networkd: dhcp server Support Vendor specific 43

Implementes https://tools.ietf.org/html/rfc2132

```
[DHCPServer]
SendRawOption=26:uint32:1400
SendRawOption=23:uint8:10

```
Frame 448: 350 bytes on wire (2800 bits), 350 bytes captured (2800 bits) on interface 0
Linux cooked capture
Internet Protocol Version 4, Src: 192.168.5.1, Dst: 192.168.5.11
User Datagram Protocol, Src Port: 67, Dst Port: 68
Dynamic Host Configuration Protocol (ACK)
    Message type: Boot Reply (2)
    Hardware type: Ethernet (0x01)
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x71f8de9d
    Seconds elapsed: 0
    Bootp flags: 0x0000 (Unicast)
    Client IP address: 0.0.0.0
    Your (client) IP address: 192.168.5.11
    Next server IP address: 0.0.0.0
    Relay agent IP address: 0.0.0.0
    Client MAC address: 1e:04:f8:b8:2f:d4 (1e:04:f8:b8:2f:d4)
    Client hardware address padding: 00000000000000000000
    Server host name not given
    Boot file name not given
    Magic cookie: DHCP
    Option: (53) DHCP Message Type (ACK)
        Length: 1
        DHCP: ACK (5)
    Option: (51) IP Address Lease Time
        Length: 4
        IP Address Lease Time: (3600s) 1 hour
    Option: (1) Subnet Mask (255.255.255.0)
        Length: 4
        Subnet Mask: 255.255.255.0
    Option: (3) Router
        Length: 4
        Router: 192.168.5.1
    Option: (6) Domain Name Server
        Length: 4
        Domain Name Server: 192.168.5.1
    Option: (42) Network Time Protocol Servers
        Length: 4
        Network Time Protocol Server: 192.168.5.1
    Option: (101) TCode
        Length: 13
        TZ TCode: Europe/Berlin
    Option: (43) Vendor-Specific Information
        Length: 9
        Value: 1701311a0431343030
    Option: (54) DHCP Server Identifier (192.168.5.1)
        Length: 4
        DHCP Server Identifier: 192.168.5.1
    Option: (255) End
        Option End: 255

```

3 files changed, 119 insertions, 1 deletions

diff --git a/src/libsystemd-network/dhcp-option.c b/src/libsystemd-network/dhcp-option.c
index d2f1f5d806..78baeb7333 100644
--- a/src/libsystemd-network/dhcp-option.c
+++ b/src/libsystemd-network/dhcp-option.c
@@ -10,6 +10,7 @@
 
 #include "alloc-util.h"
 #include "dhcp-internal.h"
+#include "dhcp-server-internal.h"
 #include "memory-util.h"
 #include "strv.h"
 #include "utf8.h"
@@ -77,6 +78,32 @@ static int option_append(uint8_t options[], size_t size, size_t *offset,
                 *offset += 3 + optlen;
 
                 break;
+        case SD_DHCP_OPTION_VENDOR_SPECIFIC: {
+                OrderedHashmap *s = (OrderedHashmap *) optval;
+                struct sd_dhcp_raw_option *p;
+                size_t l = 0;
+                Iterator i;
+
+                ORDERED_HASHMAP_FOREACH(p, s, i)
+                        l += p->length + 2;
+
+                if (*offset + l + 2 > size)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                options[*offset + 1] = l;
+
+                *offset += 2;
+
+                ORDERED_HASHMAP_FOREACH(p, s, i) {
+                        options[*offset] = p->type;
+                        options[*offset + 1] = p->length;
+                        memcpy(&options[*offset + 2], p->data, p->length);
+                        *offset += 2 + p->length;
+                }
+
+                break;
+        }
         default:
                 if (*offset + 2 + optlen > size)
                         return -ENOBUFS;
diff --git a/src/libsystemd-network/dhcp-server-internal.h b/src/libsystemd-network/dhcp-server-internal.h
index 0a64082cd1..e537d9e622 100644
--- a/src/libsystemd-network/dhcp-server-internal.h
+++ b/src/libsystemd-network/dhcp-server-internal.h
@@ -13,6 +13,16 @@
 #include "log.h"
 #include "time-util.h"
 
+typedef enum DHCPRawOption {
+        DHCP_RAW_OPTION_DATA_UINT8,
+        DHCP_RAW_OPTION_DATA_UINT16,
+        DHCP_RAW_OPTION_DATA_UINT32,
+        DHCP_RAW_OPTION_DATA_STRING,
+        DHCP_RAW_OPTION_DATA_IPV4ADDRESS,
+        _DHCP_RAW_OPTION_DATA_MAX,
+        _DHCP_RAW_OPTION_DATA_INVALID,
+} DHCPRawOption;
+
 typedef struct DHCPClientId {
         size_t length;
         void *data;
