Various DHCP clients on OpenWrt, can someone tell me the difference?

fakemanhk · February 14, 2024, 5:39am

I understand that OpenWrt default is odhcpc6 (for IPv6), but looking into GitHub issues, and various reports about folks in Japan using NTT 10G having a "8-hour disconnection" and finding that might be problem of odhcpc6 (well, I also want to eliminate the problem), I am trying to look for other DHCP clients on WAN side.

Looking into package list, I found 2 more:

isc-dhcp-client-ipv6
dhcpcd

The former one doesn't get any IPv6 address from upstream router, I have no idea why. The later one not tested yet but will try soon, so I want to know their difference? My goal is to get PD from ISP and then delegate to downstream (with ND Proxy)

lleachii · February 14, 2024, 6:57am

One is made by the Internet Systems Consortium
One made by https://roy.marples.name/

Just to be clear, the ISC implementations of DHCP became end-of-life in October 2022. See (no client);

This works with the default odhcpc6 with a standard image. Are you having some issue with setting up IPv6 in the official images with odhcpc6?

Can you provide a reference?

If there's an issue, I'm sure we'd like to know as well.

fakemanhk · February 14, 2024, 7:02am

Here is the problem mentioned in GitHub

github.com/openwrt/openwrt

[odhcp6c] DHCPv6 client loses connection every 8 hours(after the second expiration of PD valid lifetime) on on Japan NTT 10G Hikari

opened 04:54PM - 14 Sep 23 UTC

missing233

bug

### Describe the bug The issue seems like [this](https://github.com/openwrt/o…dhcp6c/issues/61) I'm using OpenWRT with NTT 10G Hikari (Flets Cross). I've encountered a specific issue regarding the DHCPv6 PD. From the NTT DHCPv6 server, my DHCPv6 Client has been assigned a /56 PD prefix with the following lifetimes: ``` T1: 7200 T2: 10800 Preferred Lifetime: 12600 Valid Lifetime: 14400 ``` The problem manifests itself at specific intervals — typically at the the 8-hour marks. Just when NTT's DHCPv6 server sends out a reconfigure message, within about a second, I get a notice: `'daemon.notice netifd: Interface 'wan6' has lost the connection'.` The connection will restore in about 10 seconds. In the packet capture data during this process, it shows that at the 28,800-second mark (8 hours), the DHCPv6 server sent a Reconfigure Message to the client. Subsequently, within less than a second, the wan6 connection was lost. This was immediately followed by the Solicit Message and Request Message. Interestingly, the likelihood of encountering this issue at the 14,400-second mark (4 hours) is almost negligible. When the DHCPv6 server sends a Reconfigure Message at this time, odhcp6c successfully responds with a Renew Message. The issue is most likely to occur at the 8-hour mark, which is when the second valid lifetime expires. My ISP uses an IPv4 over IPv6 protocol, requiring a special IPv6 address as a tunnel endpoint. This issue only pops up when I assign this particular IPv6 address to the IPv4 over IPv6 tunnel interface (by using option ip6ifaceid). The ISP provided me with a router XG-100NE(OEM by NEC Platforms), it's rock solid. I've also done packet capture analysis on it. I've noticed that each Renew Message behaves differently from OpenWRT, and the response time seems to be a few seconds later than the ISP router. OpenWRT: ``` Identity Association for Prefix Delegation Option: Identity Association for Prefix Delegation (25) Length: 41 IAID: 00000001 T1: 0 T2: 0 IA Prefix Option: IA Prefix (26) Length: 25 Preferred lifetime: 0 Valid lifetime: 0 Prefix length: 56 Prefix address: 2400:xxxx:xxxx:xx00:: ``` ISP router: ``` Identity Association for Prefix Delegation Option: Identity Association for Prefix Delegation (25) Length: 41 IAID: 00000000 T1: 7200 T2: 10800 IA Prefix Option: IA Prefix (26) Length: 25 Preferred lifetime: 12600 Valid lifetime: 14400 Prefix length: 56 Prefix address: 2400:xxxx:xxxx:xx00:: ``` ### OpenWrt version r23763-46ed38adeb ### OpenWrt target/subtarget x86_64 ### Device GoWin Solution R86S - Intel(R) Pentium(R) Silver N6005 @ 2.00GHz : 4 Core 4 Thread ### Image kind Official downloaded image ### Steps to reproduce Using Japan's NTT FLET'S HIKARI CROSS, set WAN6 as a DHCPv6 client and assign an ifaceid to the WAN6 interface. ### Actual behaviour After two Valid lifetime expirations, WAN6 lost connection. ### Expected behaviour Make odhcp6c work properly ### Additional info Alright, I've set up a crontab scheduled task to make odhcp6c send Renew Message to update the IPv6 lifetime every hour. It seems to work, but I don't think it is a good solution. ### Diffconfig _No response_ ### Terms - [X] I am reporting an issue for OpenWrt, not an unsupported fork.

Borromini · February 14, 2024, 9:48am

That sounds like a daemon, not like a client (compare with odhcpd which by defaults acts as a DHCP v6 server on OpenWrt, and can be set to act as a DHCP v4 server as well instead of dnsmasq).

The C in odhcpc6 indicates it's a client.