Re: want blocking writes, but eventually get: errno 105 (No buffer space available)

[Tom Evans <tom_usenet@optusnet.com.au>]

On 23/06/16 01:18, ajneu wrote:
> ajneu <ajneu1 <at> gmail.com> writes:
>
>> My test-program blocks (in write) in the beginning (the 1st few
>> program-runs), but then after a number of program-restarts I eventually get:
>>     errno 105 (No buffer space available)
>> which is not acceptable, since I want to block (in the write), and not get
>> any error!!

Very old news. CAN is implemented "sort of like IP-over-Ethernet, and so has 
inherited the buffering from that system. So there's a NETBUF queue. When that 
one overflows you get ENOBUFS. So you can change it with:

     setsockopt(pSkt->skt, SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));

Other details here:

http://socket-can.996257.n3.nabble.com/Solving-ENOBUFS-returned-by-write-td2886.html

Search for ENOBUFS in this as well:

http://rtime.felk.cvut.cz/can/socketcan-qdisc-final.pdf

 > 1st program run:
 > ~> block on 33'rd write (32 frames queued)

You'll have the Network queue, the "tx_queue_len" in the driver, as well as 
however many physical message buffers there are in your hardware, which looks 
to be "32".

Tom