udhcpc6: fix udhcp_find_option to actually find DHCP6 options

udhcp_insert_new_option treats code for IPv6 as follows:

new->data[D6_OPT_CODE] = code >> 8;
new->data[D6_OPT_CODE + 1] = code & 0xff;

udhcp_find_option tests the code as follows:

while (opt_list && opt_list->data[OPT_CODE] < code)
...
if (opt_list && opt_list->data[OPT_CODE] == code)

So yes, OPT_CODE and D6_OPT_CODE are both 0, but the D6_OPT_CLIENTID =
1 value means that the 1 is in the seconds byte, and udhcp_find_option
is only looking at the first byte,  So the send_d6_release can never
find it the created option.

function                                             old     new   delta
udhcp_find_option                                     28      53     +25
attach_option                                        276     284      +8
udhcpc6_main                                        2602    2607      +5
perform_d6_release                                   262     267      +5
udhcpd_main                                         1518    1520      +2
udhcpc_main                                         2542    2544      +2
add_serverid_and_clientid_options                     46      48      +2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 7/0 up/down: 49/0)               Total: 49 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 331f13a8c..c757fb37c 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -658,7 +658,7 @@ static void add_client_options(struct dhcp_packet *packet)
 
         // This will be needed if we remove -V VENDOR_STR in favor of
         // -x vendor:VENDOR_STR
-        //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
+        //if (!udhcp_find_option(packet.options, DHCP_VENDOR, /*dhcpv6:*/ 0))
         //      /* not set, set the default vendor ID */
         //      ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
 }
@@ -676,7 +676,7 @@ static void add_serverid_and_clientid_options(struct dhcp_packet *packet, uint32
          * If the client used a 'client identifier' when it obtained the lease,
          * it MUST use the same 'client identifier' in the DHCPRELEASE message.
          */
-        ci = udhcp_find_option(client_data.options, DHCP_CLIENT_ID);
+        ci = udhcp_find_option(client_data.options, DHCP_CLIENT_ID, /*dhcpv6:*/ 0);
         if (ci)
                 udhcp_add_binary_option(packet, ci->data);
 }
@@ -1328,7 +1328,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
         }
 
         clientid_mac_ptr = NULL;
-        if (!(opt & OPT_C) && !udhcp_find_option(client_data.options, DHCP_CLIENT_ID)) {
+        if (!(opt & OPT_C) && !udhcp_find_option(client_data.options, DHCP_CLIENT_ID, /*dhcpv6:*/ 0)) {
                 /* not suppressed and not set, create default client ID */
                 clientid_mac_ptr = udhcp_insert_new_option(
                                 &client_data.options, DHCP_CLIENT_ID,