telnet --bind

[Simon Josefsson]

Hi.  I'm trying to get Debian to use inetutils's telnet by default, and
one discrepency compared to their current implementation (netkit) was
the --bind parameter.  It seems useful, so I implemented it in inetutils
(see patch below).  It appears to work -- notice the different listen
addresses in the ss output below.

/Simon

jas@latte:~/src/inetutils/telnet$ ip a|grep 192
    inet 192.168.10.43/24 brd 192.168.10.255 scope global dynamic noprefixroute 
wlp2s0
    inet 192.168.10.49/24 scope global secondary wlp2s0
jas@latte:~/src/inetutils/telnet$ ./telnet -b 192.168.10.49 www.sjd.se 80
Trying 178.174.241.102...
Connected to www.sjd.se.
Escape character is '^]'.
^]
telnet> ^Z
[1]+  Stoppad                 ./telnet -b 192.168.10.49 www.sjd.se 80
jas@latte:~/src/inetutils/telnet$ sudo ss|grep 102|tail -1
tcp   ESTAB      0      0                                192.168.10.49:46993    
                               178.174.241.102:http                             
jas@latte:~/src/inetutils/telnet$ fg
./telnet -b 192.168.10.49 www.sjd.se 80
quit
Connection closed.
jas@latte:~/src/inetutils/telnet$ ./telnet -b 192.168.10.43 www.sjd.se 80
Trying 178.174.241.102...
Connected to www.sjd.se.
Escape character is '^]'.
^]
telnet> ^Z
[1]+  Stoppad                 ./telnet -b 192.168.10.43 www.sjd.se 80
jas@latte:~/src/inetutils/telnet$ sudo ss|grep 102|tail -1
tcp   ESTAB      0      0                                192.168.10.43:45907    
                               178.174.241.102:http                             
jas@latte:~/src/inetutils/telnet$ fg
./telnet -b 192.168.10.43 www.sjd.se 80
quit
Connection closed.
jas@latte:~/src/inetutils/telnet$ 

Simon Josefsson via Commit-inetutils <commit-inetutils@gnu.org> writes:

