Hi Eric,
On Tue, Feb 12, 2019 at 05:58:41PM -0800, Eric Dumazet wrote:
> In the past, we tried to increase the buffer size up to 32 KB in order
> to reduce number of syscalls per dump.
>
> Commit 2d34851cd341 ("lib/libnetlink: re malloc buff if size is not enough")
> brought the size back to 4KB because the kernel can not know the application
> is ready to receive bigger requests.
>
> See kernel commits 9063e21fb026 ("netlink: autosize skb lengthes") and
> d35c99ff77ec ("netlink: do not enter direct reclaim from netlink_dump()")
> for more details.
Wouldn't it be better if the kernel recognized MSG_TRUNC and allocated a
buffer large enough to hold the full message in that case? I have no
idea how hard that would be to implement, but calling recvmsg() with
MSG_TRUNC set and not getting the full message length in return is not
quite what one expects after reading recvmsg(2).
Cheers, Phil
