networkd: add support to send DHCP user class option (#7499)

This patch add support to enables to send User Class option code 77
RFC 3004.

This option MAY carry multiple User Classes.

The format of this option is as follows:

         Code   Len   Value
        +-----+-----+---------------------  . . .  --+
        | 77  |  N  | User Class Data ('Len' octets) |
        +-----+-----+---------------------  . . .  --+

   where Value consists of one or more instances of User Class Data.
   Each instance of User Class Data is formatted as follows:

         UC_Len_i     User_Class_Data_i
        +--------+------------------------  . . .  --+
        |  L_i   | Opaque-Data ('UC_Len_i' octets)   |
        +--------+------------------------  . . .  --+

UserClass=
A DHCPv4 client can use UserClass option to identify the type or category of user or applications
it represents. The information contained in this option is an string that represents the user class
of which the client is a member. Each class sets an identifying string of information to be used by the DHCP service to classify clients. Takes a whitespace-separated list.

UserClass= hello world how are you

Closes: RFC: #5134

1 files changed, 29 insertions, 0 deletions

diff --git a/src/libsystemd-network/dhcp-option.c b/src/libsystemd-network/dhcp-option.c
index c95597a00b..4832ee6a2c 100644
--- a/src/libsystemd-network/dhcp-option.c
+++ b/src/libsystemd-network/dhcp-option.c
@@ -12,6 +12,7 @@
 
 #include "alloc-util.h"
 #include "utf8.h"
+#include "strv.h"
 
 #include "dhcp-internal.h"
 
@@ -35,6 +36,34 @@ static int option_append(uint8_t options[], size_t size, size_t *offset,
                 *offset += 1;
                 break;
 
+        case SD_DHCP_OPTION_USER_CLASS: {
+                size_t len = 0;
+                char **s;
+
+                STRV_FOREACH(s, (char **) optval)
+                        len += strlen(*s) + 1;
+
+                if (size < *offset + len + 2)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                options[*offset + 1] =  len;
+                *offset += 2;
+
+                STRV_FOREACH(s, (char **) optval) {
+                        len = strlen(*s);
+
+                        if (len > 255)
+                                return -ENAMETOOLONG;
+
+                        options[*offset] = len;
+
+                        memcpy_safe(&options[*offset + 1], *s, len);
+                        *offset += len + 1;
+                }
+
+                break;
+        }
         default:
                 if (size < *offset + optlen + 2)
                         return -ENOBUFS;