[PATCH iproute2-next v2] ipneigh: add support to print brief output of neigh cache in tabular format

Make use of the already available brief flag and print the basic details of
the IPv4 or IPv6 neighbour cache in a tabular format for better readability
when the brief output is expected.

$ ip -br neigh
172.16.12.100                           bridge0          b0:fc:36:2f:07:43
172.16.12.174                           bridge0          8c:16:45:2f:bc:1c
172.16.12.250                           bridge0          04:d9:f5:c1:0c:74
fe80::267b:9f70:745e:d54d               bridge0          b0:fc:36:2f:07:43
fd16:a115:6a62:0:8744:efa1:9933:2c4c    bridge0          8c:16:45:2f:bc:1c
fe80::6d9:f5ff:fec1:c74                 bridge0          04:d9:f5:c1:0c:74

And add "ip neigh show" to the list of ip sub commands mentioned in the man
page that support the brief output in tabular format.

Signed-off-by: Gokul Sivakumar <redacted>
---

Notes:
    Changes in v2:
    - Reordered the columns in the brief output to be consistent with the order of the
      fields in the non-brief output.
    - changed the format specifier width of dst field from "%-40s" to "%-39s " to be
      consistent with the way width of dev field is specified.

 ip/ipneigh.c  | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
 man/man8/ip.8 |  2 +-
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/ip/ipneigh.c b/ip/ipneigh.c
index 2d6b7f58..95bde520 100644
--- a/ip/ipneigh.c
+++ b/ip/ipneigh.c

@@ -251,6 +251,51 @@ static void print_neigh_state(unsigned int nud)
 	close_json_array(PRINT_JSON, NULL);
 }
 
+static int print_neigh_brief(FILE *fp, struct ndmsg *r, struct rtattr *tb[])
+{
+	if (tb[NDA_DST]) {
+		const char *dst;
+		int family = r->ndm_family;
+
+		if (family == AF_BRIDGE) {
+			if (RTA_PAYLOAD(tb[NDA_DST]) == sizeof(struct in6_addr))
+				family = AF_INET6;
+			else
+				family = AF_INET;
+		}
+
+		dst = format_host_rta(family, tb[NDA_DST]);
+		print_color_string(PRINT_ANY, ifa_family_color(family),
+				   "dst", "%-39s ", dst);
+	}
+
+	if (!filter.index && r->ndm_ifindex) {
+		print_color_string(PRINT_ANY, COLOR_IFNAME,
+				   "dev", "%-16s ",
+				   ll_index_to_name(r->ndm_ifindex));
+	}
+
+	if (tb[NDA_LLADDR]) {
+		const char *lladdr;
+
+		SPRINT_BUF(b1);
+
+		lladdr = ll_addr_n2a(RTA_DATA(tb[NDA_LLADDR]),
+				     RTA_PAYLOAD(tb[NDA_LLADDR]),
+				     ll_index_to_type(r->ndm_ifindex),
+				     b1, sizeof(b1));
+
+		print_color_string(PRINT_ANY, COLOR_MAC,
+				   "lladdr", "%s", lladdr);
+	}
+
+	print_string(PRINT_FP, NULL, "%s", "\n");
+	close_json_object();
+	fflush(fp);
+
+	return 0;
+}
+
 int print_neigh(struct nlmsghdr *n, void *arg)
 {
 	FILE *fp = (FILE *)arg;

@@ -337,6 +382,9 @@ int print_neigh(struct nlmsghdr *n, void *arg)
 	else if (n->nlmsg_type == RTM_GETNEIGH)
 		print_null(PRINT_ANY, "miss", "%s ", "miss");
 
+	if (brief)
+		return print_neigh_brief(fp, r, tb);
+
 	if (tb[NDA_DST]) {
 		const char *dst;
 		int family = r->ndm_family;

@@ -412,7 +460,7 @@ int print_neigh(struct nlmsghdr *n, void *arg)
 
 	print_string(PRINT_FP, NULL, "\n", "");
 	close_json_object();
-	fflush(stdout);
+	fflush(fp);
 
 	return 0;
 }

diff --git a/man/man8/ip.8 b/man/man8/ip.8
index c9f7671e..3f572889 100644
--- a/man/man8/ip.8
+++ b/man/man8/ip.8

@@ -227,7 +227,7 @@ print human readable rates in IEC units (e.g. 1Ki = 1024).
 .BR "\-br" , " \-brief"
 Print only basic information in a tabular format for better
 readability. This option is currently only supported by
-.BR "ip addr show " and " ip link show " commands.
+.BR "ip addr show ", " ip link show " & " ip neigh show " commands.
 
 .TP
 .BR "\-j", " \-json"

-- 
2.25.1

On 7/27/21 10:46 AM, Gokul Sivakumar wrote:

Make use of the already available brief flag and print the basic details of
the IPv4 or IPv6 neighbour cache in a tabular format for better readability
when the brief output is expected.

$ ip -br neigh
172.16.12.100                           bridge0          b0:fc:36:2f:07:43
172.16.12.174                           bridge0          8c:16:45:2f:bc:1c
172.16.12.250                           bridge0          04:d9:f5:c1:0c:74
fe80::267b:9f70:745e:d54d               bridge0          b0:fc:36:2f:07:43
fd16:a115:6a62:0:8744:efa1:9933:2c4c    bridge0          8c:16:45:2f:bc:1c
fe80::6d9:f5ff:fec1:c74                 bridge0          04:d9:f5:c1:0c:74

And add "ip neigh show" to the list of ip sub commands mentioned in the man
page that support the brief output in tabular format.

Signed-off-by: Gokul Sivakumar <redacted>
---

Notes:
    Changes in v2:
    - Reordered the columns in the brief output to be consistent with the order of the
      fields in the non-brief output.
    - changed the format specifier width of dst field from "%-40s" to "%-39s " to be
      consistent with the way width of dev field is specified.

 ip/ipneigh.c  | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
 man/man8/ip.8 |  2 +-
 2 files changed, 50 insertions(+), 2 deletions(-)

applied to iproute2-next