ether-addr-util: introduce hw_addr_is_valid()

Take this from udev, and adapt it to make it re-usable elsewhere.

src/basic/ether-addr-util.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include <net/ethernet.h>
+#include <net/if_arp.h>
 #include <stdio.h>
 
 #include "ether-addr-util.h"
@@ -68,6 +69,29 @@ bool hw_addr_is_null(const struct hw_addr_data *addr) {
         return addr->length == 0 || memeqzero(addr->bytes, addr->length);
 }
 
+bool hw_addr_is_valid(const struct hw_addr_data *addr, uint16_t iftype) {
+        assert(addr);
+
+        switch (iftype) {
+        case ARPHRD_ETHER:
+                /* Refuse all zero and all 0xFF. */
+                if (addr->length != ETH_ALEN)
+                        return false;
+
+                return !ether_addr_is_null(&addr->ether) && !ether_addr_is_broadcast(&addr->ether);
+
+        case ARPHRD_INFINIBAND:
+                /* The last 8 bytes cannot be zero. */
+                if (addr->length != INFINIBAND_ALEN)
+                        return false;
+
+                return !memeqzero(addr->bytes + INFINIBAND_ALEN - 8, 8);
+
+        default:
+                return false;
+        }
+}
+
 DEFINE_HASH_OPS(hw_addr_hash_ops, struct hw_addr_data, hw_addr_hash_func, hw_addr_compare);
 DEFINE_HASH_OPS_WITH_KEY_DESTRUCTOR(hw_addr_hash_ops_free, struct hw_addr_data, hw_addr_hash_func, hw_addr_compare, free);
 

src/basic/ether-addr-util.h

@@ -57,6 +57,7 @@ static inline bool hw_addr_equal(const struct hw_addr_data *a, const struct hw_a
         return hw_addr_compare(a, b) == 0;
 }
 bool hw_addr_is_null(const struct hw_addr_data *addr) _pure_;
+bool hw_addr_is_valid(const struct hw_addr_data *addr, uint16_t iftype);
 
 extern const struct hash_ops hw_addr_hash_ops;
 extern const struct hash_ops hw_addr_hash_ops_free;

src/udev/net/link-config.c

@@ -558,26 +558,6 @@ static int link_apply_ethtool_settings(Link *link, int *ethtool_fd) {
         return 0;
 }
 
-static bool hw_addr_is_valid(Link *link, const struct hw_addr_data *hw_addr) {
-        assert(link);
-        assert(hw_addr);
-
-        switch (link->iftype) {
-        case ARPHRD_ETHER:
-                /* Refuse all zero and all 0xFF. */
-                assert(hw_addr->length == ETH_ALEN);
-                return !ether_addr_is_null(&hw_addr->ether) && !ether_addr_is_broadcast(&hw_addr->ether);
-
-        case ARPHRD_INFINIBAND:
-                /* The last 8 bytes cannot be zero. */
-                assert(hw_addr->length == INFINIBAND_ALEN);
-                return !memeqzero(hw_addr->bytes + INFINIBAND_ALEN - 8, 8);
-
-        default:
-                assert_not_reached();
-        }
-}
-
 static int link_generate_new_hw_addr(Link *link, struct hw_addr_data *ret) {
         struct hw_addr_data hw_addr = HW_ADDR_NULL;
         bool is_static = false;
@@ -647,7 +627,7 @@ static int link_generate_new_hw_addr(Link *link, struct hw_addr_data *ret) {
                  * systems booting up at the very same time. */
                 for (;;) {
                         random_bytes(p, len);
-                        if (hw_addr_is_valid(link, &hw_addr))
+                        if (hw_addr_is_valid(&hw_addr, link->iftype))
                                 break;
                 }
 
@@ -662,7 +642,7 @@ static int link_generate_new_hw_addr(Link *link, struct hw_addr_data *ret) {
 
                 assert(len <= sizeof(result));
                 memcpy(p, &result, len);
-                if (!hw_addr_is_valid(link, &hw_addr))
+                if (!hw_addr_is_valid(&hw_addr, link->iftype))
                         return log_link_warning_errno(link, SYNTHETIC_ERRNO(EINVAL),
                                                       "Could not generate valid persistent MAC address.");
         }