Red Hat Bugzilla – Bug 135125
telnet: 0: Name or service not known
Last modified: 2007-11-30 17:07:04 EST
Description of problem: "telnet 0 25" does not connect to localhost:25. Instead it throws an error "0: Name or service no known". Version-Release number of selected component (if applicable): telnet-0.17-26.i386.rpm How reproducible: fails every time Steps to Reproduce: 1. telnet 0 25 2. weep 3. weep some more Actual results: telnet: 0: Name or service not known Expected results: Trying 0.0.0.0... Connected to 0.0.0.0. Escape character is '^]'. 220 hostname ESMTP Sendmail 8.12.10/8.12.10; Fri, 8 Oct 2004 13:36:17 -0700 Additional info: For the past - Oh, I don't know, two decades? - 0 resolves to 127.0.0.1, and so "telnet 0 25" would connect to the local machine's smtp server, or "telnet 0 80" connects to the local HTTP server. Not so in RHEL3. WTF?
please provide: $ which telnet and do you have ipv6 enabled?
ipv6 is not enabled. Turns out the telnet in my path was /usr/kerberos/bin/telnet, but /usr/bin/telnet returns the same error. I believe this is not a bug in telnet after all, but glibc's gethostbyname(). In fact, it looks like this was broken intentionally in the glibc 2.3 series, for some reason. gethostbyname() no longer resolves undotted decimal addresses, or hexadecimal or octal addresses. It used to, but not anymore. "telnet 0 25" is one of the casualties.
Both gethostname ("0") and getaddrinfo ("0", NULL, NULL, &res); return the same thing as they used to. So the change is not in glibc.
well, nothing change in the source code of telnet
Retested. Works for me on a RHEL3-U3...
doh... fell in the trap... tested with /usr/kerberos/bin/telnet (which works) /usr/bin/telnet failed like described in the bug report.
With a RHEL3-U4 glibc: getaddrinfo("0", "25", 0xbfffe250, 0xbfffd9e4) = -2 gai_strerror(-2) = "Name or service not known"
Ok, this seems to be http://sources.redhat.com/bugzilla/show_bug.cgi?id=296
Should be fixed in glibc-2.3.2-95.32.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2005-256.html