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Bug#490530: libc6: gethostbyaddr() times out if reverse dns not found
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Bug#490530: libc6: gethostbyaddr() times out if reverse dns not found
by Thue Janus Kristensen
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Package: libc6
Version: 2.7-10 Severity: normal I noticed that when I tried pinging kalus.dk (which does not have reverse DNS at the time of writing), ping would only send a packet every 5 seconds. R@h ~> host kalus.dk kalus.dk has address 89.233.27.15 kalus.dk mail is handled by 10 mail.kalus.dk. R@h ~> host 89.233.27.15 Host 15.27.233.89.in-addr.arpa. not found: 3(NXDOMAIN) R@h ~> ping kalus.dk PING kalus.dk (89.233.27.15) 56(84) bytes of data. [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=1 ttl=56 time=6.21 ms [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=2 ttl=56 time=5.89 ms [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=3 ttl=56 time=5.98 ms [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=4 ttl=56 time=4.48 ms I tracked it down to the function call char *pr_addr in ping.c, when calling gethostbyaddr() : /* pr_addr -- Return an ascii host address as a dotted quad and optionally with a hostname. */ char *pr_addr(__u32 addr) { struct hostent *hp; [...] hp = gethostbyaddr((char *)&addr, 4, AF_INET); [...] } I see no reason why it should take 5 seconds to find out that reverse DNS is not available, when the "host" command returns the answer immediately. Doing a strace I get (selected parts of trace): stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=131, ...}) = 0 socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("83.221.148.2")}, 28) = 0 fcntl(4, F_GETFL) = 0x2 (flags O_RDWR) fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0 poll([{fd=4, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1 sendto(4, "\t,\1\0\0\1\0\0\0\0\0\0\00215\00227\003233\00289\7in-a"..., 43, MSG_NOSIGNAL, NULL, 0) = 43 poll([{fd=4, events=POLLIN, revents=POLLIN}], 1, 5000) = 1 ioctl(4, FIONREAD, [103]) = 0 recvfrom(4, "\t,\201\203\0\1\0\0\0\1\0\0\00215\00227\003233\00289\7"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("83.221.148.2")}, [16]) = 103 close(4) = 0 socket(PF_FILE, SOCK_STREAM, 0) = 4 fcntl(4, F_GETFD) = 0 fcntl(4, F_SETFD, FD_CLOEXEC) = 0 connect(4, {sa_family=AF_FILE, path="/var/run/avahi-daemon/socket"}, 110) = 0 fcntl(4, F_GETFL) = 0x2 (flags O_RDWR) fstat(4, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2afcdfb72000 lseek(4, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek) write(4, "RESOLVE-ADDRESS 89.233.27.15\n", 29) = 29 read(4, [***Here there is a 5 second wait***] "-15 Timeout reached\n", 1024) = 20 close(4) = 0 I noted the lseek(4, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek) Which seems suspecious. Regards, Thue -- System Information: Debian Release: lenny/sid APT prefers testing APT policy: (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 2.6.24-1-amd64 (SMP w/4 CPU cores) Locale: LANG=en_DK.UTF-8, LC_CTYPE=en_DK.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/bash Versions of packages libc6 depends on: ii libgcc1 1:4.3.1-2 GCC support library libc6 recommends no packages. -- debconf information: * glibc/upgrade: true glibc/restart-failed: * glibc/restart-services: openbsd-inetd exim4 cupsys cron atd -- To UNSUBSCRIBE, email to debian-bugs-dist-REQUEST@... with a subject of "unsubscribe". Trouble? Contact listmaster@... |
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Bug#490530: libc6: gethostbyaddr() times out if reverse dns not found
by Stephen Gran
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This one time, at band camp, Thue Janus Kristensen said:
> I noticed that when I tried pinging kalus.dk (which does not have > reverse DNS at the time of writing), ping would only send a packet > every 5 seconds. > > connect(4, {sa_family=AF_FILE, path="/var/run/avahi-daemon/socket"}, 110) = 0 > write(4, "RESOLVE-ADDRESS 89.233.27.15\n", 29) = 29 > read(4, > > [***Here there is a 5 second wait***] > > "-15 Timeout reached\n", 1024) = 20 > close(4) = 0 bug? -- ----------------------------------------------------------------- | ,''`. Stephen Gran | | : :' : sgran@... | | `. `' Debian user, admin, and developer | | `- http://www.debian.org | ----------------------------------------------------------------- |
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Bug#490530: libc6: gethostbyaddr() times out if reverse dns not found
by Thue Janus Kristensen
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Yes - reading the trace closer it is obviously an avahi bug.
Regards, Thue On Sat, Jul 12, 2008 at 3:12 PM, Stephen Gran <sgran@...> wrote: This one time, at band camp, Thue Janus Kristensen said: |
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Bug#490530: libc6: gethostbyaddr() times out if reverse dns not found
by Thue Janus Kristensen
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I investigated further, and this is arguably not a bug. Please close it.
