utils: Introduce and use print_name_and_link() to print name@link

There is at least three places implementing same things: two in
ipaddress.c print_linkinfo() & print_linkinfo_brief() and one in
bridge/link.c.

They are diverge from each other very little: bridge/link.c does not
support JSON output at the moment and print_linkinfo_brief() does not
handle IFLA_LINK_NETNS case.

Introduce and use print_name_and_link() routine to handle name@link
output in all possible variations; respect IFLA_LINK_NETNS attribute to
handle case when link is in different namespace; use ll_idx_n2a() for
interface name instead of "<nil>" to share logic with other code (e.g.
ll_name_to_index() and ll_index_to_name()) supporting such template.

Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>

bridge/link.c

@@ -125,20 +125,13 @@ int print_linkinfo(const struct sockaddr_nl *who,
 	if (n->nlmsg_type == RTM_DELLINK)
 		fprintf(fp, "Deleted ");
 
-	fprintf(fp, "%d: %s ", ifi->ifi_index,
+	fprintf(fp, "%d: ", ifi->ifi_index);
-		tb[IFLA_IFNAME] ? rta_getattr_str(tb[IFLA_IFNAME]) : "<nil>");
+
+	print_name_and_link("%s: ", COLOR_NONE, name, tb);
 
 	if (tb[IFLA_OPERSTATE])
 		print_operstate(fp, rta_getattr_u8(tb[IFLA_OPERSTATE]));
 
-	if (tb[IFLA_LINK]) {
-		int iflink = rta_getattr_u32(tb[IFLA_LINK]);
-
-		fprintf(fp, "@%s: ",
-			iflink ? ll_index_to_name(iflink) : "NONE");
-	} else
-		fprintf(fp, ": ");
-
 	print_link_flags(fp, ifi->ifi_flags);
 
 	if (tb[IFLA_MTU])

include/utils.h

@@ -12,6 +12,7 @@
 #include "libnetlink.h"
 #include "ll_map.h"
 #include "rtm_map.h"
+#include "json_print.h"
 
 extern int preferred_family;
 extern int human_readable;
@@ -250,6 +251,9 @@ void print_escape_buf(const __u8 *buf, size_t len, const char *escape);
 int print_timestamp(FILE *fp);
 void print_nlmsg_timestamp(FILE *fp, const struct nlmsghdr *n);
 
+unsigned int print_name_and_link(const char *fmt, enum color_attr color,
+				 const char *name, struct rtattr *tb[]);
+
 #define BIT(nr)                 (1UL << (nr))
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

ip/ipaddress.c

@@ -760,7 +760,6 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
 	struct rtattr *tb[IFLA_MAX+1];
 	int len = n->nlmsg_len;
 	const char *name;
-	char buf[32] = { 0, };
 	unsigned int m_flag = 0;
 
 	if (n->nlmsg_type != RTM_NEWLINK && n->nlmsg_type != RTM_DELLINK)
@@ -810,25 +809,7 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
 	if (n->nlmsg_type == RTM_DELLINK)
 		print_bool(PRINT_ANY, "deleted", "Deleted ", true);
 
-	if (tb[IFLA_LINK]) {
+	m_flag = print_name_and_link("%-16s ", COLOR_NONE, name, tb);
-		int iflink = rta_getattr_u32(tb[IFLA_LINK]);
-
-		if (iflink == 0) {
-			snprintf(buf, sizeof(buf), "%s@NONE", name);
-			print_null(PRINT_JSON, "link", NULL, NULL);
-		} else {
-			const char *link = ll_index_to_name(iflink);
-
-			print_string(PRINT_JSON, "link", NULL, link);
-			snprintf(buf, sizeof(buf), "%s@%s", name, link);
-			m_flag = ll_index_to_flags(iflink);
-			m_flag = !(m_flag & IFF_UP);
-		}
-	} else
-		snprintf(buf, sizeof(buf), "%s", name);
-
-	print_string(PRINT_FP, NULL, "%-16s ", buf);
-	print_string(PRINT_JSON, "ifname", NULL, name);
 
 	if (tb[IFLA_OPERSTATE])
 		print_operstate(fp, rta_getattr_u8(tb[IFLA_OPERSTATE]));
@@ -936,29 +917,8 @@ int print_linkinfo(const struct sockaddr_nl *who,
 		print_bool(PRINT_ANY, "deleted", "Deleted ", true);
 
 	print_int(PRINT_ANY, "ifindex", "%d: ", ifi->ifi_index);
-	print_color_string(PRINT_ANY, COLOR_IFNAME, "ifname", "%s", name);
 
-	if (tb[IFLA_LINK]) {
+	m_flag = print_name_and_link("%s: ", COLOR_IFNAME, name, tb);
-		int iflink = rta_getattr_u32(tb[IFLA_LINK]);
-
-		if (iflink == 0)
-			print_null(PRINT_ANY, "link", "@%s: ", "NONE");
-		else {
-			if (tb[IFLA_LINK_NETNSID])
-				print_int(PRINT_ANY,
-					  "link_index", "@if%d: ", iflink);
-			else {
-				print_string(PRINT_ANY,
-					     "link",
-					     "@%s: ",
-					     ll_index_to_name(iflink));
-				m_flag = ll_index_to_flags(iflink);
-				m_flag = !(m_flag & IFF_UP);
-			}
-		}
-	} else {
-		print_string(PRINT_FP, NULL, ": ", NULL);
-	}
 	print_link_flags(fp, ifi->ifi_flags, m_flag);
 
 	if (tb[IFLA_MTU])

lib/utils.c

@@ -33,6 +33,7 @@
 
 #include "rt_names.h"
 #include "utils.h"
+#include "ll_map.h"
 #include "namespace.h"
 
 int resolve_hosts;
@@ -1261,6 +1262,54 @@ int print_timestamp(FILE *fp)
 	return 0;
 }
 
+unsigned int print_name_and_link(const char *fmt, enum color_attr color,
+				 const char *name, struct rtattr *tb[])
+{
+	const char *link = NULL;
+	unsigned int m_flag = 0;
+	SPRINT_BUF(b1);
+
+	if (tb[IFLA_LINK]) {
+		int iflink = rta_getattr_u32(tb[IFLA_LINK]);
+
+		if (iflink) {
+			if (tb[IFLA_LINK_NETNSID]) {
+				if (is_json_context()) {
+					print_int(PRINT_JSON,
+						  "link_index", NULL, iflink);
+				} else {
+					link = ll_idx_n2a(iflink);
+				}
+			} else {
+				link = ll_index_to_name(iflink);
+
+				if (is_json_context()) {
+					print_string(PRINT_JSON,
+						     "link", NULL, link);
+					link = NULL;
+				}
+
+				m_flag = ll_index_to_flags(iflink);
+				m_flag = !(m_flag & IFF_UP);
+			}
+		} else {
+			if (is_json_context())
+				print_null(PRINT_JSON, "link", NULL, NULL);
+			else
+				link = "NONE";
+		}
+
+		if (link) {
+			snprintf(b1, sizeof(b1), "%s@%s", name, link);
+			name = b1;
+		}
+	}
+
+	print_color_string(PRINT_ANY, color, "ifname", fmt, name);
+
+	return m_flag;
+}
+
 int cmdlineno;
 
 /* Like glibc getline but handle continuation lines and comments */