dhcp4: make IPServiceType configurable

IPServiceType set to CS6 (network control) causes problems on some old
network setups that continue to interpret the field as IP TOS.

Make DHCP work on such networks by allowing this field to be set to
CS4 (Realtime) instead, as this maps to IPTOS_LOWDELAY.

Signed-off-by: Siddharth Chandrasekaran <csiddharth@vmware.com>

15 files changed, 79 insertions, 13 deletions

diff --git a/man/systemd.network.xml b/man/systemd.network.xml
index 585041095d..e5f9d6f470 100644
--- a/man/systemd.network.xml
+++ b/man/systemd.network.xml
@@ -1309,7 +1309,14 @@
           <para>Note that if IPv6 is enabled on the interface, and the MTU is chosen
           below 1280 (the minimum MTU for IPv6) it will automatically be increased to this value.</para>
         </listitem>
-      </varlistentry>
+        </varlistentry>
+        <varlistentry>
+          <term><varname>IPServiceType=</varname></term>
+          <listitem>
+            <para>Takes string; "CS6" or "CS4". Used to set IP service type to CS6 (network control)
+            or CS4 (Realtime). IPServiceType defaults to CS6 if nothing is specified.</para>
+          </listitem>
+        </varlistentry>
       </variablelist>
   </refsect1>
 
diff --git a/src/libsystemd-network/dhcp-internal.h b/src/libsystemd-network/dhcp-internal.h
index e0269b5456..c231773bdd 100644
--- a/src/libsystemd-network/dhcp-internal.h
+++ b/src/libsystemd-network/dhcp-internal.h
@@ -19,7 +19,7 @@ int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
                                  uint32_t xid, const uint8_t *mac_addr,
                                  size_t mac_addr_len, uint16_t arp_type,
                                  uint16_t port);
-int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port);
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type);
 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
                                  const void *packet, size_t len);
 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
@@ -41,7 +41,7 @@ uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len);
 
 void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
                                    uint16_t source, be32_t destination_addr,
-                                   uint16_t destination, uint16_t len);
+                                   uint16_t destination, uint16_t len, int ip_service_type);
 
 int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port);
 
diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
index 94c10ed14c..8e7f8a65ab 100644
--- a/src/libsystemd-network/dhcp-network.c
+++ b/src/libsystemd-network/dhcp-network.c
@@ -146,7 +146,7 @@ int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
                                 bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 }
 
-int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
         union sockaddr_union src = {
                 .in.sin_family = AF_INET,
                 .in.sin_port = htobe16(port),
@@ -159,7 +159,11 @@ int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
         if (s < 0)
                 return -errno;
 
-        r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
+        if (ip_service_type >= 0)
+                r = setsockopt_int(s, IPPROTO_IP, IP_TOS, ip_service_type);
+        else
+                r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
+
         if (r < 0)
                 return r;
 
diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c
index ad5f8e267a..fe7d51703b 100644
--- a/src/libsystemd-network/dhcp-packet.c
+++ b/src/libsystemd-network/dhcp-packet.c
@@ -75,12 +75,15 @@ uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) {
 
 void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
                                    uint16_t source_port, be32_t destination_addr,
-                                   uint16_t destination_port, uint16_t len) {
+                                   uint16_t destination_port, uint16_t len, int ip_service_type) {
         packet->ip.version = IPVERSION;
         packet->ip.ihl = DHCP_IP_SIZE / 4;
         packet->ip.tot_len = htobe16(len);
 
-        packet->ip.tos = IPTOS_CLASS_CS6;
+        if (ip_service_type >= 0)
+                packet->ip.tos = ip_service_type;
+        else
+                packet->ip.tos = IPTOS_CLASS_CS6;
 
         packet->ip.protocol = IPPROTO_UDP;
         packet->ip.saddr = source_addr;
diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index cadacc24d4..2d511f7feb 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -98,6 +98,7 @@ struct sd_dhcp_client {
         void *userdata;
         sd_dhcp_lease *lease;
         usec_t start_delay;
+        int ip_service_type;
 };
 
 static const uint8_t default_req_opts[] = {
@@ -541,6 +542,14 @@ int sd_dhcp_client_get_lease(sd_dhcp_client *client, sd_dhcp_lease **ret) {
         return 0;
 }
 
+int sd_dhcp_client_set_service_type(sd_dhcp_client *client, int type) {
+        assert_return(client, -EINVAL);
+
+        client->ip_service_type = type;
+
+        return 0;
+}
+
 static int client_notify(sd_dhcp_client *client, int event) {
         assert(client);
 
