MT#55283 report netlink errors by seq num

Not 100% sure if this is how it's intended to be handled, as the failed
requests seem to produce multiple ACK messages, but at least this fixes
the immediate problem of the printed error message not matching the
request which failed.

Closes #2041

Change-Id: I2a6bf57ce996c134b44d4f3484164a39c68fc93c

daemon/nftables.c

@@ -175,13 +175,13 @@ static char *iterate_rules(nfapi_socket *nl, int family, const char *chain,
 	if (!nfapi_send_buf(nl, b))
 		return g_strdup_printf("failed to write to netlink socket trying to read rules (%s) "
 				"(attempted: \"%s\")",
-				strerror(errno), nfapi_buf_msg(b));
+				strerror(errno), nfapi_err_msg(nl));
 
 	const char *err = nfapi_recv_iter(nl, &(nfapi_callbacks) { .rule = nftables_do_rule }, callbacks);
 	if (err)
 		return g_strdup_printf("error received from netlink socket reading rules (%s): %s "
 				"(attempted: \"%s\")",
-				strerror(errno), err, nfapi_buf_msg(b));
+				strerror(errno), err, nfapi_err_msg(nl));
 
 	if (callbacks->iterate_final) {
 		char *e = callbacks->iterate_final(nl, family, chain, callbacks);
@@ -219,13 +219,13 @@ static char *delete_rules(nfapi_socket *nl, int family, const char *chain,
 	if (!nfapi_send_buf(nl, b))
 		return g_strdup_printf("failed to write to netlink socket trying to delete rule (%s) "
 				"(attempted: \"%s\")",
-				strerror(errno), nfapi_buf_msg(b));
+				strerror(errno), nfapi_err_msg(nl));
 
 	const char *err = nfapi_recv_iter(nl, NULL, NULL);
 	if (err)
 		return g_strdup_printf("error received from netlink socket trying to delete rule (%s): %s "
 				"(attempted: \"%s\")",
-				strerror(errno), err, nfapi_buf_msg(b));
+				strerror(errno), err, nfapi_err_msg(nl));
 
 	return NULL;
 }
@@ -307,7 +307,7 @@ static char *add_chain(nfapi_socket *nl, int family, const char *chain,
 		if (err)
 			return g_strdup_printf("error returned from callback trying to add chain: %s "
 					"(attempted: \"%s\")",
-					err, nfapi_buf_msg(b));
+					err, nfapi_err_msg(nl));
 	}
 
 	nfapi_batch_end(b);
@@ -315,13 +315,13 @@ static char *add_chain(nfapi_socket *nl, int family, const char *chain,
 	if (!nfapi_send_buf(nl, b))
 		return g_strdup_printf("failed to write to netlink socket trying to add chain (%s) "
 				"(attempted: \"%s\")",
-				strerror(errno), nfapi_buf_msg(b));
+				strerror(errno), nfapi_err_msg(nl));
 
 	const char *err = nfapi_recv_iter(nl, NULL, NULL);
 	if (err)
 		return g_strdup_printf("error received from netlink socket trying to add chain (%s): %s "
 				"(attempted: \"%s\")",
-				strerror(errno), err, nfapi_buf_msg(b));
+				strerror(errno), err, nfapi_err_msg(nl));
 
 	return NULL;
 }
@@ -343,20 +343,20 @@ static char *add_rule(nfapi_socket *nl, int family,
 	if (err)
 		return g_strdup_printf("error returned from callback trying to add table: %s "
 				"(attempted: \"%s\")",
-				err, nfapi_buf_msg(b));
+				err, nfapi_err_msg(nl));
 
 	nfapi_batch_end(b);
 
 	if (!nfapi_send_buf(nl, b))
 		return g_strdup_printf("failed to write to netlink socket trying to add rule (%s) "
 				"(attempted: \"%s\")",
-				strerror(errno), nfapi_buf_msg(b));
+				strerror(errno), nfapi_err_msg(nl));
 
 	err = nfapi_recv_iter(nl, NULL, NULL);
 	if (err)
 		return g_strdup_printf("error received from netlink socket trying to add rule (%s): %s "
 				"(attempted: \"%s\")",
-				strerror(errno), err, nfapi_buf_msg(b));
+				strerror(errno), err, nfapi_err_msg(nl));
 
 	return NULL;
 }
@@ -625,13 +625,13 @@ static char *delete_chain(nfapi_socket *nl, int family, const char *chain) {
 	if (!nfapi_send_buf(nl, b))
 		return g_strdup_printf("failed to write to netlink socket trying to delete chain (%s) "
 				"(attempted: \"%s\")",
-				strerror(errno), nfapi_buf_msg(b));
+				strerror(errno), nfapi_err_msg(nl));
 
