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

This little dance of mnl_socket_open(), option setting, and bind, is the
same regardless of tool. Extract into a new module that should hold helpers
for working with libmnl, mnl_util.c.

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

devlink/Makefile

@@ -12,7 +12,7 @@ endif
 
 all: $(TARGETS) $(LIBS)
 
-devlink: $(DEVLINKOBJ)
+devlink: $(DEVLINKOBJ) $(LIBNETLINK)
 	$(QUIET_LINK)$(CC) $^ $(LDFLAGS) $(LDLIBS) -o $@
 
 install: all

devlink/mnlg.c

@@ -19,6 +19,7 @@
 #include <linux/genetlink.h>
 
 #include "libnetlink.h"
+#include "mnl_utils.h"
 #include "utils.h"
 #include "mnlg.h"
 
@@ -263,7 +264,6 @@ struct mnlg_socket *mnlg_socket_open(const char *family_name, uint8_t version)
 {
 	struct mnlg_socket *nlg;
 	struct nlmsghdr *nlh;
-	int one = 1;
 	int err;
 
 	nlg = malloc(sizeof(*nlg));
@@ -274,19 +274,9 @@ struct mnlg_socket *mnlg_socket_open(const char *family_name, uint8_t version)
 	if (!nlg->buf)
 		goto err_buf_alloc;
 
-	nlg->nl = mnl_socket_open(NETLINK_GENERIC);
+	nlg->nl = mnlu_socket_open(NETLINK_GENERIC);
 	if (!nlg->nl)
-		goto err_mnl_socket_open;
+		goto err_socket_open;
-
-	/* Older kernels may no support capped/extended ACK reporting */
-	mnl_socket_setsockopt(nlg->nl, NETLINK_CAP_ACK, &one, sizeof(one));
-	mnl_socket_setsockopt(nlg->nl, NETLINK_EXT_ACK, &one, sizeof(one));
-
-	err = mnl_socket_bind(nlg->nl, 0, MNL_SOCKET_AUTOPID);
-	if (err < 0)
-		goto err_mnl_socket_bind;
-
-	nlg->portid = mnl_socket_get_portid(nlg->nl);
 
 	nlh = __mnlg_msg_prepare(nlg, CTRL_CMD_GETFAMILY,
 				 NLM_F_REQUEST | NLM_F_ACK, GENL_ID_CTRL, 1);
@@ -305,9 +295,8 @@ struct mnlg_socket *mnlg_socket_open(const char *family_name, uint8_t version)
 
 err_mnlg_socket_recv_run:
 err_mnlg_socket_send:
-err_mnl_socket_bind:
 	mnl_socket_close(nlg->nl);
-err_mnl_socket_open:
+err_socket_open:
 	free(nlg->buf);
 err_buf_alloc:
 	free(nlg);

include/mnl_utils.h

@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __MNL_UTILS_H__
+#define __MNL_UTILS_H__ 1
+
+struct mnl_socket *mnlu_socket_open(int bus);
+
+#endif /* __MNL_UTILS_H__ */

lib/Makefile

@@ -7,7 +7,7 @@ UTILOBJ = utils.o rt_names.o ll_map.o ll_types.o ll_proto.o ll_addr.o \
 	inet_proto.o namespace.o json_writer.o json_print.o \
 	names.o color.o bpf.o exec.o fs.o cg_map.o
 
-NLOBJ=libgenl.o libnetlink.o
+NLOBJ=libgenl.o libnetlink.o mnl_utils.o
 
 all: libnetlink.a libutil.a
 

lib/mnl_utils.c

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * mnl_utils.c	Helpers for working with libmnl.
+ */
+
+#include <libmnl/libmnl.h>
+
+#include "mnl_utils.h"
+
+struct mnl_socket *mnlu_socket_open(int bus)
+{
+	struct mnl_socket *nl;
+	int one = 1;
+
+	nl = mnl_socket_open(bus);
+	if (nl == NULL)
+		return NULL;
+
+	mnl_socket_setsockopt(nl, NETLINK_CAP_ACK, &one, sizeof(one));
+	mnl_socket_setsockopt(nl, NETLINK_EXT_ACK, &one, sizeof(one));
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0)
+		goto err_bind;
+
+	return nl;
+
+err_bind:
+	mnl_socket_close(nl);
+	return NULL;
+}