[linux-next] LinuxNextTracking branch, master, updated. next-20170614

batman at open-mesh.org batman at open-mesh.org
Thu Jun 15 00:15:37 CEST 2017


The following commit has been merged in the master branch:
commit 8ea026b1601c68fd133c3f3b0350dd1cd59ae352
Author: Matthias Schiffer <mschiffer at universe-factory.net>
Date:   Wed Feb 22 17:25:41 2017 +0100

    batman-adv: decrease maximum fragment size
    
    With this patch the maximum fragment size is reduced from 1400 to 1280
    bytes.
    
    Fragmentation v2 correctly uses the smaller of 1400 and the interface
    MTU, thus generally supporting interfaces with an MTU < 1400 bytes, too.
    
    However, currently "Fragmentation v2" does not support re-fragmentation.
    Which means that once a packet is split into two packets of 1400 + x
    bytes for instance and the next hop provides an interface with an even
    smaller MTU of 1280 bytes, then the larger fragment is lost.
    
    A maximum fragment size of 1280 bytes is a safer option as this is the
    minimum MTU required by IPv6, making interfaces with an MTU < 1280
    rather exotic.
    
    Regarding performance, this should have no negative impact on unicast
    traffic: Having some more bytes in the smaller and some less in the
    larger does not change the sum of both fragments.
    
    Concerning TT, choosing 1280 bytes fragments might result in more TT
    messages than necessary when a large network is bridged into batman-adv.
    However, the TT overhead in general is marginal due to its reactive
    nature, therefore such a performance impact on TT should not be
    noticeable for a user.
    
    Cc: Matthias Schiffer <mschiffer at universe-factory.net>
    [linus.luessing at c0d3.blue: Added commit message]
    Signed-off-by: Linus L├╝ssing <linus.luessing at c0d3.blue>
    Signed-off-by: Sven Eckelmann <sven at narfation.org>
    Signed-off-by: Simon Wunderlich <sw at simonwunderlich.de>

diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index feaf60e4cbc3..2be8f1f46529 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -168,7 +168,7 @@ enum batadv_uev_type {
 /* Maximum number of fragments for one packet */
 #define BATADV_FRAG_MAX_FRAGMENTS 16
 /* Maxumim size of each fragment */
-#define BATADV_FRAG_MAX_FRAG_SIZE 1400
+#define BATADV_FRAG_MAX_FRAG_SIZE 1280
 /* Time to keep fragments while waiting for rest of the fragments */
 #define BATADV_FRAG_TIMEOUT 10000
 

-- 
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