Merge pull request #24019 from yuwata/network-ipv4ll

network: refuse 169.254.0.0/24 and 169.254.255.0/24

src/basic/in-addr-util.c

@@ -49,6 +49,20 @@ bool in4_addr_is_link_local(const struct in_addr *a) {
         return (be32toh(a->s_addr) & UINT32_C(0xFFFF0000)) == (UINT32_C(169) << 24 | UINT32_C(254) << 16);
 }
 
+bool in4_addr_is_link_local_dynamic(const struct in_addr *a) {
+        assert(a);
+
+        if (!in4_addr_is_link_local(a))
+                return false;
+
+        /* 169.254.0.0/24 and 169.254.255.0/24 must not be used for the dynamic IPv4LL assignment.
+         * See RFC 3927 Section 2.1:
+         * The IPv4 prefix 169.254/16 is registered with the IANA for this purpose. The first 256 and last
+         * 256 addresses in the 169.254/16 prefix are reserved for future use and MUST NOT be selected by a
+         * host using this dynamic configuration mechanism. */
+        return !IN_SET(be32toh(a->s_addr) & 0x0000FF00U, 0x0000U, 0xFF00U);
+}
+
 bool in6_addr_is_link_local(const struct in6_addr *a) {
         assert(a);
 

src/basic/in-addr-util.h

@@ -44,6 +44,7 @@ static inline bool in_addr_data_is_set(const struct in_addr_data *a) {
 int in_addr_is_multicast(int family, const union in_addr_union *u);
 
 bool in4_addr_is_link_local(const struct in_addr *a);
+bool in4_addr_is_link_local_dynamic(const struct in_addr *a);
 bool in6_addr_is_link_local(const struct in6_addr *a);
 int in_addr_is_link_local(int family, const union in_addr_union *u);
 bool in6_addr_is_link_local_all_nodes(const struct in6_addr *a);

src/libsystemd-network/sd-ipv4ll.c

@@ -212,21 +212,12 @@ int sd_ipv4ll_is_running(sd_ipv4ll *ll) {
         return sd_ipv4acd_is_running(ll->acd);
 }
 
-static bool ipv4ll_address_is_valid(const struct in_addr *address) {
-        assert(address);
-
-        if (!in4_addr_is_link_local(address))
-                return false;
-
-        return !IN_SET(be32toh(address->s_addr) & 0x0000FF00U, 0x0000U, 0xFF00U);
-}
-
 int sd_ipv4ll_set_address(sd_ipv4ll *ll, const struct in_addr *address) {
         int r;
 
         assert_return(ll, -EINVAL);
         assert_return(address, -EINVAL);
-        assert_return(ipv4ll_address_is_valid(address), -EINVAL);
+        assert_return(in4_addr_is_link_local_dynamic(address), -EINVAL);
 
         r = sd_ipv4acd_set_address(ll->acd, address);
         if (r < 0)

src/network/networkd-ipv4ll.c

@@ -295,9 +295,10 @@ int config_parse_ipv4ll_address(
                            "Failed to parse %s=, ignoring assignment: %s", lvalue, rvalue);
                 return 0;
         }
-        if (!in4_addr_is_link_local(&a.in)) {
+        if (!in4_addr_is_link_local_dynamic(&a.in)) {
                 log_syntax(unit, LOG_WARNING, filename, line, 0,
-                           "Not a IPv4 link local address, ignoring assignment: %s", rvalue);
+                           "Specified address cannot be used as an IPv4 link local address, ignoring assignment: %s",
+                           rvalue);
                 return 0;
         }