> This is an automated email from the git hooks/post-receive script. It was
> generated because a ref change was pushed to the repository containing
> the project "GNU Inetutils ".
>
> The branch, master has been updated
>        via  f70b506e3746bce45d1b684d5ac5ef513af73df4 (commit)
>       from  4587969cf6aa0da90508ff1e3fd7976420ee3e7c (commit)
>
> Those revisions listed above that are new to this repository have
> not appeared on any other notification email; so we list those
> revisions in full, below.
>
> - Log -----------------------------------------------------------------
> http://git.savannah.gnu.org/cgit/inetutils.git/commit/?id=f70b506e3746bce45d1b684d5ac5ef513af73df4
>
>
> commit f70b506e3746bce45d1b684d5ac5ef513af73df4
> Author: Simon Josefsson <simon@josefsson.org>
> Date:   Wed Apr 28 20:14:09 2021 +0200
>
>     telnet: Support --bind (-b) for NetKit compatibility.
>     
>     * NEWS: Add.
>     * doc/inetutils.texi (telnet invocation): Add --bind (-b).
>     * telnet/commands.c (tn): New variables hostaddr and srchostp.
>     Parse -b parameter.  Update usage string.  If -b is set, call
>     getaddrinfo on it and pass that ai_addr on to bind.
>     * telnet/main.c (srcaddr): New global variable.
>     (argp_options): Add --bind (-b).
>     (parse_opt): Set srcaddr to -b value.
>     (main): Propagate -b value to tn function.
>
> diff --git a/ChangeLog b/ChangeLog
> index 3c0f942..ad515b1 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,3 +1,16 @@
> +2021-04-28  Simon Josefsson  <simon@josefsson.org>
> +
> +     telnet: Support --bind (-b) for NetKit compatibility.
> +     * NEWS: Add.
> +     * doc/inetutils.texi (telnet invocation): Add --bind (-b).
> +     * telnet/commands.c (tn): New variables hostaddr and srchostp.
> +     Parse -b parameter.  Update usage string.  If -b is set, call
> +     getaddrinfo on it and pass that ai_addr on to bind.
> +     * telnet/main.c (srcaddr): New global variable.
> +     (argp_options): Add --bind (-b).
> +     (parse_opt): Set srcaddr to -b value.
> +     (main): Propagate -b value to tn function.
> +
>  2021-02-11  Simon Josefsson  <simon@josefsson.org>
>  
>       * TODO: Add items discussed on mailing list.
> diff --git a/NEWS b/NEWS
> index 6d3c9af..1f13094 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -2,6 +2,12 @@ GNU inetutils NEWS -- history of user-visible changes.
>  
>  * Noteworthy changes in release ?.? (????-??-??) [?]
>  
> +* telnet
> +
> +** Implement --bind (-b).
> +
> +This is used to bind to a particular local socket, for compatibility
> +with NetKit's telnet.
>  
>  * Noteworthy changes in release 2.0 (2021-02-05) [stable]
>  
> diff --git a/doc/inetutils.texi b/doc/inetutils.texi
> index 5fb7675..ba7c9d2 100644
> --- a/doc/inetutils.texi
> +++ b/doc/inetutils.texi
> @@ -2996,6 +2996,12 @@ Use an 8-bit data path.
>  @opindex --login
>  Attempt automatic login.
>  
> +@item -b @var{address}
> +@itemx --bind=@var{address}
> +@opindex -b
> +@opindex --bind
> +Bind to specific local @var{address}.
> +
>  @item -c
>  @itemx --no-rc
>  @opindex -c
> diff --git a/telnet/commands.c b/telnet/commands.c
> index 36a951e..5cc9b4d 100644
> --- a/telnet/commands.c
> +++ b/telnet/commands.c
> @@ -2449,7 +2449,7 @@ int
>  tn (int argc, char *argv[])
>  {
>  #ifdef IPV6
> -  struct addrinfo *result, *aip, hints;
> +  struct addrinfo *result, *aip, hints, *hostaddr;
>  #else
>    struct hostent *host = 0;
>    struct sockaddr_in sin;
> @@ -2458,7 +2458,7 @@ tn (int argc, char *argv[])
>  #endif
>    const int on = 1;
>    int err;
> -  char *cmd, *hostp = 0, *portp = 0, *user = 0;
> +  char *cmd, *hostp = 0, *portp = 0, *user = 0, *srchostp = 0;
>  #if defined HAVE_IDN || defined HAVE_IDN2
>    char *hosttmp = 0;
>  #endif
> @@ -2506,6 +2506,16 @@ tn (int argc, char *argv[])
>         --argc;
>         continue;
>       }
> +      if (strcmp (*argv, "-b") == 0)
> +     {
> +       --argc;
> +       ++argv;
> +       if (argc == 0)
> +         goto usage;
> +       srchostp = *argv++;
> +       --argc;
> +       continue;
> +     }
>        if (strcmp (*argv, "-a") == 0)
>       {
>         --argc;
> @@ -2546,7 +2556,7 @@ tn (int argc, char *argv[])
>         continue;
>       }
>      usage:
> -      printf ("usage: %s [-4] [-6] [-l user] [-a] host-name [port]\n", cmd);
> +      printf ("usage: %s [-4] [-6] [-l user] [-b addr] [-a] host-name 
> [port]\n", cmd);
>        return 0;
>      }
>    if (hostp == 0)
> @@ -2624,6 +2634,18 @@ tn (int argc, char *argv[])
>    hints.ai_flags = AI_IDN;
>  # endif
>  
> +  if (srchostp)
> +    {
> +      err = getaddrinfo (srchostp, "0", &hints, &hostaddr);
> +      if (err < 0)
> +     {
> +       printf ("Could not resolve %s: %s\n", srchostp,
> +               gai_strerror (err));
> +       return 0;
> +     }
> +      hints.ai_family = hostaddr->ai_family;
> +    }
> +
>    err = getaddrinfo (hostp, portp, &hints, &result);
>    if (err)
>      {
> @@ -2669,6 +2691,16 @@ tn (int argc, char *argv[])
>         return 0;
>       }
>  
> +      if (srchostp)
> +     {
> +       err = bind(net, hostaddr->ai_addr, hostaddr->ai_addrlen);
> +       if (err < 0)
> +         {
> +           perror ("telnet: bind");
> +           return 0;
> +         }
> +     }
> +
>        if (debug)
>       {
>         err = setsockopt (net, SOL_SOCKET, SO_DEBUG, &on, sizeof (on));
> @@ -2698,6 +2730,8 @@ tn (int argc, char *argv[])
>      }
>    while (!connected);
>  
> +  if (srchostp)
> +    freeaddrinfo(hostaddr);
>    freeaddrinfo (result);
>  #else /* !IPV6 */
>    temp = inet_addr (hostp);
> diff --git a/telnet/main.c b/telnet/main.c
> index a80d3c3..c790d6e 100644
> --- a/telnet/main.c
> +++ b/telnet/main.c
> @@ -105,7 +105,7 @@ tninit (void)
>  }
>
>  int family = 0;
> -char *user;
> +char *user, *srcaddr;
>  #ifdef       FORWARD
>  extern int forward_flags;
>  #endif /* FORWARD */
> @@ -132,6 +132,8 @@ static struct argp_option argp_options[] = {
>    /* FIXME: Called "8bit" in r* utils */
>    { "binary", '8', NULL, 0,
>      "use an 8-bit data transmission", GRID+1 },
> +  { "bind", 'b', "ADDRESS", 0,
> +    "bind to specific local ADDRESS", GRID+1 },
>    { "login", 'a', NULL, 0,
>      "attempt automatic login", GRID+1 },
>    { "no-rc", 'c', NULL, 0,
> @@ -313,6 +315,10 @@ parse_opt (int key, char *arg, struct argp_state *state 
> _GL_UNUSED_PARAMETER)
>        break;
>  #endif
>  
> +    case 'b':
> +      srcaddr = arg;
> +      break;
> +
>      default:
>        return ARGP_ERR_UNKNOWN;
>      }
> @@ -374,7 +380,7 @@ main (int argc, char *argv[])
>      {
>        /* The command line contains at least one argument.
>         */
> -      char *args[8], **argp = args;
> +      char *args[10], **argp = args;
>  
>        if (argc > 2)
>       error (EXIT_FAILURE, 0, "too many arguments");
> @@ -384,6 +390,11 @@ main (int argc, char *argv[])
>         *argp++ = "-l";
>         *argp++ = user;
>       }
> +      if (srcaddr)
> +     {
> +       *argp++ = "-b";
> +       *argp++ = srcaddr;
> +     }
>        if (family == 4)
>       *argp++ = "-4";
>        else if (family == 6)
>
> -----------------------------------------------------------------------
>
> Summary of changes:
>  ChangeLog          | 13 +++++++++++++
>  NEWS               |  6 ++++++
>  doc/inetutils.texi |  6 ++++++
>  telnet/commands.c  | 40 +++++++++++++++++++++++++++++++++++++---
>  telnet/main.c      | 15 +++++++++++++--
>  5 files changed, 75 insertions(+), 5 deletions(-)
>
>
> hooks/post-receive

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