Both OGMv1 (on the primary interface) and OGM2 unconditionally reallocated
their packet buffer on every transmission cycle, regardless of whether the
required size had changed. This meant a kfree/kmalloc pair even when the
TVLV payload size was identical to the previous send.
Introduce struct batadv_ogm_buf to encapsulate the OGM packet buffer
together with its current length, allocated capacity, and fixed header
length. This consolidates the separate buf/len arguments that were
previously threaded through each call site.
In batadv_tvlv_realloc_packet_buff(), the capacity is rounded up to the
next power of two so that small growth or shrinkage in TVLV data does not
trigger a reallocation. When kmalloc fails but the existing buffer is large
enough to hold the new data, the oversized buffer is reused rather than
returning an error.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
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