Merge pull request #15136 from yuwata/network-dhcp4-use-gateway

network: add a flag to ignore gateway provided by DHCP server

man/systemd.network.xml

@@ -1474,7 +1474,13 @@
               "link" scope will be used. For anything else, scope defaults to "global".</para>
           </listitem>
         </varlistentry>
-
+        <varlistentry>
+          <term><varname>UseGateway=</varname></term>
+          <listitem>
+            <para>When true (the default), the gateway will be requested from the DHCP server and added to the
+            routing table with a metric of 1024, and a scope of "link".</para>
+          </listitem>
+        </varlistentry>
         <varlistentry>
           <term><varname>UseTimezone=</varname></term>
 

src/network/networkd-dhcp4.c

@@ -323,6 +323,9 @@ static int link_set_dhcp_routes(Link *link) {
                 }
         }
 
+        if (!link->network->dhcp_use_gateway)
+                return 0;
+
         r = sd_dhcp_lease_get_router(link->dhcp_lease, &router);
         if (IN_SET(r, 0, -ENODATA))
                 log_link_info(link, "DHCP: No gateway received from DHCP server.");
@@ -451,7 +454,7 @@ static int dhcp_remove_router(Link *link, sd_dhcp_lease *lease, const struct in_
         assert(link);
         assert(address);
 
-        if (!link->network->dhcp_use_routes)
+        if (!link->network->dhcp_use_gateway)
                 return 0;
 
         r = sd_dhcp_lease_get_router(lease, &router);

src/network/networkd-network-gperf.gperf

@@ -163,6 +163,7 @@ DHCPv4.UseMTU,                               config_parse_bool,
 DHCPv4.UseHostname,                          config_parse_bool,                                        0,                             offsetof(Network, dhcp_use_hostname)
 DHCPv4.UseDomains,                           config_parse_dhcp_use_domains,                            0,                             offsetof(Network, dhcp_use_domains)
 DHCPv4.UseRoutes,                            config_parse_bool,                                        0,                             offsetof(Network, dhcp_use_routes)
+DHCPv4.UseGateway,                           config_parse_bool,                                        0,                             offsetof(Network, dhcp_use_gateway)
 DHCPv4.RequestOptions,                       config_parse_dhcp_request_options,                        0,                             0
 DHCPv4.Anonymize,                            config_parse_bool,                                        0,                             offsetof(Network, dhcp_anonymize)
 DHCPv4.SendHostname,                         config_parse_bool,                                        0,                             offsetof(Network, dhcp_send_hostname)

src/network/networkd-network.c

@@ -384,6 +384,7 @@ int network_load_one(Manager *manager, OrderedHashmap **networks, const char *fi
                 .dhcp_use_dns = true,
                 .dhcp_use_hostname = true,
                 .dhcp_use_routes = true,
+                .dhcp_use_gateway = true,
                 /* NOTE: this var might be overwritten by network_apply_anonymize_if_set */
                 .dhcp_send_hostname = true,
                 .dhcp_send_release = true,

src/network/networkd-network.h

@@ -109,6 +109,7 @@ struct Network {
         bool dhcp_use_sip;
         bool dhcp_use_mtu;
         bool dhcp_use_routes;
+        bool dhcp_use_gateway;
         bool dhcp_use_timezone;
         bool rapid_commit;
         bool dhcp_use_hostname;

test/fuzz/fuzz-network-parser/directives.network

@@ -73,6 +73,7 @@ UseDNS=
 RoutesToDNS=
 UseDomains=
 UseRoutes=
+UseGateway=
 IAID=
 UserClass=
 UseNTP=

test/test-network/conf/dhcp-client-ipv4-use-gateway-no.network

@@ -0,0 +1,9 @@
+[Match]
+Name=veth99
+
+[Network]
+DHCP=ipv4
+IPv6AcceptRA=false
+
+[DHCPv4]
+UseGateway=no

test/test-network/systemd-networkd-tests.py

@@ -2921,6 +2921,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         'dhcp-client-ipv4-dhcp-settings.network',
         'dhcp-client-ipv4-only-ipv6-disabled.network',
         'dhcp-client-ipv4-only.network',
+        'dhcp-client-ipv4-use-gateway-no.network',
         'dhcp-client-ipv4-use-routes-no.network',
         'dhcp-client-ipv6-only.network',
         'dhcp-client-ipv6-rapid-commit.network',
@@ -3040,6 +3041,19 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         self.assertRegex(output, r'default via 192.168.5.1 proto dhcp src 192.168.5.181 metric 1024')
         self.assertRegex(output, r'192.168.5.1 proto dhcp scope link src 192.168.5.181 metric 1024')
 
+    def test_dhcp_client_ipv4_use_gateway_no(self):
+        copy_unit_to_networkd_unit_path('25-veth.netdev', 'dhcp-server-veth-peer.network', 'dhcp-client-ipv4-use-gateway-no.network')
+
+        start_networkd()
+        self.wait_online(['veth-peer:carrier'])
+        start_dnsmasq(additional_options='--dhcp-option=option:dns-server,192.168.5.6,192.168.5.7', lease_time='2m')
+        self.wait_online(['veth99:routable', 'veth-peer:routable'])
+
+        output = check_output('ip route show dev veth99')
+        print(output)
+        self.assertRegex(output, r'192.168.5.0/24 via 192.168.5.5 proto dhcp src 192.168.5.181 metric 1024')
+        self.assertNotRegex(output, r'default via 192.168.5.1')
+
     def test_dhcp_client_ipv4_ipv6(self):
         copy_unit_to_networkd_unit_path('25-veth.netdev', 'dhcp-server-veth-peer.network', 'dhcp-client-ipv6-only.network',
                                         'dhcp-client-ipv4-only.network')