On Thu, Jul 18, 2019 at 12:44 PM Ulrich Windl < ulrich.wi...@rz.uni-regensburg.de> wrote:
> >>> Mantas Mikulenas <graw...@gmail.com> schrieb am 18.07.2019 um 10:06 in > Nachricht > <capwny8xs1jw9iu_a-tagnw-v0nqemacwdrpftpdekw_nfan...@mail.gmail.com>: > > On Thu, Jul 18, 2019 at 10:32 AM Ulrich Windl < > > ulrich.wi...@rz.uni-regensburg.de> wrote: > > > >> >>> Vaibhav Dahiya <vdah...@ncsu.edu> schrieb am 18.07.2019 um 02:53 in > >> Nachricht > >> <5d2fc2f0.1c69fb81.214d0.1...@mx.google.com>: > >> > Hello, > >> > > >> > I am using sd_journal_send api() api call to log messages on syslog > >> server. > >> > I see that this uses > >> > sendmsg(fd, &mh, MSG_NOSIGNAL) call. > >> > >> Aren't syslog messages UDP anyway? When would an UDP send block? > >> > > > > No, program APIs use Unix sockets (/dev/log, > /run/systemd/journal/socket). > > You only get UDP when your local syslog daemon is configured to forward > > elsewhere. > > > > That said, both are datagram sockets, I'm not sure whether sending to > Unix > > dgram sockets can block or not? > > ??? Datagram _is_ UDP > UDP is datagram, but datagram is not always UDP. "UDP" specifically means the datagram transport protocol that runs over IPv4/IPv6, nothing else. Unix sockets (AF_UNIX) have a datagram mode but they do not use UDP (or IP). Netlink is datagram-based but it isn't UDP-based. &c. -- Mantas Mikulėnas
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