-		n = index_in_strings(dhcp_option_strings, optstr);
+		n = udhcp_option_idx(optstr);
-		if (n < 0)
-			bb_error_msg_and_die("unknown option '%s'", optstr);
 		if (colon)
 			*colon = ' ';
 		udhcp_str2optset(optstr, &client_config.options);