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author | Linus Lüssing <linus.luessing@c0d3.blue> | 2018-03-22 00:21:32 +0100 |
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committer | Simon Wunderlich <sw@simonwunderlich.de> | 2018-03-24 10:25:49 +0100 |
commit | a752c0a4524889cdc0765925258fd1fd72344100 (patch) | |
tree | 67eea96738ad66b0542292b46f9574222daa60e6 /net/mpls/mpls_iptunnel.c | |
parent | f8fb3419ead44f9a3136995acd24e35da4525177 (diff) | |
download | linux-stable-a752c0a4524889cdc0765925258fd1fd72344100.tar.gz linux-stable-a752c0a4524889cdc0765925258fd1fd72344100.tar.bz2 linux-stable-a752c0a4524889cdc0765925258fd1fd72344100.zip |
batman-adv: fix packet loss for broadcasted DHCP packets to a server
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: be7af5cf9cae ("batman-adv: refactoring gateway handling code")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Diffstat (limited to 'net/mpls/mpls_iptunnel.c')
0 files changed, 0 insertions, 0 deletions