lib: Extract from devlink/mnlg a helper, mnlu_socket_recv_run()

Receiving a message in libmnl is a somewhat involved operation. Devlink's
mnlg library has an implementation that is going to be handy for other
tools as well. Extract it into a new helper.

Signed-off-by: Petr Machata <me@pmachata.org>
Signed-off-by: David Ahern <dsahern@gmail.com>

devlink/mnlg.c

@@ -28,7 +28,6 @@ struct mnlg_socket {
 	uint32_t id;
 	uint8_t version;
 	unsigned int seq;
-	unsigned int portid;
 };
 
 static struct nlmsghdr *__mnlg_msg_prepare(struct mnlg_socket *nlg, uint8_t cmd,
@@ -57,61 +56,10 @@ int mnlg_socket_send(struct mnlg_socket *nlg, const struct nlmsghdr *nlh)
 	return mnl_socket_sendto(nlg->nl, nlh, nlh->nlmsg_len);
 }
 
-static int mnlg_cb_noop(const struct nlmsghdr *nlh, void *data)
-{
-	return MNL_CB_OK;
-}
-
-static int mnlg_cb_error(const struct nlmsghdr *nlh, void *data)
-{
-	const struct nlmsgerr *err = mnl_nlmsg_get_payload(nlh);
-
-	/* Netlink subsystems returns the errno value with different signess */
-	if (err->error < 0)
-		errno = -err->error;
-	else
-		errno = err->error;
-
-	if (nl_dump_ext_ack(nlh, NULL))
-		return MNL_CB_ERROR;
-
-	return err->error == 0 ? MNL_CB_STOP : MNL_CB_ERROR;
-}
-
-static int mnlg_cb_stop(const struct nlmsghdr *nlh, void *data)
-{
-	int len = *(int *)NLMSG_DATA(nlh);
-
-	if (len < 0) {
-		errno = -len;
-		nl_dump_ext_ack_done(nlh, len);
-		return MNL_CB_ERROR;
-	}
-	return MNL_CB_STOP;
-}
-
-static mnl_cb_t mnlg_cb_array[NLMSG_MIN_TYPE] = {
-	[NLMSG_NOOP]	= mnlg_cb_noop,
-	[NLMSG_ERROR]	= mnlg_cb_error,
-	[NLMSG_DONE]	= mnlg_cb_stop,
-	[NLMSG_OVERRUN]	= mnlg_cb_noop,
-};
-
 int mnlg_socket_recv_run(struct mnlg_socket *nlg, mnl_cb_t data_cb, void *data)
 {
-	int err;
+	return mnlu_socket_recv_run(nlg->nl, nlg->seq, nlg->buf, MNL_SOCKET_BUFFER_SIZE,
-
+				    data_cb, data);
-	do {
-		err = mnl_socket_recvfrom(nlg->nl, nlg->buf,
-					  MNL_SOCKET_BUFFER_SIZE);
-		if (err <= 0)
-			break;
-		err = mnl_cb_run2(nlg->buf, err, nlg->seq, nlg->portid,
-				  data_cb, data, mnlg_cb_array,
-				  ARRAY_SIZE(mnlg_cb_array));
-	} while (err > 0);
-
-	return err;
 }
 
 struct group_info {

include/mnl_utils.h

@@ -5,5 +5,7 @@
 struct mnl_socket *mnlu_socket_open(int bus);
 struct nlmsghdr *mnlu_msg_prepare(void *buf, uint32_t nlmsg_type, uint16_t flags,
 				  void *extra_header, size_t extra_header_size);
+int mnlu_socket_recv_run(struct mnl_socket *nl, unsigned int seq, void *buf, size_t buf_size,
+			 mnl_cb_t cb, void *data);
 
 #endif /* __MNL_UTILS_H__ */

lib/mnl_utils.c

@@ -3,11 +3,14 @@
  * mnl_utils.c	Helpers for working with libmnl.
  */
 
+#include <errno.h>
 #include <string.h>
 #include <time.h>
 #include <libmnl/libmnl.h>
 
+#include "libnetlink.h"
 #include "mnl_utils.h"
+#include "utils.h"
 
 struct mnl_socket *mnlu_socket_open(int bus)
 {
@@ -47,3 +50,61 @@ struct nlmsghdr *mnlu_msg_prepare(void *buf, uint32_t nlmsg_type, uint16_t flags
 
 	return nlh;
 }
+
+static int mnlu_cb_noop(const struct nlmsghdr *nlh, void *data)
+{
+	return MNL_CB_OK;
+}
+
+static int mnlu_cb_error(const struct nlmsghdr *nlh, void *data)
+{
+	const struct nlmsgerr *err = mnl_nlmsg_get_payload(nlh);
+
+	/* Netlink subsystems returns the errno value with different signess */
+	if (err->error < 0)
+		errno = -err->error;
+	else
+		errno = err->error;
+
+	if (nl_dump_ext_ack(nlh, NULL))
+		return MNL_CB_ERROR;
+
+	return err->error == 0 ? MNL_CB_STOP : MNL_CB_ERROR;
+}
+
+static int mnlu_cb_stop(const struct nlmsghdr *nlh, void *data)
+{
+	int len = *(int *)NLMSG_DATA(nlh);
+
+	if (len < 0) {
+		errno = -len;
+		nl_dump_ext_ack_done(nlh, len);
+		return MNL_CB_ERROR;
+	}
+	return MNL_CB_STOP;
+}
+
+static mnl_cb_t mnlu_cb_array[NLMSG_MIN_TYPE] = {
+	[NLMSG_NOOP]	= mnlu_cb_noop,
+	[NLMSG_ERROR]	= mnlu_cb_error,
+	[NLMSG_DONE]	= mnlu_cb_stop,
+	[NLMSG_OVERRUN]	= mnlu_cb_noop,
+};
+
+int mnlu_socket_recv_run(struct mnl_socket *nl, unsigned int seq, void *buf, size_t buf_size,
+			 mnl_cb_t cb, void *data)
+{
+	unsigned int portid = mnl_socket_get_portid(nl);
+	int err;
+
+	do {
+		err = mnl_socket_recvfrom(nl, buf, buf_size);
+		if (err <= 0)
+			break;
+		err = mnl_cb_run2(buf, err, seq, portid,
+				  cb, data, mnlu_cb_array,
+				  ARRAY_SIZE(mnlu_cb_array));
+	} while (err > 0);
+
+	return err;
+}