systemd: dhcp: move filtering of bogus DNS/NTP addresses out of DHCP client

Imported from systemd:

    The DHCP client should not pre-filter addresses beyond what RFC
    requires. If a client's user (like networkd) wishes to skip/filter
    certain addresses, it's their responsibility.

    The point of this is that the DHCP library does not hide/abstract
    information that might be relevant for certain users. For example,
    NetworkManager exposes DHCP options in its API. When doing that, the
    options should be close to the actual lease.

    This is related to commit d9ec2e632df4905201facf76d6a205edc952116a
    (dhcp4: filter bogus DNS/NTP server addresses silently).

072320eab0

shared/systemd/src/basic/in-addr-util.c

@@ -70,6 +70,14 @@ bool in4_addr_is_localhost(const struct in_addr *a) {
         return (be32toh(a->s_addr) & UINT32_C(0xFF000000)) == UINT32_C(127) << 24;
 }
 
+bool in4_addr_is_non_local(const struct in_addr *a) {
+        /* Whether the address is not null and not localhost.
+         *
+         * As such, it is suitable to configure as DNS/NTP server from DHCP. */
+        return !in4_addr_is_null(a) &&
+               !in4_addr_is_localhost(a);
+}
+
 int in_addr_is_localhost(int family, const union in_addr_union *u) {
         assert(u);
 

shared/systemd/src/basic/in-addr-util.h

@@ -30,6 +30,8 @@ int in_addr_is_link_local(int family, const union in_addr_union *u);
 bool in4_addr_is_localhost(const struct in_addr *a);
 int in_addr_is_localhost(int family, const union in_addr_union *u);
 
+bool in4_addr_is_non_local(const struct in_addr *a);
+
 int in_addr_equal(int family, const union in_addr_union *a, const union in_addr_union *b);
 int in_addr_prefix_intersect(int family, const union in_addr_union *a, unsigned aprefixlen, const union in_addr_union *b, unsigned bprefixlen);
 int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen);

src/systemd/src/libsystemd-network/network-internal.c

@@ -413,16 +413,31 @@ int config_parse_bridge_port_priority(
 }
 #endif /* NM_IGNORED */
 
-void serialize_in_addrs(FILE *f, const struct in_addr *addresses, size_t size) {
+size_t serialize_in_addrs(FILE *f,
-        unsigned i;
+                          const struct in_addr *addresses,
+                          size_t size,
+                          bool with_leading_space,
+                          bool (*predicate)(const struct in_addr *addr)) {
+        size_t count;
+        size_t i;
 
         assert(f);
         assert(addresses);
-        assert(size);
 
-        for (i = 0; i < size; i++)
+        count = 0;
-                fprintf(f, "%s%s", inet_ntoa(addresses[i]),
+
-                        (i < (size - 1)) ? " ": "");
+        for (i = 0; i < size; i++) {
+                if (predicate && !predicate(&addresses[i]))
+                        continue;
+                if (with_leading_space)
+                        fputc(' ', f);
+                else
+                        with_leading_space = true;
+                fputs(inet_ntoa(addresses[i]), f);
+                count++;
+        }
+
+        return count;
 }
 
 int deserialize_in_addrs(struct in_addr **ret, const char *string) {

src/systemd/src/libsystemd-network/network-internal.h

@@ -42,7 +42,11 @@ int net_get_unique_predictable_data(sd_device *device, uint64_t *result);
 const char *net_get_name(sd_device *device);
 #endif /* NM_IGNORED */
 
-void serialize_in_addrs(FILE *f, const struct in_addr *addresses, size_t size);
+size_t serialize_in_addrs(FILE *f,
+                          const struct in_addr *addresses,
+                          size_t size,
+                          bool with_leading_space,
+                          bool (*predicate)(const struct in_addr *addr));
 int deserialize_in_addrs(struct in_addr **addresses, const char *string);
 void serialize_in6_addrs(FILE *f, const struct in6_addr *addresses,
                          size_t size);

src/systemd/src/libsystemd-network/sd-dhcp-lease.c

@@ -372,24 +372,7 @@ static int lease_parse_domain(const uint8_t *option, size_t len, char **ret) {
         return 0;
 }
 
-static void filter_bogus_addresses(struct in_addr *addresses, size_t *n) {
+static int lease_parse_in_addrs(const uint8_t *option, size_t len, struct in_addr **ret, size_t *n_ret) {
-        size_t i, j;
-
-        /* Silently filter DNS/NTP servers supplied to us that do not make outside of the local scope. */
-
-        for (i = 0, j = 0; i < *n; i ++) {
-
-                if (in4_addr_is_null(addresses+i) ||
-                    in4_addr_is_localhost(addresses+i))
-                        continue;
-
-                addresses[j++] = addresses[i];
-        }
-
-        *n = j;
-}
-
-static int lease_parse_in_addrs(const uint8_t *option, size_t len, bool filter_bogus, struct in_addr **ret, size_t *n_ret) {
         assert(option);
         assert(ret);
         assert(n_ret);
@@ -410,9 +393,6 @@ static int lease_parse_in_addrs(const uint8_t *option, size_t len, bool filter_b
                 if (!addresses)
                         return -ENOMEM;
 
-                if (filter_bogus)
-                        filter_bogus_addresses(addresses, &n_addresses);
-
                 free(*ret);
                 *ret = addresses;
                 *n_ret = n_addresses;
@@ -557,19 +537,19 @@ int dhcp_lease_parse_options(uint8_t code, uint8_t len, const void *option, void
                 break;
 
         case SD_DHCP_OPTION_ROUTER:
-                r = lease_parse_in_addrs(option, len, false, &lease->router, &lease->router_size);
+                r = lease_parse_in_addrs(option, len, &lease->router, &lease->router_size);
                 if (r < 0)
                         log_debug_errno(r, "Failed to parse router addresses, ignoring: %m");
                 break;
 
         case SD_DHCP_OPTION_DOMAIN_NAME_SERVER:
-                r = lease_parse_in_addrs(option, len, true, &lease->dns, &lease->dns_size);
+                r = lease_parse_in_addrs(option, len, &lease->dns, &lease->dns_size);
                 if (r < 0)
                         log_debug_errno(r, "Failed to parse DNS server, ignoring: %m");
                 break;
 
         case SD_DHCP_OPTION_NTP_SERVER:
-                r = lease_parse_in_addrs(option, len, true, &lease->ntp, &lease->ntp_size);
+                r = lease_parse_in_addrs(option, len, &lease->ntp, &lease->ntp_size);
                 if (r < 0)
                         log_debug_errno(r, "Failed to parse NTP server, ignoring: %m");
                 break;
@@ -866,7 +846,7 @@ int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file) {
         r = sd_dhcp_lease_get_router(lease, &addresses);
         if (r > 0) {
                 fputs("ROUTER=", f);
-                serialize_in_addrs(f, addresses, r);
+                serialize_in_addrs(f, addresses, r, false, NULL);
                 fputc('\n', f);
         }
 
@@ -901,14 +881,14 @@ int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file) {
         r = sd_dhcp_lease_get_dns(lease, &addresses);
         if (r > 0) {
                 fputs("DNS=", f);
-                serialize_in_addrs(f, addresses, r);
+                serialize_in_addrs(f, addresses, r, false, NULL);
                 fputc('\n', f);
         }
 
         r = sd_dhcp_lease_get_ntp(lease, &addresses);
         if (r > 0) {
                 fputs("NTP=", f);
-                serialize_in_addrs(f, addresses, r);
+                serialize_in_addrs(f, addresses, r, false, NULL);
                 fputc('\n', f);
         }