 	const char *err = nfapi_recv_iter(nl, NULL, NULL);
 	if (err)
 		return g_strdup_printf("error received from netlink socket trying to delete chain (%s): %s "
 				"(attempted: \"%s\")",
-				strerror(errno), err, nfapi_buf_msg(b));
+				strerror(errno), err, nfapi_err_msg(nl));
 
 	return NULL;
 }
@@ -715,13 +715,13 @@ static char *add_table(nfapi_socket *nl, int family) {
 	if (!nfapi_send_buf(nl, b))
 		return g_strdup_printf("failed to write to netlink socket trying to add table (%s) "
 				"(attempted: \"%s\")",
-				strerror(errno), nfapi_buf_msg(b));
+				strerror(errno), nfapi_err_msg(nl));
 
 	const char *err = nfapi_recv_iter(nl, NULL, NULL);
 	if (err)
 		return g_strdup_printf("error received from netlink socket trying to add table (%s): %s "
 				"(attempted: \"%s\")",
-				strerror(errno), err, nfapi_buf_msg(b));
+				strerror(errno), err, nfapi_err_msg(nl));
 
 	return NULL;
 }

lib/netfilter_api.c

@@ -19,6 +19,8 @@ struct nfapi_socket {
 	int fd;
 	struct sockaddr_nl addr; // local
 	uint16_t seq;
+	GHashTable *msgs;
+	uint16_t err_seq;
 };
 
 struct nfapi_buf {
@@ -55,6 +57,7 @@ nfapi_socket *nfapi_socket_open(void) {
 	nfapi_socket *s = g_new0(__typeof(*s), 1);
 	s->fd = fd;
 	s->addr = saddr;
+	s->msgs = g_hash_table_new_full(g_direct_hash, g_direct_equal, NULL, g_free);
 
 	return s;
 }
@@ -62,9 +65,15 @@ nfapi_socket *nfapi_socket_open(void) {
 void nfapi_socket_close(nfapi_socket *s) {
 	if (s->fd != -1)
 		close(s->fd);
+	g_hash_table_destroy(s->msgs);
 	g_free(s);
 }
 
+const char *nfapi_err_msg(nfapi_socket *s) {
+	const char *m = g_hash_table_lookup(s->msgs, GUINT_TO_POINTER(s->err_seq));
+	return m ?: "?";
+}
+
 
 nfapi_buf *nfapi_buf_new(nfapi_socket *s) {
 	nfapi_buf *b = g_new0(__typeof(*b), 1);
@@ -81,10 +90,6 @@ void nfapi_buf_free(nfapi_buf *b) {
 	g_free(b);
 }
 
-const char *nfapi_buf_msg(nfapi_buf *b) {
-	return b->readable->str;
-}
-
 
 static void readable_vadd(GString *r, const char *fmt, va_list va) {
 	if (r->len > 0)
@@ -193,6 +198,10 @@ void nfapi_nested_end(nfapi_buf *b) {
 
 
 bool nfapi_send_buf(nfapi_socket *s, nfapi_buf *b) {
+	char *msg = g_string_free(b->readable, FALSE);
+	g_hash_table_replace(s->msgs, GUINT_TO_POINTER(b->seq), msg);
+	b->readable = g_string_new("");
+
 	ssize_t ret = sendto(s->fd, b->s->str, b->s->len, 0, (struct sockaddr *) &zero_nl_sockaddr,
 			sizeof(zero_nl_sockaddr));
 	if (ret != b->s->len)
@@ -285,6 +294,7 @@ const char *nfapi_recv_iter(nfapi_socket *s, const nfapi_callbacks *c, void *use
 						return NULL;
 
 					errno = -err->error;
+					s->err_seq = hdr->nlmsg_seq;
 					return "error returned from netlink, see errno";
 				}
 				else

lib/netfilter_api.h

@@ -20,11 +20,11 @@ typedef struct {
 
 nfapi_socket *nfapi_socket_open(void);
 void nfapi_socket_close(nfapi_socket *);
+const char *nfapi_err_msg(nfapi_socket *);
 
 
 nfapi_buf *nfapi_buf_new(nfapi_socket *);
 void nfapi_buf_free(nfapi_buf *);
-const char *nfapi_buf_msg(nfapi_buf *);
 
 __attribute__ ((format(printf, 5, 6)))
 void nfapi_add_msg(nfapi_buf *, uint16_t type, uint16_t family, uint16_t flags, const char *fmt, ...);