Lots of missing packets talking to a GigE camera: debugging suggestions? about aravis HOT 1 OPEN

I poked at this a bit more. In short, I wasn't setting the socket buffer size properly, and fixing that made it work.

Notes:

The socket buffer size can be set like this:

g_object_set (*stream,
              "socket-buffer",      ARV_GV_STREAM_SOCKET_BUFFER_FIXED,
              "socket-buffer-size", 20000000,
              NULL);

This sets the SO_RCVBUF setting on the socket. Described like this in
socket(7):

SO_RCVBUF
    Sets or gets the maximum socket receive buffer in bytes. The
    kernel doubles this value (to allow space for bookkeeping
    overhead) when it is set using setsockopt(2), and this doubled
    value is returned by getsockopt(2). The default value is set by
    the /proc/sys/net/core/rmem_default file, and the maximum allowed
    value is set by the /proc/sys/net/core/rmem_max file. The minimum
    (doubled) value for this option is 256.

The setting ends up in sk_rcvbuf in the kernel:

• https://lxr.linux.no/#linux+v6.7.1/net/core/sock.c#L1250
• https://lxr.linux.no/#linux+v6.7.1/net/core/sock.c#L960

Which is used in multiple places in https://lxr.linux.no/#linux+v6.7.1/net/ipv4/udp.c

If the data comes in faster than it can be read, it's stored in this buffer; if
the buffer is too small, the packets are thrown away. The logic and available
diagnostics are in the udp.c file linked above. /proc/net/snmp records the
dropped packets and there's a udp_fail_queue_rcv_skb tracepoint to catch some
paths.

The buffer size should be set to a bit more than the ArvBuffer payload size probably. I would guess aravis already does that by default, but it wasn't working on my machine. I'm going to take a look to get more detail in a bit.

from aravis.