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2018-03-10udhcpd: fix "not dying on SIGTERM"Denys Vlasenko
Fixes: commit 52a515d18724bbb34e3ccbbb0218efcc4eccc0a8 "udhcp: use poll() instead of select()" Feb 16 2017 udhcp_sp_read() is meant to check whether signal pipe indeed has some data to read. In the above commit, it was changed as follows: - if (!FD_ISSET(signal_pipe.rd, rfds)) + if (!pfds[0].revents) return 0; The problem is, the check was working for select() purely by accident. Caught signal interrupts select()/poll() syscalls, they return with EINTR (regardless of SA_RESTART flag in sigaction). _Then_ signal handler is invoked. IOW: they can't see any changes to fd state caused by signal haldler (in our case, signal handler makes signal pipe ready to be read). For select(), it means that rfds[] bit array is unmodified, bit of signal pipe's read fd is still set, and the above check "works": it thinks select() says there is data to read. This accident does not work for poll(): .revents stays clear, and we do not try reading signal pipe as we should. In udhcpd, we fall through and block in socket read. Further SIGTERM signals simply cause socket read to be interrupted and then restarted (since SIGTERM handler has SA_RESTART=1). Fixing this as follows: remove the check altogether. Set signal pipe read fd to nonblocking mode. Always read it in udhcp_sp_read(). If read fails, assume it's EAGAIN and return 0 ("no signal seen"). udhcpd avoids reading signal pipe on every recvd packet by looping if EINTR (using safe_poll()) - thus ensuring we have correct .revents for all fds - and calling udhcp_sp_read() only if pfds[0].revents!=0. udhcpc performs much fewer reads (typically it sleeps >99.999% of the time), there is no need to optimize it: can call udhcp_sp_read() after each poll unconditionally. To robustify socket reads, unconditionally set pfds[1].revents=0 in udhcp_sp_fd_set() (which is before poll), and check it before reading network socket in udhcpd. TODO: This might still fail: if pfds[1].revents=POLLIN, socket read may still block. There are rare cases when select/poll indicates that data can be read, but then actual read still blocks (one such case is UDP packets with wrong checksum). General advise is, if you use a poll/select loop, keep all your fds nonblocking. Maybe we should also do that to our network sockets? function old new delta udhcp_sp_setup 55 65 +10 udhcp_sp_fd_set 54 60 +6 udhcp_sp_read 46 36 -10 udhcpd_main 1451 1437 -14 udhcpc_main 2723 2708 -15 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 2/3 up/down: 16/-39) Total: -23 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-27tweak examples/var_service/*Denys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-15fix more instances of ": $((a++))" in shell scriptsDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-04-17Spelling fixes in comments, documentation, tests and examplesDenys Vlasenko
By klemens <ka7@github.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-01-03README_distro_proposal.txt: typo fixesTito Ragusa
Signed-off-by: Tito Ragusa <farmatito@tiscali.it> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-12-25Update to examples/var_service/README_distro_proposal.txtDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-12-03README_distro_proposal.txt: writeup about runit adoptionDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-10-14examples: update var_service/README againDenys Vlasenko
Added "ps -AH e" example Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-10-14typo fixes in docDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-10-14examples: update var_service/README againDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-10-14examples: update var_service/READMEDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-10-03examples: add example of a DHCP serverDenys Vlasenko
As usual, by multiplying directories - "dhcpd_eth0", "dhcpd_wlan1" you can run many servers on different interfaces. Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-09-26examples: wpa_supplicant.conf has a wrong field deleted in examplesDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-09-20examples/var_service/supplicant_if: new service exampleDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-07-30service/fw example: do not ruin $if[], use different nameDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-07-25var_service/fw: optionally flush all netdevs; optionally prefer one 0/0 routingDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-07-10examples: add a useful "see abridged log" script for ntpd service exampleDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-10-24tweak zcip service exampleDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-10-24Tweak READMEDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-10-24update network service examplesDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-10-24New example of a service: examples/var_service/zcip_ifDenys Vlasenko
Zeroconf for IPv4 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-10-15better pinger service exampleDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-03-31update example ntp.scriptDenys Vlasenko
Handle an interesting corner case when NTP server is reachable... but on a different IP now. Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2014-02-21Improve examples/var_service READMEsDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2010-12-08fix typo in READMEDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2010-12-06typo fixDenys Vlasenko
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
2010-12-06update examples/var_service/READMEDenys Vlasenko
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
2010-12-06add examples/var_service/READMEDenys Vlasenko
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
2010-01-26whitespace fixDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2010-01-25ntpd: explain why scripts can be run in quick successionDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2010-01-25whitespace fixesDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2010-01-18fix examples which used non-standard cut -b0-NNNDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2010-01-13examples: add example ntpd serviceDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-12-01ntpd: make it work w/o -g too :(Denys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-09fix 'not not' in commentDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-09tweak service examples a bit (less verbose comment in dhcp_if)Denys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-09tweak dhcp service example - add ntp configurationDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-08add and example of tftpd serviceDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-08add more service examplesDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-07tweak examplesDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-06whitespace fixesDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-11-06adding example runit-style service directoryDenys Vlasenko
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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