@@ -27,6 +37,15 @@ typedef struct DHCPLease {
         usec_t expiration;
 } DHCPLease;
 
+struct sd_dhcp_raw_option {
+        unsigned n_ref;
+
+        uint8_t type;
+        uint8_t length;
+
+        void *data;
+};
+
 struct sd_dhcp_server {
         unsigned n_ref;
 
@@ -48,6 +67,8 @@ struct sd_dhcp_server {
         struct in_addr *ntp, *dns, *sip;
         unsigned n_ntp, n_dns, n_sip;
 
+        OrderedHashmap *raw_option;
+
         bool emit_router;
 
         Hashmap *leases_by_client_id;
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index bba82c21dd..9e1a7698fc 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -127,6 +127,46 @@ int client_id_compare_func(const DHCPClientId *a, const DHCPClientId *b) {
 DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR(dhcp_lease_hash_ops, DHCPClientId, client_id_hash_func, client_id_compare_func,
                                               DHCPLease, dhcp_lease_free);
 
+static sd_dhcp_raw_option* raw_option_free(sd_dhcp_raw_option *i) {
+        if (!i)
+                return NULL;
+
+        free(i->data);
+        return mfree(i);
+}
+
+_public_ int sd_dhcp_raw_option_new(uint8_t type, char *data, size_t length, sd_dhcp_raw_option **ret) {
+        sd_dhcp_raw_option *p;
+
+        assert_return(ret, -EINVAL);
+
+        p = new(sd_dhcp_raw_option, 1);
+        if (!p)
+                return -ENOMEM;
+
+        *p = (sd_dhcp_raw_option) {
+                  .n_ref = 1,
+                  .data = memdup(data, length),
+                  .length = length,
+                  .type = type,
+        };
+
+        if (!p->data)
+                return -ENOMEM;
+
+        *ret = p;
+        return 0;
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_raw_option, sd_dhcp_raw_option, raw_option_free);
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+                dhcp_raw_options_hash_ops,
+                void,
+                trivial_hash_func,
+                trivial_compare_func,
+                sd_dhcp_raw_option,
+                sd_dhcp_raw_option_unref);
+
 static sd_dhcp_server *dhcp_server_free(sd_dhcp_server *server) {
         assert(server);
 
@@ -143,6 +183,8 @@ static sd_dhcp_server *dhcp_server_free(sd_dhcp_server *server) {
 
         hashmap_free(server->leases_by_client_id);
 
+        ordered_hashmap_free(server->raw_option);
+
         free(server->bound_leases);
         return mfree(server);
 }
@@ -452,8 +494,8 @@ static int server_send_offer(sd_dhcp_server *server, DHCPRequest *req,
 static int server_send_ack(sd_dhcp_server *server, DHCPRequest *req,
                            be32_t address) {
         _cleanup_free_ DHCPPacket *packet = NULL;
-        size_t offset;
         be32_t lease_time;
+        size_t offset;
         int r;
 
         r = server_message_init(server, &packet, DHCP_ACK, &offset, req);
@@ -517,6 +559,15 @@ static int server_send_ack(sd_dhcp_server *server, DHCPRequest *req,
                         return r;
         }
 
+        if (!ordered_hashmap_isempty(server->raw_option)) {
+                r = dhcp_option_append(
+                                &packet->dhcp, req->max_optlen, &offset, 0,
+                                SD_DHCP_OPTION_VENDOR_SPECIFIC,
+                                ordered_hashmap_size(server->raw_option), server->raw_option);
+                if (r < 0)
+                        return r;
+        }
+
         r = dhcp_server_send_packet(server, req, packet, DHCP_ACK, offset);
         if (r < 0)
                 return r;
@@ -1170,3 +1221,22 @@ int sd_dhcp_server_set_emit_router(sd_dhcp_server *server, int enabled) {
 
         return 1;
 }
+
+int sd_dhcp_server_add_raw_option(sd_dhcp_server *server, sd_dhcp_raw_option *v) {
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(v, -EINVAL);
+
+        r = ordered_hashmap_ensure_allocated(&server->raw_option, &dhcp_raw_options_hash_ops);
+        if (r < 0)
+                return -ENOMEM;
+
+        r = ordered_hashmap_put(server->raw_option, v, v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp_raw_option_ref(v);
+
+        return 1;
+}