Calling functions like recv() with a NULL buffer is not explicitly
allowed by the POSIX standard, so it must be avoided to be portable
across different libc implementations. Allocate an initial buffer before
handling requests, and also pass this buffer to the peek recv() call.
Fixes: 531937cf6f ("gluon-neighbour-info: fix broken output with large results")
Currently a buffer with a fixed size of 8192 bytes is used. However the
result can potentially be larger, which leads to a truncated JSON
output on stdout. UDP packets, without compression and with IP
fragmentation, can be up to 64KiB large.
Instead of using a fixed size buffer on the stack ask the kernel first
about the size of the UDP data and allocate a buffer of appropriate size
on the heap before receiving the UDP data.
The issue was observed with a custom respondd provider.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
End the process after one result in case -l is not given
and destination address is unicast.
Reduces singleshot execution time from timeout seconds to around 150ms.
resolves#2184
The timeout was calculated incorrectly (in each iteration the span between
the start time and the current time was substracted from the timeout
again), and would often become negative, causing warnings in the kernel
log.
