DCCP support was retired in kernel commit 2a63dd0edf38 ("net: Retire
DCCP socket."). However, ss still attempts to query DCCP sockets via
netlink, which triggers repeated SELinux warnings in dmesg:

  SELinux: unrecognized netlink message: protocol=4 nlmsg_type=19 \
    sclass=netlink_tcpdiag_socket pid=188945 comm=ss

Stop sending DCCPDIAG_GETSOCK netlink messages to suppress these
warnings and align ss with the kernel change.

After this commit, running `ss -d` fails with:

  # ./misc/ss -d
  ./misc/ss: invalid option -- 'd'
  [...]

  # ./misc/ss --dccp
  ./misc/ss: unrecognized option '--dccp'
  [...]

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
---
 man/man8/ss.8 |  5 +----
 misc/ss.c     | 41 ++++++-----------------------------------
 2 files changed, 7 insertions(+), 39 deletions(-)

diff --git a/man/man8/ss.8 b/man/man8/ss.8
index 70e0a566..3871612d 100644
--- a/man/man8/ss.8
+++ b/man/man8/ss.8
@@ -377,9 +377,6 @@ Display TCP sockets.
 .B \-u, \-\-udp
 Display UDP sockets.
 .TP
-.B \-d, \-\-dccp
-Display DCCP sockets.
-.TP
 .B \-w, \-\-raw
 Display RAW sockets.
 .TP
@@ -411,7 +408,7 @@ supported: unix, inet, inet6, link, netlink, vsock, tipc, xdp.
 .B \-A QUERY, \-\-query=QUERY, \-\-socket=QUERY
 List of socket tables to dump, separated by commas. The following identifiers
 are understood: all, inet, tcp, udp, raw, unix, packet, netlink, unix_dgram,
-unix_stream, unix_seqpacket, packet_raw, packet_dgram, dccp, sctp, tipc,
+unix_stream, unix_seqpacket, packet_raw, packet_dgram, sctp, tipc,
 vsock_stream, vsock_dgram, xdp, mptcp. Any item in the list may optionally be
 prefixed by an exclamation mark
 .RB ( ! )
diff --git a/misc/ss.c b/misc/ss.c
index 14e9f27a..b5f59a37 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -195,7 +195,6 @@ static const char *dg_proto;
 enum {
 	TCP_DB,
 	MPTCP_DB,
-	DCCP_DB,
 	UDP_DB,
 	RAW_DB,
 	UNIX_DG_DB,
@@ -215,7 +214,7 @@ enum {
 #define PACKET_DBM ((1<<PACKET_DG_DB)|(1<<PACKET_R_DB))
 #define UNIX_DBM ((1<<UNIX_DG_DB)|(1<<UNIX_ST_DB)|(1<<UNIX_SQ_DB))
 #define ALL_DB ((1<<MAX_DB)-1)
-#define INET_L4_DBM ((1<<TCP_DB)|(1<<MPTCP_DB)|(1<<UDP_DB)|(1<<DCCP_DB)|(1<<SCTP_DB))
+#define INET_L4_DBM ((1<<TCP_DB)|(1<<MPTCP_DB)|(1<<UDP_DB)|(1<<SCTP_DB))
 #define INET_DBM (INET_L4_DBM | (1<<RAW_DB))
 #define VSOCK_DBM ((1<<VSOCK_ST_DB)|(1<<VSOCK_DG_DB))
 
@@ -274,10 +273,6 @@ static const struct filter default_dbs[MAX_DB] = {
 		.states   = SS_CONN,
 		.families = FAMILY_MASK(AF_INET) | FAMILY_MASK(AF_INET6),
 	},
-	[DCCP_DB] = {
-		.states   = SS_CONN,
-		.families = FAMILY_MASK(AF_INET) | FAMILY_MASK(AF_INET6),
-	},
 	[UDP_DB] = {
 		.states   = (1 << SS_ESTABLISHED),
 		.families = FAMILY_MASK(AF_INET) | FAMILY_MASK(AF_INET6),
@@ -388,13 +383,12 @@ static int filter_db_parse(struct filter *f, const char *s)
 		int dbs[MAX_DB + 1];
 	} db_name_tbl[] = {
 #define ENTRY(name, ...) { #name, { __VA_ARGS__, MAX_DB } }
-		ENTRY(all, UDP_DB, DCCP_DB, TCP_DB, MPTCP_DB, RAW_DB,
+		ENTRY(all, UDP_DB, TCP_DB, MPTCP_DB, RAW_DB,
 			   UNIX_ST_DB, UNIX_DG_DB, UNIX_SQ_DB,
 			   PACKET_R_DB, PACKET_DG_DB, NETLINK_DB,
 			   SCTP_DB, VSOCK_ST_DB, VSOCK_DG_DB, XDP_DB),
-		ENTRY(inet, UDP_DB, DCCP_DB, TCP_DB, MPTCP_DB, SCTP_DB, RAW_DB),
+		ENTRY(inet, UDP_DB, TCP_DB, MPTCP_DB, SCTP_DB, RAW_DB),
 		ENTRY(udp, UDP_DB),
-		ENTRY(dccp, DCCP_DB),
 		ENTRY(tcp, TCP_DB),
 		ENTRY(mptcp, MPTCP_DB),
 		ENTRY(sctp, SCTP_DB),
@@ -935,8 +929,6 @@ static const char *proto_name(int protocol)
 		return "mptcp";
 	case IPPROTO_SCTP:
 		return "sctp";
-	case IPPROTO_DCCP:
-		return "dccp";
 	case IPPROTO_ICMPV6:
 		return "icmp6";
 	}
@@ -3897,8 +3889,6 @@ static int tcpdiag_send(int fd, int protocol, struct filter *f)
 
