general/7170: ap_get_local_host() fails to retrieve proper IP address

[Danek Duvall <dd...@eng.sun.com>]

>Number:         7170
>Category:       general
>Synopsis:       ap_get_local_host() fails to retrieve proper IP address
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    apache
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Wed Jan 31 14:50:01 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     dduvall@eng.sun.com
>Release:        1.3.17
>Organization:
apache
>Environment:
This is on Solaris 8.
>Description:
If I run apache (1.3.17, but earlier releases do this as well) on my Solaris
box without specifying a ServerName, then I get a message saying that it's
defaulting to 127.0.0.1 and to please set ServerName.  This happens despite the
fact that while no FQDN is available, it's perfectly possible to get an IP
address for the machine.  The code simply fails to extract it properly.

The failing code is the clause that starts on line 2051 of main/util.c:

    if (!str && p->h_addr_list[0]) {
        ap_snprintf(str, sizeof(str), "%pA", p->h_addr_list[0]);
        server_hostname = ap_pstrdup(a, str);
        /* We will drop through to report the IP-named server */
    }

It's not clear to me why the test for !str exists.  If you've gotten to this
point, then str won't be NULL.  Is it expected that gethostbyname() will clear
it on failure?  If so, this doesn't happen on Solaris.

Even if it were to execute the body of this if statement, it still won't work
properly.  You need code something like the following:

    struct in_addr in;
    memcpy(&in.s_addr, p->h_addr_list[0], sizeof(in.s_addr));
    snprintf(str, sizeof(str), "%s", inet_ntoa(in));
    server_hostname = strdup(str);

This properly gives me my IP address.  I don't understand how %pA is supposed to
give a valid IP address.  It gives something you can telnet to under Linux (but
not Solaris), but it's not the right machine ...
>How-To-Repeat:
The reason I'm seeing this is that my /etc/hosts file contains no entries for my
IP address that contain dots, so the find_fqdn() function fails, and it tries to
fall back on an IP address.  It's easy to patch the code to make it fail all the
time (just to test the IP address retrieval).
>Fix:
That body of code should probably read something like this:

    if (p->h_addr_list[0]) {
        struct in_addr in;
        memcpy(&in.s_addr, p->h_addr_list[0], sizeof(in.s_addr));
        snprintf(str, sizeof(str), "%s", inet_ntoa(in));
        server_hostname = strdup(str);
    }
>Release-Note:
>Audit-Trail:
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