@@ -773,7 +782,7 @@ static int dhcp_client_send_raw(
                 size_t len) {
 
         dhcp_packet_append_ip_headers(packet, INADDR_ANY, client->port,
-                                      INADDR_BROADCAST, DHCP_PORT_SERVER, len);
+                                      INADDR_BROADCAST, DHCP_PORT_SERVER, len, client->ip_service_type);
 
         return dhcp_network_send_raw_socket(client->fd, &client->link,
                                             packet, len);
@@ -1661,7 +1670,7 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message, i
                                 goto error;
                         }
 
-                        r = dhcp_network_bind_udp_socket(client->ifindex, client->lease->address, client->port);
+                        r = dhcp_network_bind_udp_socket(client->ifindex, client->lease->address, client->port, client->ip_service_type);
                         if (r < 0) {
                                 log_dhcp_client(client, "could not bind UDP socket");
                                 goto error;
@@ -2013,6 +2022,7 @@ int sd_dhcp_client_new(sd_dhcp_client **ret, int anonymize) {
                 .port = DHCP_PORT_CLIENT,
                 .anonymize = !!anonymize,
                 .max_attempts = (uint64_t) -1,
+                .ip_service_type = -1,
         };
         /* NOTE: this could be moved to a function. */
         if (anonymize) {
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 13f104f9ef..bba82c21dd 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -244,7 +244,7 @@ static int dhcp_server_send_unicast_raw(sd_dhcp_server *server,
 
         dhcp_packet_append_ip_headers(packet, server->address, DHCP_PORT_SERVER,
                                       packet->dhcp.yiaddr,
-                                      DHCP_PORT_CLIENT, len);
+                                      DHCP_PORT_CLIENT, len, -1);
 
         return dhcp_network_send_raw_socket(server->fd_raw, &link, packet, len);
 }
@@ -994,7 +994,7 @@ int sd_dhcp_server_start(sd_dhcp_server *server) {
         }
         server->fd_raw = r;
 
-        r = dhcp_network_bind_udp_socket(server->ifindex, INADDR_ANY, DHCP_PORT_SERVER);
+        r = dhcp_network_bind_udp_socket(server->ifindex, INADDR_ANY, DHCP_PORT_SERVER, -1);
         if (r < 0) {
                 sd_dhcp_server_stop(server);
                 return r;
diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
index 5f31d24d20..4e9b388a45 100644
--- a/src/libsystemd-network/test-dhcp-client.c
+++ b/src/libsystemd-network/test-dhcp-client.c
@@ -269,7 +269,7 @@ int dhcp_network_bind_raw_socket(
         return test_fd[0];
 }
 
-int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
         int fd;
 
         fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
diff --git a/src/network/networkd-conf.c b/src/network/networkd-conf.c
index 1ef5beb203..eef7788c49 100644
--- a/src/network/networkd-conf.c
+++ b/src/network/networkd-conf.c
@@ -4,6 +4,7 @@
  ***/
 
 #include <ctype.h>
+#include <netinet/ip.h>
 
 #include "conf-parser.h"
 #include "def.h"
@@ -14,6 +15,7 @@
 #include "networkd-manager.h"
 #include "networkd-network.h"
 #include "networkd-speed-meter.h"
+#include "networkd-dhcp4.h"
 #include "string-table.h"
 
 int manager_parse_config_file(Manager *m) {
@@ -180,3 +182,30 @@ int config_parse_duid_rawdata(
         ret->raw_data_len = count;
         return 0;
 }
+
+int config_parse_ip_service_type(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+
+        if (streq(rvalue, "CS4"))
+                *((int *)data) = IPTOS_CLASS_CS4;
+        else if (streq(rvalue, "CS6"))
+                *((int *)data) = IPTOS_CLASS_CS6;
+        else
+                log_syntax(unit, LOG_WARNING, filename, line, 0,
+                           "Failed to parse IPServiceType type '%s', ignoring.", rvalue);
+
+        return 0;
+}
diff --git a/src/network/networkd-conf.h b/src/network/networkd-conf.h
index 88a2c64031..a615998f92 100644
--- a/src/network/networkd-conf.h
+++ b/src/network/networkd-conf.h
@@ -15,3 +15,4 @@ const struct ConfigPerfItem* networkd_gperf_lookup(const char *key, GPERF_LEN_TY
 
