netdev - [PATCH iproute2-next v2] ss: Add support for dumping TCP bound-inactive sockets.

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Date: Tue, 19 Dec 2023 14:18:13 +0100
From: Guillaume Nault <gnault@...hat.com>
To: David Ahern <dsahern@...il.com>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Michal Kubecek <mkubecek@...e.cz>
Subject: [PATCH iproute2-next v2] ss: Add support for dumping TCP
 bound-inactive sockets.

Make ss aware of the new "bound-inactive" pseudo-state for TCP (see
Linux commit 91051f003948 ("tcp: Dump bound-only sockets in inet_diag.")).
These are TCP sockets that have been bound, but are neither listening nor
connecting.

With this patch, these sockets can now be dumped with:

  * the existing -a (--all) option, to dump all sockets, including
    bound-inactive ones,

  * the new -B (--bound-inactive) option, to dump them exclusively,

  * the new "bound-inactive" state, to be used in a STATE-FILTER.

Note that the SS_BOUND_INACTIVE state is a pseudo-state used for queries
only. The kernel returns them as SS_CLOSE.

The SS_NEW_SYN_RECV pseudo-state is added in this patch only because we
have to set its entry in the sstate_namel array (in scan_state()). Care
is taken not to make it visible by users.

Signed-off-by: Guillaume Nault <gnault@...hat.com>
---
v2: Reject the "new-syn-recv" pseudo-state in scan_state() and add
    comments to make it clear that NEW_SYN_RECV is kernel-only and
    and shouldn't be exposed to users (Kuniyuki Iwashima).

 man/man8/ss.8 |  7 +++++++
 misc/ss.c     | 20 +++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/man/man8/ss.8 b/man/man8/ss.8
index 073e9f03..4ece41fa 100644
--- a/man/man8/ss.8
+++ b/man/man8/ss.8
@@ -40,6 +40,10 @@ established connections) sockets.
 .B \-l, \-\-listening
 Display only listening sockets (these are omitted by default).
 .TP
+.B \-B, \-\-bound-inactive
+Display only TCP bound but inactive (not listening, connecting, etc.) sockets
+(these are omitted by default).
+.TP
 .B \-o, \-\-options
 Show timer information. For TCP protocol, the output format is:
 .RS
@@ -456,6 +460,9 @@ states except for
 - opposite to
 .B bucket
 
+.B bound-inactive
+- bound but otherwise inactive sockets (not listening, connecting, etc.)
+
 .SH EXPRESSION
 
 .B EXPRESSION
diff --git a/misc/ss.c b/misc/ss.c
index 16ffb6c8..c220a075 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -210,6 +210,8 @@ enum {
 	SS_LAST_ACK,
 	SS_LISTEN,
 	SS_CLOSING,
+	SS_NEW_SYN_RECV, /* Kernel only value, not for use in user space */
+	SS_BOUND_INACTIVE,
 	SS_MAX
 };
 
@@ -1382,6 +1384,8 @@ static void sock_state_print(struct sockstat *s)
 		[SS_LAST_ACK] = "LAST-ACK",
 		[SS_LISTEN] =	"LISTEN",
 		[SS_CLOSING] = "CLOSING",
+		[SS_NEW_SYN_RECV] = "UNDEF", /* Never returned by kernel */
+		[SS_BOUND_INACTIVE] = "UNDEF", /* Never returned by kernel */
 	};
 
 	switch (s->local.family) {
@@ -5339,6 +5343,7 @@ static void _usage(FILE *dest)
 "   -r, --resolve       resolve host names\n"
 "   -a, --all           display all sockets\n"
 "   -l, --listening     display listening sockets\n"
+"   -B, --bound-inactive display TCP bound but inactive sockets\n"
 "   -o, --options       show timer information\n"
 "   -e, --extended      show detailed socket information\n"
 "   -m, --memory        show socket memory usage\n"
@@ -5421,9 +5426,17 @@ static int scan_state(const char *state)
 		[SS_LAST_ACK] = "last-ack",
 		[SS_LISTEN] =	"listening",
 		[SS_CLOSING] = "closing",
+		[SS_NEW_SYN_RECV] = "new-syn-recv",
+		[SS_BOUND_INACTIVE] = "bound-inactive",
 	};
 	int i;
 
+	/* NEW_SYN_RECV is a kernel implementation detail. It shouldn't be used
+	 * or even be visible by users.
+	 */
+	if (strcasecmp(state, "new-syn-recv") == 0)
+		goto wrong_state;
+
 	if (strcasecmp(state, "close") == 0 ||
 	    strcasecmp(state, "closed") == 0)
 		return (1<<SS_CLOSE);
@@ -5446,6 +5459,7 @@ static int scan_state(const char *state)
 			return (1<<i);
 	}
 
+wrong_state:
 	fprintf(stderr, "ss: wrong state name: %s\n", state);
 	exit(-1);
 }
@@ -5487,6 +5501,7 @@ static const struct option long_opts[] = {
 	{ "vsock", 0, 0, OPT_VSOCK },
 	{ "all", 0, 0, 'a' },
 	{ "listening", 0, 0, 'l' },
+	{ "bound-inactive", 0, 0, 'B' },
 	{ "ipv4", 0, 0, '4' },
 	{ "ipv6", 0, 0, '6' },
 	{ "packet", 0, 0, '0' },
@@ -5525,7 +5540,7 @@ int main(int argc, char *argv[])
 	int state_filter = 0;
 
 	while ((ch = getopt_long(argc, argv,
-				 "dhaletuwxnro460spTbEf:mMiA:D:F:vVzZN:KHSO",
+				 "dhalBetuwxnro460spTbEf:mMiA:D:F:vVzZN:KHSO",
 				 long_opts, NULL)) != EOF) {
 		switch (ch) {
 		case 'n':
@@ -5590,6 +5605,9 @@ int main(int argc, char *argv[])
 		case 'l':
 			state_filter = (1 << SS_LISTEN) | (1 << SS_CLOSE);
 			break;
+		case 'B':
+			state_filter = 1 << SS_BOUND_INACTIVE;
+			break;
 		case '4':
 			filter_af_set(&current_filter, AF_INET);
 			break;
-- 
2.39.2