sd-network: DHCPv6 - Add support to send vendor class data

```
21.16.  Vendor Class Option

   This option is used by a client to identify the vendor that
   manufactured the hardware on which the client is running.  The
   information contained in the data area of this option is contained in
   one or more opaque fields that identify details of the hardware
   configuration.  The format of the Vendor Class option is:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      OPTION_VENDOR_CLASS      |           option-len          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       enterprise-number                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                       vendor-class-data                       .
      .                             . . .                             .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 28: Vendor Class Option Format

      option-code          OPTION_VENDOR_CLASS (16).

      option-len           4 + length of vendor-class-data field.

      enterprise-number    The vendor's registered Enterprise Number as
                           maintained by IANA [IANA-PEN].  A 4-octet
                           field containing an unsigned integer.

      vendor-class-data    The hardware configuration of the node on
                           which the client is running.  A
                           variable-length field (4 octets less than the
                           value in the option-len field).

   The vendor-class-data field is composed of a series of separate
   items, each of which describes some characteristic of the client's
   hardware configuration.  Examples of vendor-class-data instances
   might include the version of the operating system the client is
   running or the amount of memory installed on the client.

   Each instance of vendor-class-data is formatted as follows:

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
      |       vendor-class-len        |          opaque-data          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+

               Figure 29: Format of vendor-class-data Field

   The vendor-class-len field is 2 octets long and specifies the length
   of the opaque vendor-class-data in network byte order.

   Servers and clients MUST NOT include more than one instance of
   OPTION_VENDOR_CLASS with the same Enterprise Number.  Each instance
   of OPTION_VENDOR_CLASS can carry multiple vendor-class-data
   instances.
   ```

1 files changed, 43 insertions, 1 deletions

diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
index 0240f1b7c7..ce9e6cae7e 100644
--- a/src/libsystemd-network/sd-dhcp6-client.c
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -68,6 +68,7 @@ struct sd_dhcp6_client {
         char *fqdn;
         char *mudurl;
         char **user_class;
+        char **vendor_class;
         sd_event_source *receive_message;
         usec_t retransmit_time;
         uint8_t retransmit_count;
@@ -380,7 +381,7 @@ int sd_dhcp6_client_set_request_mud_url(sd_dhcp6_client *client, const char *mud
         assert_return(client, -EINVAL);
         assert_return(client->state == DHCP6_STATE_STOPPED, -EBUSY);
         assert_return(mudurl, -EINVAL);
-        assert_return(strlen(mudurl) <= 255, -EINVAL);
+        assert_return(strlen(mudurl) <= UINT8_MAX, -EINVAL);
         assert_return(http_url_is_valid(mudurl), -EINVAL);
 
         return free_and_strdup(&client->mudurl, mudurl);
@@ -392,6 +393,7 @@ int sd_dhcp6_client_set_request_user_class(sd_dhcp6_client *client, char **user_
 
         assert_return(client, -EINVAL);
         assert_return(client->state == DHCP6_STATE_STOPPED, -EBUSY);
+
         assert_return(user_class, -EINVAL);
 
         STRV_FOREACH(p, user_class)
@@ -407,6 +409,27 @@ int sd_dhcp6_client_set_request_user_class(sd_dhcp6_client *client, char **user_
         return 0;
 }
 
+int sd_dhcp6_client_set_request_vendor_class(sd_dhcp6_client *client, char **vendor_class) {
+        _cleanup_strv_free_ char **s = NULL;
+        char **p;
+
+        assert_return(client, -EINVAL);
+        assert_return(client->state == DHCP6_STATE_STOPPED, -EBUSY);
+        assert_return(vendor_class, -EINVAL);
+
+        STRV_FOREACH(p, vendor_class)
+                if (strlen(*p) > UINT8_MAX)
+                        return -ENAMETOOLONG;
+
+        s = strv_copy(vendor_class);
+        if (!s)
+                return -ENOMEM;
+
+        client->vendor_class = TAKE_PTR(s);
+
+        return 0;
+}
+
 int sd_dhcp6_client_get_prefix_delegation(sd_dhcp6_client *client, int *delegation) {
         assert_return(client, -EINVAL);
         assert_return(delegation, -EINVAL);
@@ -593,6 +616,12 @@ static int client_send_message(sd_dhcp6_client *client, usec_t time_now) {
                                 return r;
                 }
 
+                if (client->vendor_class) {
+                        r = dhcp6_option_append_vendor_class(&opt, &optlen, client->vendor_class);
+                        if (r < 0)
+                                return r;
+                }
+
                 if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD)) {
                         r = dhcp6_option_append_pd(opt, optlen, &client->ia_pd, &client->hint_pd_prefix);
                         if (r < 0)
@@ -645,6 +674,12 @@ static int client_send_message(sd_dhcp6_client *client, usec_t time_now) {
                                 return r;
                 }
 
+                if (client->vendor_class) {
+                        r = dhcp6_option_append_vendor_class(&opt, &optlen, client->vendor_class);
+                        if (r < 0)
+                                return r;
+                }
+
                 if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD)) {
                         r = dhcp6_option_append_pd(opt, optlen, &client->lease->pd, NULL);
                         if (r < 0)
@@ -685,6 +720,12 @@ static int client_send_message(sd_dhcp6_client *client, usec_t time_now) {
                                 return r;
                 }
 
+                if (client->vendor_class) {
+                        r = dhcp6_option_append_vendor_class(&opt, &optlen, client->vendor_class);
+                        if (r < 0)
+                                return r;
+                }
+
                 if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD)) {
                         r = dhcp6_option_append_pd(opt, optlen, &client->lease->pd, NULL);
                         if (r < 0)
@@ -1645,6 +1686,7 @@ static sd_dhcp6_client *dhcp6_client_free(sd_dhcp6_client *client) {
 
         ordered_hashmap_free(client->extra_options);
         strv_free(client->user_class);
+        strv_free(client->vendor_class);
 
         return mfree(client);
 }