I wrote: > > I have tried using LWIP_HOOK_DHCP_APPEND_OPTIONS() and > LWIP_HOOK_DHCP_PARSE_OPTION() to request additional DHCP options > from the server, using DHCP option 55 > (DHCP_OPTION_PARAMETER_REQUEST_LIST). > > At first I thought it was working fine. But on closer examination, it seems > the > server is not sending all requested options (e.g. options 3 and 6). That is > evidently because the DHCP request contains the option 55 twice (once from > the lwIP core code, a second time from my > LWIP_HOOK_DHCP_APPEND_OPTIONS()). According to the DHCP RFC 2131, " > Options may appear only once, unless otherwise specified in the options > document." So I guess the DHCP server (Microsoft in this case) is ignoring the > first occurrence of option 55. > > So, it would be good to improve the DHCP hook mechanism so that user code > can request additional options via option 55, without duplicating the option > contrary to the RFC. Ideally, it could be dynamic not a static array, so the > user > code could decide at run-time which additional options are requested. > > What would be a good way to improve the hook mechanism? > > (I'm interested in contributing some code back to the lwIP project, as long as > I have a rough idea what would be accepted.)
I worked out that in LWIP_HOOK_DHCP_APPEND_OPTIONS(), I can actually do a search through the existing options in msg->options[], looking for any pre-existing DHCP_OPTION_PARAMETER_REQUEST_LIST. Then I can insert the extra options into it. It's a bit fiddly, but I've got it working. Does that sound like a reasonable thing to do in LWIP_HOOK_DHCP_APPEND_OPTIONS()? -- Craig McQueen _______________________________________________ lwip-users mailing list lwip-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/lwip-users
