llmnrd: compare full hostname in query, fix off-by-one error

When checking whether the hostname matches, llmnrd does not consider the
last character of the hostnames, leading to the following incorrect
behavior:

$ ./llmnrd -H foobar
Starting llmnrd on port 5355, hostname foobar
...

$ ./llmnr-query foobaZ
LLMNR query: foobaZ IN ANY
LLMNR response: foobar IN A 10.42.0.42 (TTL 30)

Fix it by considering the full hostname. Also do only convert alphabetic
characters to lowercase using tolower(3), since its behavior is
undefined for any other characters.

Fixes #21
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

1 files changed, 8 insertions, 2 deletions

diff --git a/llmnr.c b/llmnr.c
index 64fcabd..0b35ae7 100644
--- a/llmnr.c
+++ b/llmnr.c
@@ -61,9 +61,15 @@ static bool llmnr_name_matches(const uint8_t *query)
 	if (query[1 + n] != 0)
 		return false;
 
-	for (i = 1; i < llmnr_hostname[0]; i++)
-		if (tolower(query[i]) != tolower(llmnr_hostname[i]))
+	for (i = 1; i <= n; i++) {
+		char a = query[i];
+		char b = llmnr_hostname[i];
+		a = isalpha(a) ? tolower(a) : a;
+		b = isalpha(b) ? tolower(b) : b;
+		if (a != b) {
 			return false;
+		}
+	}
 	return true;
 }