Hello again! I just realized that the wording was probably a bit off. What I wanted to ask is: why does FreeBSD kqueue implementation treat `SO_RCVLOWAT` as a raw packet size watermark, and not using the actual data size for filtering out events? I am totally fine with the fact that it triggers event on 0-size udp packets, but the behavior itself seems a bit odd, right? Please let me know if this is a bug, and I'll submit a patch. Cheers, Fedor. On Sat, Aug 2, 2014 at 2:57 PM, Fedor Indutny <fedor_at_indutny.com> wrote: > After reading that line more carefully, I wonder if this behavior is > really intentional here. > > It seems to me that `SO_RCVLOWAT` is supposed to set watermark value in > terms of > packet data bytes, not just raw packet size. And this is how `NOTE_LOWAT` > actually > works there, right? > > Could anyone please comment on this? Is it a bug? > > ---------------------- > > Regarding OSX: > > Submitted Apple Bug # 17894467 , with a patch. > > If anyone has friends at Apple who could help getting this in, please let > me know! > > Cheers, > Fedor. > > > On Sat, Aug 2, 2014 at 2:41 PM, Fedor Indutny <fedor_at_indutny.com> wrote: > >> Guess I know the answer: >> >> https://cloudup.com/cCkjLhI4M2r >> >> Basically, OSX is checking `kn_data` and FreeBSD is using >> `so->so_rcv.sb_cc`. >> >> Thank you anyway! >> >> >> On Sat, Aug 2, 2014 at 1:39 PM, Fedor Indutny <fedor_at_indutny.com> wrote: >> >>> Hello! >>> >>> I'm trying to figure out, why this code: >>> >>> https://github.com/indutny/0-udp >>> >>> Which basically sends a 0-length UDP packet to a server and polls >>> kqueue events on the server fd. >>> >>> Return 1 kevent on FreeBSD, and blocks indefinitely without >>> returning any events on OSX. >>> >>> So far I could see that FreeBSD and OSX are treating NOTE_LOWAT >>> differently: >>> >>> * >>> https://github.com/opensource-apple/xnu/blob/2fa84067f6cdeb23267f877ca4fd26201316da1b/bsd/kern/uipc_socket.c#L4461 >>> * >>> https://github.com/freebsd/freebsd/blob/6901832d8588537c81afbdb91d1a22deb5582c47/sys/kern/uipc_socket.c#L3163-L3164 >>> >>> FreeBSD's NOTE_LOWAT is overriding SO_RCVLOWAT, and OSX is using >>> SO_RVCLOWAT as a minimum value. But, since NOTE_LOWAT is not >>> involved here by default, I'm failing to see where exactly this >>> event could pass through kqueue filter. >>> >>> Could anyone with UDP and/or KQueue implementation knowledge >>> share some insights with me? >>> >>> Thank you very much! >>> Fedor. >>> >>> (NOTE: Duplicate, first email wasn't posted, because I wasn't subscribed >>> to the ML) >>> >> >> >Received on Sun Aug 24 2014 - 19:42:09 UTC
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