[PATCHv2 12/15] ident: use full dns names to generate email addresses

From: Jeff King <peff@peff.net>
Date: May 21, 2012, 23:10 UTC
Message-ID: <20120521231023.GL10981@sigill.intra.peff.net>
In-Reply-To: <20120521230917.GA474@sigill.intra.peff.net>

When we construct an email address from the username and hostname, we generate the host part of the email with this procedure:

  1. add the result of gethostname

  2. if it has a dot, ok, it's fully qualified

  3. if not, then look up the unqualified hostname via
     gethostbyname; take the domain name of the result and
     append it to the hostname

Step 3 can actually produce a bogus result, as the name returned by gethostbyname may not be related to the hostname we fed it (e.g., consider a machine "foo" with names "foo.one.example.com" and "bar.two.example.com"; we may have the latter returned and generate the bogus name "foo.two.example.com").

This patch simply uses the full hostname returned by gethostbyname. In the common case that the first part is the same as the unqualified hostname, the behavior is identical. And in the case that it is not the same, we are much more likely to be generating a valid name.

Signed-off-by: Jeff King <peff@peff.net>
---
 ident.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/ident.c b/ident.c
index 5aec073..b111e34 100644
--- a/ident.c
+++ b/ident.c
@@ -65,23 +65,18 @@ static void add_domainname(struct strbuf *out)
 {
 	char buf[1024];
 	struct hostent *he;
-	const char *domainname;
 
 	if (gethostname(buf, sizeof(buf))) {
 		warning("cannot get host name: %s", strerror(errno));
 		strbuf_addstr(out, "(none)");
 		return;
 	}
-	strbuf_addstr(out, buf);
 	if (strchr(buf, '.'))
-		return;
-
-	he = gethostbyname(buf);
-	strbuf_addch(out, '.');
-	if (he && (domainname = strchr(he->h_name, '.')))
-		strbuf_addstr(out, domainname + 1);
+		strbuf_addstr(out, buf);
+	else if ((he = gethostbyname(buf)) && strchr(he->h_name, '.'))
+		strbuf_addstr(out, he->h_name);
 	else
-		strbuf_addstr(out, "(none)");
+		strbuf_addf(out, "%s.(none)", buf);
 }
 
 static void copy_email(const struct passwd *pw, struct strbuf *email)

-- 
1.7.10.1.19.g711d603