bionic: Support wildcards in cached hosts file

If an exact name is not found in the hosts file and the host name
contains at least one dot, search for entries of the form "*.domain",
where domain is the portion of the host name after the first dot.  If
that is not found, repeat using the domain.

Example: a.b.c.example.com would search for the following in turn:
	a.b.c.example.com
	*.b.c.example.com
	*.c.example.com
	*.example.com
	*.com

Change-Id: I4b0bb81699151d5b371850daebf785e35ec9b180

1 files changed, 28 insertions, 1 deletions

diff --git a/libc/dns/net/hosts_cache.c b/libc/dns/net/hosts_cache.c
index deafb78b7..5038986be 100644
--- a/libc/dns/net/hosts_cache.c
+++ b/libc/dns/net/hosts_cache.c
@@ -121,7 +121,7 @@ static int cmp_hcent_name(const void *a, const void *b)
 	return hstrcmp(na, nb);
 }
 
-static struct hcent *_hcfindname(const char *name)
+static struct hcent *_hcfindname_exact(const char *name)
 {
 	size_t first, last, mid;
 	struct hcent *cur = NULL;
@@ -162,6 +162,33 @@ found:
 	return cur;
 }
 
+static struct hcent *_hcfindname(const char *name)
+{
+	struct hcent *ent;
+	char namebuf[MAX_HOSTLEN];
+	char *p;
+	char *dot;
+
+	ent = _hcfindname_exact(name);
+	if (!ent && strlen(name) < sizeof(namebuf)) {
+		strcpy(namebuf, name);
+		p = namebuf;
+		do {
+			dot = strchr(p, '.');
+			if (!dot)
+				break;
+			if (dot > p) {
+				*(dot - 1) = '*';
+				ent = _hcfindname_exact(dot - 1);
+			}
+			p = dot + 1;
+		}
+		while (!ent);
+	}
+
+	return ent;
+}
+
 /*
  * Find next name on line, if any.
  *