Regards, Thue On Sat, Jul 12, 2008 at 3:17 PM, Thue Janus Kristensen <thuejk@...> wrote: Yes - reading the trace closer it is obviously an avahi bug. |
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Bug#490530: marked as done (libc6: gethostbyaddr() times out if reverse dns not found)
by Debian Bug Tracking System
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Your message dated Tue, 22 Jul 2008 16:34:04 +0200 with message-id <20080722143404.GA11540@...> and subject line Re: Bug#490530: libc6: gethostbyaddr() times out if reverse dns not found has caused the Debian Bug report #490530, regarding libc6: gethostbyaddr() times out if reverse dns not found to be marked as done. This means that you claim that the problem has been dealt with. If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. (NB: If you are a system administrator and have no idea what this message is talking about, this may indicate a serious mail system misconfiguration somewhere. Please contact owner@... immediately.) -- 490530: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=490530 Debian Bug Tracking System Contact owner@... with problems Package: libc6 Version: 2.7-10 Severity: normal I noticed that when I tried pinging kalus.dk (which does not have reverse DNS at the time of writing), ping would only send a packet every 5 seconds. R@h ~> host kalus.dk kalus.dk has address 89.233.27.15 kalus.dk mail is handled by 10 mail.kalus.dk. R@h ~> host 89.233.27.15 Host 15.27.233.89.in-addr.arpa. not found: 3(NXDOMAIN) R@h ~> ping kalus.dk PING kalus.dk (89.233.27.15) 56(84) bytes of data. [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=1 ttl=56 time=6.21 ms [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=2 ttl=56 time=5.89 ms [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=3 ttl=56 time=5.98 ms [5 second pause] 64 bytes from 89.233.27.15: icmp_seq=4 ttl=56 time=4.48 ms I tracked it down to the function call char *pr_addr in ping.c, when calling gethostbyaddr() : /* pr_addr -- Return an ascii host address as a dotted quad and optionally with a hostname. */ char *pr_addr(__u32 addr) { struct hostent *hp; [...] hp = gethostbyaddr((char *)&addr, 4, AF_INET); [...] } I see no reason why it should take 5 seconds to find out that reverse DNS is not available, when the "host" command returns the answer immediately. Doing a strace I get (selected parts of trace): stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=131, ...}) = 0 socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("83.221.148.2")}, 28) = 0 fcntl(4, F_GETFL) = 0x2 (flags O_RDWR) fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0 poll([{fd=4, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1 sendto(4, "\t,\1\0\0\1\0\0\0\0\0\0\00215\00227\003233\00289\7in-a"..., 43, MSG_NOSIGNAL, NULL, 0) = 43 poll([{fd=4, events=POLLIN, revents=POLLIN}], 1, 5000) = 1 ioctl(4, FIONREAD, [103]) = 0 recvfrom(4, "\t,\201\203\0\1\0\0\0\1\0\0\00215\00227\003233\00289\7"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("83.221.148.2")}, [16]) = 103 close(4) = 0 socket(PF_FILE, SOCK_STREAM, 0) = 4 fcntl(4, F_GETFD) = 0 fcntl(4, F_SETFD, FD_CLOEXEC) = 0 connect(4, {sa_family=AF_FILE, path="/var/run/avahi-daemon/socket"}, 110) = 0 fcntl(4, F_GETFL) = 0x2 (flags O_RDWR) fstat(4, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2afcdfb72000 lseek(4, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek) write(4, "RESOLVE-ADDRESS 89.233.27.15\n", 29) = 29 read(4, [***Here there is a 5 second wait***] "-15 Timeout reached\n", 1024) = 20 close(4) = 0 I noted the lseek(4, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek) Which seems suspecious. Regards, Thue -- System Information: Debian Release: lenny/sid APT prefers testing APT policy: (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 2.6.24-1-amd64 (SMP w/4 CPU cores) Locale: LANG=en_DK.UTF-8, LC_CTYPE=en_DK.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/bash Versions of packages libc6 depends on: ii libgcc1 1:4.3.1-2 GCC support library libc6 recommends no packages. -- debconf information: * glibc/upgrade: true glibc/restart-failed: * glibc/restart-services: openbsd-inetd exim4 cupsys cron atd On Sat, Jul 12, 2008 at 08:04:27PM +0200, Thue Janus Kristensen wrote: > I investigated further, and this is arguably not a bug. Please close it. Closing it with this mail. > Regards, Thue > > On Sat, Jul 12, 2008 at 3:17 PM, Thue Janus Kristensen <thuejk@...> > wrote: > > > Yes - reading the trace closer it is obviously an avahi bug. > > > > Regards, Thue > > > > On Sat, Jul 12, 2008 at 3:12 PM, Stephen Gran <sgran@...> wrote: > > > >> This one time, at band camp, Thue Janus Kristensen said: > >> > I noticed that when I tried pinging kalus.dk (which does not have > >> > reverse DNS at the time of writing), ping would only send a packet > >> > every 5 seconds. > >> > > >> > connect(4, {sa_family=AF_FILE, path="/var/run/avahi-daemon/socket"}, > >> 110) = 0 > >> > write(4, "RESOLVE-ADDRESS 89.233.27.15\n", 29) = 29 > >> > read(4, > >> > > >> > [***Here there is a 5 second wait***] > >> > > >> > "-15 Timeout reached\n", 1024) = 20 > >> > close(4) = 0 > >> > >> Not that glibc doesn't have similar problems, but surely that's an avahi > >> bug? > >> -- > >> ----------------------------------------------------------------- > >> | ,''`. Stephen Gran | > >> | : :' : sgran@... | > >> | `. `' Debian user, admin, and developer | > >> | `- http://www.debian.org | > >> ----------------------------------------------------------------- > >> > >> -----BEGIN PGP SIGNATURE----- > >> Version: GnuPG v1.4.6 (GNU/Linux) > >> > >> iD8DBQFIeK3MSYIMHOpZA44RAi50AJ9zsnX17sRcT1inG92VuFXFAUebIQCgxP6A > >> U47EBFj4aH7Fbt1Lofe4lQw= > >> =Xkeg > >> -----END PGP SIGNATURE----- > >> > >> > > .''`. Aurelien Jarno | GPG: 1024D/F1BCDB73 : :' : Debian developer | Electrical Engineer `. `' aurel32@... | aurelien@... `- people.debian.org/~aurel32 | www.aurel32.net |
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