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由 Linus Lüssing 提交于
DHCP connectivity issues can currently occur if the following conditions are met: 1) A DHCP packet from a client to a server 2) This packet has a multicast destination 3) This destination has a matching entry in the translation table (FF:FF:FF:FF:FF:FF for IPv4, 33:33:00:01:00:02/33:33:00:01:00:03 for IPv6) 4) The orig-node determined by TT for the multicast destination does not match the orig-node determined by best-gateway-selection In this case the DHCP packet will be dropped. The "gateway-out-of-range" check is supposed to only be applied to unicasted DHCP packets to a specific DHCP server. In that case dropping the the unicasted frame forces the client to retry via a broadcasted one, but now directed to the new best gateway. A DHCP packet with broadcast/multicast destination is already ensured to always be delivered to the best gateway. Dropping a multicasted DHCP packet here will only prevent completing DHCP as there is no other fallback. So far, it seems the unicast check was implicitly performed by expecting the batadv_transtable_search() to return NULL for multicast destinations. However, a multicast address could have always ended up in the translation table and in fact is now common. To fix this potential loss of a DHCP client-to-server packet to a multicast address this patch adds an explicit multicast destination check to reliably bail out of the gateway-out-of-range check for such destinations. The issue and fix were tested in the following three node setup: - Line topology, A-B-C - A: gateway client, DHCP client - B: gateway server, hop-penalty increased: 30->60, DHCP server - C: gateway server, code modifications to announce FF:FF:FF:FF:FF:FF Without this patch, A would never transmit its DHCP Discover packet due to an always "out-of-range" condition. With this patch, a full DHCP handshake between A and B was possible again. Fixes: be7af5cf ("batman-adv: refactoring gateway handling code") Signed-off-by: NLinus Lüssing <linus.luessing@c0d3.blue> Signed-off-by: NSven Eckelmann <sven@narfation.org> Signed-off-by: NSimon Wunderlich <sw@simonwunderlich.de>
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