bsc-nat: bsc_nat_filter_ipa: Improve documentation

Change-Id: I91b18aeb8bdc2a1b392474318b1df1b4b1fee5a3
diff --git a/openbsc/src/osmo-bsc_nat/bsc_filter.c b/openbsc/src/osmo-bsc_nat/bsc_filter.c
index 6a9e99f..ddfcdcb 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_filter.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_filter.c
@@ -135,6 +135,8 @@
 	return parsed;
 }
 
+/* Returns 0 if message is whitelisted (has to beforwarded by bsc-nat), 1 if
+/* it's blacklisted (not to be forwarded) */
 int bsc_nat_filter_ipa(int dir, struct msgb *msg, struct bsc_nat_parsed *parsed)
 {
 	int i;
@@ -177,7 +179,7 @@
 		}
 	}
 
-	/* go through the whitelust now */
+	/* go through the whitelist now */
 	for (i = 0; i < ARRAY_SIZE(white_list); ++i) {
 		/* ignore the rule? */
 		if (white_list[i].filter_dir != FILTER_TO_BOTH