 CONFIG_PARSER_PROTOTYPE(config_parse_duid_type);
 CONFIG_PARSER_PROTOTYPE(config_parse_duid_rawdata);
+CONFIG_PARSER_PROTOTYPE(config_parse_ip_service_type);
diff --git a/src/network/networkd-dhcp4.c b/src/network/networkd-dhcp4.c
index 06e87199c6..78cd241140 100644
--- a/src/network/networkd-dhcp4.c
+++ b/src/network/networkd-dhcp4.c
@@ -1213,7 +1213,12 @@ int dhcp4_configure(Link *link) {
                         return log_link_error_errno(link, r, "DHCP4 CLIENT: Failed to set max attempts: %m");
         }
 
-        return dhcp4_set_client_identifier(link);
+        if (link->network->ip_service_type > 0) {
+                r = sd_dhcp_client_set_service_type(link->dhcp_client, link->network->ip_service_type);
+                if (r < 0)
+                        return log_link_error_errno(link, r, "DHCP4 CLIENT: Failed to set ip service type: %m");
+        }
+       return dhcp4_set_client_identifier(link);
 }
 
 int config_parse_dhcp_max_attempts(
diff --git a/src/network/networkd-network-gperf.gperf b/src/network/networkd-network-gperf.gperf
index 11e541e093..ce9fc30162 100644
--- a/src/network/networkd-network-gperf.gperf
+++ b/src/network/networkd-network-gperf.gperf
@@ -167,6 +167,7 @@ DHCPv4.IAID,                            config_parse_iaid,
 DHCPv4.ListenPort,                      config_parse_uint16,                             0,                             offsetof(Network, dhcp_client_port)
 DHCPv4.SendRelease,                     config_parse_bool,                               0,                             offsetof(Network, dhcp_send_release)
 DHCPv4.BlackList,                       config_parse_dhcp_black_listed_ip_address,       0,                             0
+DHCPv4.IPServiceType,                   config_parse_ip_service_type,                    0,                             offsetof(Network, ip_service_type)
 DHCPv6.UseDNS,                          config_parse_bool,                               0,                             offsetof(Network, dhcp6_use_dns)
 DHCPv6.UseNTP,                          config_parse_bool,                               0,                             offsetof(Network, dhcp6_use_ntp)
 DHCPv6.RapidCommit,                     config_parse_bool,                               0,                             offsetof(Network, rapid_commit)
diff --git a/src/network/networkd-network.c b/src/network/networkd-network.c
index a2cd7f4c60..23a21d8c9e 100644
--- a/src/network/networkd-network.c
+++ b/src/network/networkd-network.c
@@ -442,6 +442,7 @@ int network_load_one(Manager *manager, const char *filename) {
                 .keep_configuration = _KEEP_CONFIGURATION_INVALID,
 
                 .can_triple_sampling = -1,
+                .ip_service_type = -1,
         };
 
         r = config_parse_many(filename, NETWORK_DIRS, dropin_dirname,
diff --git a/src/network/networkd-network.h b/src/network/networkd-network.h
index 837206a29c..ff97845dd1 100644
--- a/src/network/networkd-network.h
+++ b/src/network/networkd-network.h
@@ -104,6 +104,7 @@ struct Network {
         DHCPUseDomains dhcp_use_domains;
         Set *dhcp_black_listed_ip;
         Set *dhcp_request_options;
+        int ip_service_type;
 
         /* DHCPv6 Client support*/
         bool dhcp6_use_dns;
diff --git a/src/systemd/sd-dhcp-client.h b/src/systemd/sd-dhcp-client.h
index d2d74b2b4c..98e3281397 100644
--- a/src/systemd/sd-dhcp-client.h
+++ b/src/systemd/sd-dhcp-client.h
@@ -174,6 +174,9 @@ int sd_dhcp_client_set_user_class(
 int sd_dhcp_client_get_lease(
                 sd_dhcp_client *client,
                 sd_dhcp_lease **ret);
+int sd_dhcp_client_set_service_type(
+                sd_dhcp_client *client,
+                int type);
 
 int sd_dhcp_client_stop(sd_dhcp_client *client);
 int sd_dhcp_client_start(sd_dhcp_client *client);
diff --git a/test/fuzz/fuzz-network-parser/directives.network b/test/fuzz/fuzz-network-parser/directives.network
index 3be643075a..78cddcab77 100644
--- a/test/fuzz/fuzz-network-parser/directives.network
+++ b/test/fuzz/fuzz-network-parser/directives.network
@@ -93,6 +93,7 @@ BlackList=
 RequestOptions=
 SendRelease=
 MaxAttempts=
+IPServiceType=
 [DHCPv6]
 UseNTP=
 UseDNS=