[PATCH nft] src: compute mnemonic port name much easier

[Jan Engelhardt <jengelh@xxxxxxx>]

Signed-off-by: Jan Engelhardt <jengelh@xxxxxxx>
---
 src/datatype.c | 34 ++++++----------------------------
 src/json.c     | 20 +++++---------------
 2 files changed, 11 insertions(+), 43 deletions(-)

diff --git a/src/datatype.c b/src/datatype.c
index 189e1b48..e4ef51e8 100644
--- a/src/datatype.c
+++ b/src/datatype.c
@@ -657,34 +657,12 @@ const struct datatype inet_protocol_type = {
 
 static void inet_service_print(const struct expr *expr, struct output_ctx *octx)
 {
-	struct sockaddr_in sin = { .sin_family = AF_INET };
-	char buf[NI_MAXSERV];
-	uint16_t port;
-	int err;
-
-	sin.sin_port = mpz_get_be16(expr->value);
-	err = getnameinfo((struct sockaddr *)&sin, sizeof(sin), NULL, 0,
-			  buf, sizeof(buf), 0);
-	if (err != 0) {
-		nft_print(octx, "%u", ntohs(sin.sin_port));
-		return;
-	}
-	port = atoi(buf);
-	/* We got a TCP service name string, display it... */
-	if (htons(port) != sin.sin_port) {
-		nft_print(octx, "\"%s\"", buf);
-		return;
-	}
-
-	/* ...otherwise, this might be a UDP service name. */
-	err = getnameinfo((struct sockaddr *)&sin, sizeof(sin), NULL, 0,
-			  buf, sizeof(buf), NI_DGRAM);
-	if (err != 0) {
-		/* No service name, display numeric value. */
-		nft_print(octx, "%u", ntohs(sin.sin_port));
-		return;
-	}
-	nft_print(octx, "\"%s\"", buf);
+	uint16_t port = mpz_get_be16(expr->value);
+	const struct servent *s = getservbyport(port, NULL);
+	if (s == NULL)
+		nft_print(octx, "%hu", ntohs(port));
+	else
+		nft_print(octx, "\"%s\"", s->s_name);
 }
 
 void inet_service_type_print(const struct expr *expr, struct output_ctx *octx)
diff --git a/src/json.c b/src/json.c
index 1906e7db..7be13e6e 100644
--- a/src/json.c
+++ b/src/json.c
@@ -1021,23 +1021,13 @@ json_t *inet_protocol_type_json(const struct expr *expr,
 
 json_t *inet_service_type_json(const struct expr *expr, struct output_ctx *octx)
 {
-	struct sockaddr_in sin = {
-		.sin_family = AF_INET,
-		.sin_port = mpz_get_be16(expr->value),
-	};
-	char buf[NI_MAXSERV];
+	uint16_t port = mpz_get_be16(expr->value);
+	const struct servent *s = NULL;
 
 	if (!nft_output_service(octx) ||
-	    getnameinfo((struct sockaddr *)&sin, sizeof(sin),
-		        NULL, 0, buf, sizeof(buf), 0))
-		return json_integer(ntohs(sin.sin_port));
-
-	if (htons(atoi(buf)) == sin.sin_port ||
-	    getnameinfo((struct sockaddr *)&sin, sizeof(sin),
-			NULL, 0, buf, sizeof(buf), NI_DGRAM))
-		return json_integer(ntohs(sin.sin_port));
-
-	return json_string(buf);
+	    (s = getservbyport(port, NULL)) == NULL)
+		return json_integer(ntohs(port));
+	return json_string(s->s_name);
 }
 
 json_t *mark_type_json(const struct expr *expr, struct output_ctx *octx)
-- 
2.25.0