[git commit] udhcpc6: add some comments

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=e977853e70d4a8c346a1ad765fc8353ce0e2ced8
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

RFCs for DHCPv6 are written rather badly...

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 networking/udhcp/d6_common.h | 41 +++++++++++++++++++++++++++++------------
 networking/udhcp/d6_dhcpc.c  | 10 ++++++++++
 2 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/networking/udhcp/d6_common.h b/networking/udhcp/d6_common.h
index 9dfde7709..3cbfbb89e 100644
--- a/networking/udhcp/d6_common.h
+++ b/networking/udhcp/d6_common.h
@@ -63,28 +63,45 @@ struct d6_option {
 
 #define D6_OPT_CLIENTID       1
 #define D6_OPT_SERVERID       2
+/* "Identity Association for Non-temporary Addresses",
+ * also known as a "network interface" in plain English */
 #define D6_OPT_IA_NA          3
-#define D6_OPT_IA_TA          4
+/* "Identity Association for the Temporary Addresses".
+ * Presumably this is a "network interface with only link-local addresses".
+ * Why would DHCPv6 server assign such addresses, I have no idea. */
+//#define D6_OPT_IA_TA          4
+/* "IA Address", an IPv6 address */
 #define D6_OPT_IAADDR         5
+/* Option "Option Request Option". From the owners of a doggy dog named Dog? */
 #define D6_OPT_ORO            6
-#define D6_OPT_PREFERENCE     7
+//#define D6_OPT_PREFERENCE     7
 #define D6_OPT_ELAPSED_TIME   8
-#define D6_OPT_RELAY_MSG      9
-#define D6_OPT_AUTH          11
-#define D6_OPT_UNICAST       12
+//#define D6_OPT_RELAY_MSG      9
+//#define D6_OPT_AUTH          11
+/* "The server sends this option to a client to indicate to the client
+ * that it is allowed to unicast messages to the server."
+ * Contains IPv6 address to send packets to. */
+//#define D6_OPT_UNICAST       12
+/* "A Status Code option may appear in the options field of a DHCP
+ * message and/or in the options field of another option." */
 #define D6_OPT_STATUS_CODE   13
-#define D6_OPT_RAPID_COMMIT  14
-#define D6_OPT_USER_CLASS    15
-#define D6_OPT_VENDOR_CLASS  16
-#define D6_OPT_VENDOR_OPTS   17
-#define D6_OPT_INTERFACE_ID  18
-#define D6_OPT_RECONF_MSG    19
-#define D6_OPT_RECONF_ACCEPT 20
+/* "A client MAY include this option in a Solicit message if the client
+ * is prepared to perform the Solicit-Reply message exchange..." */
+//#define D6_OPT_RAPID_COMMIT  14	/* zero-length option */
+//#define D6_OPT_USER_CLASS    15
+//#define D6_OPT_VENDOR_CLASS  16
+//#define D6_OPT_VENDOR_OPTS   17
+//#define D6_OPT_INTERFACE_ID  18
+//#define D6_OPT_RECONF_MSG    19
+//#define D6_OPT_RECONF_ACCEPT 20
 
 #define D6_OPT_DNS_SERVERS   23
 #define D6_OPT_DOMAIN_LIST   24
 
+/* RFC 3633 "Identity Association for Prefix Delegation".
+ * This option says that client wants to get an IPv6 prefix */
 #define D6_OPT_IA_PD         25
+/* Response from the server comes in this one */
 #define D6_OPT_IAPREFIX      26
 
 /* RFC 4704 "The DHCPv6 Client FQDN Option"
diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index fd196eb67..9384e4b9c 100644
--- a/networking/udhcp/d6_dhcpc.c
+++ b/networking/udhcp/d6_dhcpc.c
@@ -1617,6 +1617,16 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 				prefix_timeout = 0;
 				option = d6_find_option(packet.d6_options, packet_end, D6_OPT_STATUS_CODE);
 				if (option && (option->data[0] | option->data[1]) != 0) {
+///FIXME:
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//    |       OPTION_STATUS_CODE      |         option-len            |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//    |          status-code          |                               |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
+//    .                        status-message                         .
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// so why do we think it's NAK if data[0] is zero but data[1] is not? That's wrong...
+// we should also check that option->len is ok (i.e. not 0), right?
 					/* return to init state */
 					bb_info_msg("received DHCP NAK (%u)", option->data[4]);
 					d6_run_script(packet.d6_options,