 	if (protocol == IPPROTO_TCP)
 		req.nlh.nlmsg_type = TCPDIAG_GETSOCK;
-	else if (protocol == IPPROTO_DCCP)
-		req.nlh.nlmsg_type = DCCPDIAG_GETSOCK;
 	else
 		return -1;
 
@@ -4134,7 +4124,7 @@ static int inet_show_netlink(struct filter *f, FILE *dump_fp, int protocol)
 
 	/* Suppress netlink errors. Older kernels do not support extended
 	 * protocol requests using INET_DIAG_REQ_PROTOCOL, and some protocols
-	 * may not be available in the running kernel (e.g. SCTP, DCCP).
+	 * may not be available in the running kernel (e.g. SCTP).
 	 * In both cases the kernel returns EINVAL which would cause
 	 * rtnl_dump_error() to print a confusing "RTNETLINK answers" error.
 	 */
@@ -4309,18 +4299,6 @@ static int mptcp_show(struct filter *f)
 	return 0;
 }
 
-static int dccp_show(struct filter *f)
-{
-	if (!filter_af_get(f, AF_INET) && !filter_af_get(f, AF_INET6))
-		return 0;
-
-	if (!getenv("PROC_NET_DCCP") && !getenv("PROC_ROOT")
-	    && inet_show_netlink(f, NULL, IPPROTO_DCCP) == 0)
-		return 0;
-
-	return 0;
-}
-
 static int sctp_show(struct filter *f)
 {
 	if (!filter_af_get(f, AF_INET) && !filter_af_get(f, AF_INET6))
@@ -5779,7 +5757,6 @@ static void _usage(FILE *dest)
 "   -M, --mptcp         display only MPTCP sockets\n"
 "   -S, --sctp          display only SCTP sockets\n"
 "   -u, --udp           display only UDP sockets\n"
-"   -d, --dccp          display only DCCP sockets\n"
 "   -w, --raw           display only RAW sockets\n"
 "   -x, --unix          display only Unix domain sockets\n"
 "       --tipc          display only TIPC sockets\n"
@@ -5795,7 +5772,7 @@ static void _usage(FILE *dest)
 "       --inet-sockopt  show various inet socket options\n"
 "\n"
 "   -A, --query=QUERY, --socket=QUERY\n"
-"       QUERY := {all|inet|tcp|mptcp|udp|raw|unix|unix_dgram|unix_stream|unix_seqpacket|packet|packet_raw|packet_dgram|netlink|dccp|sctp|vsock_stream|vsock_dgram|tipc|xdp}[,QUERY]\n"
+"       QUERY := {all|inet|tcp|mptcp|udp|raw|unix|unix_dgram|unix_stream|unix_seqpacket|packet|packet_raw|packet_dgram|netlink|sctp|vsock_stream|vsock_dgram|tipc|xdp}[,QUERY]\n"
 "\n"
 "   -D, --diag=FILE     Dump raw information about TCP sockets to FILE\n"
 "   -F, --filter=FILE   read filter information from FILE\n"
@@ -5907,7 +5884,6 @@ static const struct option long_opts[] = {
 	{ "threads", 0, 0, 'T' },
 	{ "bpf", 0, 0, 'b' },
 	{ "events", 0, 0, 'E' },
-	{ "dccp", 0, 0, 'd' },
 	{ "tcp", 0, 0, 't' },
 	{ "sctp", 0, 0, 'S' },
 	{ "udp", 0, 0, 'u' },
@@ -5961,7 +5937,7 @@ int main(int argc, char *argv[])
 	int state_filter = 0;
 
 	while ((ch = getopt_long(argc, argv,
-				 "dhalBetuwxnro460spTbEf:mMiA:D:F:vVzZN:KHQSO",
+				 "halBetuwxnro460spTbEf:mMiA:D:F:vVzZN:KHQSO",
 				 long_opts, NULL)) != EOF) {
 		switch (ch) {
 		case 'n':
@@ -5996,9 +5972,6 @@ int main(int argc, char *argv[])
 		case 'E':
 			follow_events = 1;
 			break;
-		case 'd':
-			filter_db_set(&current_filter, DCCP_DB, true);
-			break;
 		case 't':
 			filter_db_set(&current_filter, TCP_DB, true);
 			break;
@@ -6290,8 +6263,6 @@ int main(int argc, char *argv[])
 		udp_show(&current_filter);
 	if (current_filter.dbs & (1<<TCP_DB))
 		tcp_show(&current_filter);
-	if (current_filter.dbs & (1<<DCCP_DB))
-		dccp_show(&current_filter);
 	if (current_filter.dbs & (1<<SCTP_DB))
 		sctp_show(&current_filter);
 	if (current_filter.dbs & VSOCK_DBM)
-- 
2.52.0