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*telnet* now accepts "-i" to use an IP address when calling *login*
When a computer on a network has multiple IP addresses, it was previously possible to use one address to connect to the *telnet* server, but the other addresses were saved in the `/var/run/utmp` file. To prevent the *telnet* utility from performing a DNS lookup and ensure that *telnet* uses a particular IP address when calling the *login* utility, you can now use the "-i" option. Note that "-i" works in the same way as the "-N" option on Debian systems.
Description of problem:
telnet is logging hostname in utmp not IP address.telnetd does not provide any option for remote connection to avoid dns calls.
Version-Release number of selected component (if applicable):
telnet-server-0.17-59.el7_2
How reproducible:
Always
Steps to Reproduce:
1.Create some remote connection from telnel client to server
2.On server then check utmp database utmpdump /var/run/utmp | grep "telnet user name"
3.It will show hostname in login records in utmp.
Actual results:
Currently telnet does not provide any option to avoid dns calls for remote logins.
Expected results:
It needs to be update in telnet.
Additional info:
Hi,
After share the test package having below patch it is successfully able to avoid dns calls.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>.
--- netkit-telnet-0.17/telnetd/telnetd.c 2016-03-19 15:30:52.292560751 +0530
+++ netkit-telnet-0.17_bkp/telnetd/telnetd.c 2016-03-20 09:20:04.311186347 +0530
@@ -87,6 +87,7 @@ int keepalive = 1;
char *loginprg = _PATH_LOGIN;
char *progname;
int lookupself = 1;
+int numeric_hosts=0;
extern void usage(void);
@@ -216,6 +217,7 @@ main(int argc, char *argv[], char *env[]
break;
case 'N':
+ numeric_hosts=1;
lookupself = 0;
break;
@@ -662,8 +664,7 @@ doit(struct sockaddr *who, socklen_t who
/* get name of connected client */
int error = -1;
char namebuf[255];
-
- error = getnameinfo(who, wholen, namebuf, sizeof(namebuf), NULL, 0, 0);
+ error = getnameinfo(who, wholen, namebuf, sizeof(namebuf), NULL, 0, numeric_hosts ? NI_NUMERICHOST : 0);
/* if we can't get a hostname now, settle for an address */
if(error == EAI_AGAIN)
@@ -676,8 +677,11 @@ doit(struct sockaddr *who, socklen_t who
exit(1);
}
- host = namebuf;
-
+ if (strncmp(namebuf, "::ffff:", sizeof("::ffff:") - 1) == 0)
+ host = namebuf + sizeof("::ffff:") - 1;
+ else
+ host = namebuf;
+
/*
* We must make a copy because Kerberos is probably going
* to also do a gethost* and overwrite the static data...
@@ -688,6 +692,7 @@ doit(struct sockaddr *who, socklen_t who
remote_host_name[sizeof(remote_host_name)-1] = 0;
/* Disallow funnies. */
+ if(!numeric_hosts)
for (i=0; remote_host_name[i]; i++) {
if (remote_host_name[i]<=32 || remote_host_name[i]>126)
remote_host_name[i] = '?';
>>>>>>>>>>>>>>>>>>>>>>>>>>>..
I think we can release same patch in official telnet errata along with update in man page also for -N option
>>>>>>>>>>>>>>>>>
-N Do not use DNS to canonicalize the local hostname; gethostname(2) returns a fully qualified name.
>>>>>>>>>>>>>>>>>>>>>>>>.
Regards
Mohit Agrawal
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHEA-2016-2543.html