lua: add add_domain function to encode a string using RFC 1035

Author: rsmarples

README.md

@@ -87,6 +87,7 @@ local dhcp_opts = {
 	['MTU'] = 26,
 	['PARAMETERREQUESTLIST'] = 55,
 	['FQDN'] = 81,
+	['DOMAINSEARCH'] = 119,
 }
 
 -- Checks if the client requested the DHCP option or not.
@@ -181,6 +182,7 @@ end
 -- dhcpsd will call this function to add options to a DHCP reply.
 -- The dhcp table adds the following functions:
 --     add_ip, add_string, add_uint32, add_uint16 and add_uint8
+--     add_domain
 --     set_bootp_file, set_bootp_sname
 -- Return non zero to stop other plugins applying options.
 function add_dhcp_options(hostname, htype, chaddr)
@@ -193,6 +195,12 @@ function add_dhcp_options(hostname, htype, chaddr)
 	if has_parameter_request(dhcp_opts['DNSSERVER']) then
 		dhcp.add_ip(dhcp_opts['DNSSERVER'], '10.73.1.1, 10.73.1.2')
 	end
+	if has_parameter_request(dhcp_opts['DNSDOMAIN']) then
+		dhcp.add_string(dhcp_opts['DNSDOMAIN'], domain)
+	end
+	if has_parameter_request(dhcp_opts['DOMAINSEARCH']) then
+		dhcp.add_domain(dhcp_opts['DOMAINSEARCH'], domain)
+	end
 
     -- If the subnet needs a specific MTU for PPPoE, etc
     -- dhcp.add_uint16(dhcp_opts['MTU'], 1480);

src/dhcp.h

@@ -257,15 +257,17 @@ uint32_t dhcp_atof(const char *);
 		**(p) = (v);                 \
 		*(p) = *(p) + 1;             \
 	} while (0 /* CONSTCOND */)
-#define DHCP_PUT_BIN(p, e, o, v, l)            \
-	do {                                   \
-		DHCP_PUT_CHECK((p), (e), (l)); \
-		**(p) = (o);                   \
-		*(p) = *(p) + 1;               \
-		**(p) = (uint8_t)(l);          \
-		*(p) = *(p) + 1;               \
-		memcpy(*(p), (v), (l));        \
-		*(p) = *(p) + (l);             \
+#define DHCP_PUT_BIN(p, e, o, v, l)             \
+	do {                                    \
+		DHCP_PUT_CHECK((p), (e), (l));  \
+		**(p) = (o);                    \
+		*(p) = *(p) + 1;                \
+		**(p) = (uint8_t)(l);           \
+		*(p) = *(p) + 1;                \
+		if ((l) != 0) {                 \
+			memcpy(*(p), (v), (l)); \
+			*(p) = *(p) + (l);      \
+		}                               \
 	} while (0 /* CONSTCOND */)
 #define DHCP_PUT_U8(p, e, o, v)                                     \
 	do {                                                        \

src/plugins/lua.c

@@ -578,6 +578,39 @@ lua_add_dhcp_string(lua_State *L)
 	return 0;
 }
 
+static int
+lua_add_dhcp_domain(lua_State *L)
+{
+	struct lua_ctx *l = &lua_ctx;
+	long long optn = luaL_checkinteger(L, 1);
+	const char *data = luaL_checkstring(L, 2);
+	uint8_t *val;
+	size_t len;
+
+	if (optn < 1 || optn > 254) {
+		logerrx("%s: option out of range: %lld", lua_name, optn);
+		return 0;
+	}
+
+	if (l->l_p == NULL || l->l_e == NULL) {
+		logerrx("%s: cannot add options", lua_name);
+		return 0;
+	}
+
+	len = encode_rfc1035(data, NULL);
+	if (len == 0)
+		val = NULL;
+	else {
+		val = malloc(len);
+		if (val == NULL)
+			return -1;
+		len = encode_rfc1035(data, val);
+	}
+
+	DHCP_PUT_BIN(&l->l_p, l->l_e, (uint8_t)optn, val, len);
+	return 0;
+}
+
 static ssize_t
 lua_run_add_dhcp_options(struct plugin *p, struct svc_ctx *sctx,
     const void *dhcp, size_t dhcplen)
@@ -779,6 +812,7 @@ lua_init(struct plugin *p)
 		{ "add_uint16", lua_add_dhcp_uint16 },
 		{ "add_uint32", lua_add_dhcp_uint32 },
 		{ "add_string", lua_add_dhcp_string },
+		{ "add_domain", lua_add_dhcp_domain },
 		{ NULL, NULL },
 	};