[iproute PATCH v4 2/2] ss: support closing inet sockets via SOCK_DESTROY.

Lorenzo Colitti
2016-01-08T08:32:52Z

This patch adds a -K / --kill option to ss that attempts to
forcibly close matching sockets using SOCK_DESTROY.

Because ss typically prints sockets instead of acting on them,
and because the kernel only supports forcibly closing some types
of sockets, the output of -K is as follows:

- If closing the socket succeeds, the socket is printed.
- If the kernel does not support forcibly closing this type of
socket (e.g., if it's a UDP socket, or a TIME_WAIT socket),
the socket is silently skipped.
- If an error occurs (e.g., permission denied), the error is
reported and ss exits.

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
---
include/linux/sock_diag.h | 1 +
man/man8/ss.8 | 5 +++++
misc/ss.c | 50 +++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index 024e1f4..dafcb89 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h
@@ -4,6 +4,7 @@
#include <linux/types.h>

#define SOCK_DIAG_BY_FAMILY 20
+#define SOCK_DESTROY 21

struct sock_diag_req {
__u8 sdiag_family;
diff --git a/man/man8/ss.8 b/man/man8/ss.8
index f4d5264..758460c 100644
--- a/man/man8/ss.8
+++ b/man/man8/ss.8
@@ -48,6 +48,11 @@ Show process using socket.
.B \-i, \-\-info
Show internal TCP information.
.TP
+.B \-K, \-\-kill
+Attempts to forcibly close sockets. This option displays sockets that are
+successfully closed and silently skips sockets that the kernel does not support
+closing. It supports IPv4 and IPv6 sockets only.
+.TP
.B \-s, \-\-summary
Print summary statistics. This option does not parse socket lists obtaining
summary from various sources. It is useful when amount of sockets is so huge
diff --git a/misc/ss.c b/misc/ss.c
index 0dab32c..13fcc8f 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -160,6 +160,7 @@ struct filter
int states;
int families;
struct ssfilter *f;
+ bool kill;
};

static const struct filter default_dbs[MAX_DB] = {
@@ -2194,8 +2195,27 @@ static int sockdiag_send(int family, int fd, int protocol, struct filter *f)
struct inet_diag_arg {
struct filter *f;
int protocol;
+ struct rtnl_handle *rth;
};

+static int kill_inet_sock(const struct sockaddr_nl *addr,
+ struct nlmsghdr *h, void *arg)
+{
+ struct inet_diag_msg *d = NLMSG_DATA(h);
+ struct inet_diag_arg *diag_arg = arg;
+ struct rtnl_handle *rth = diag_arg->rth;
+ DIAG_REQUEST(req, struct inet_diag_req_v2 r);
+
+ req.nlh.nlmsg_type = SOCK_DESTROY;
+ req.nlh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+ req.nlh.nlmsg_seq = ++rth->seq;
+ req.r.sdiag_family = d->idiag_family;
+ req.r.sdiag_protocol = diag_arg->protocol;
+ req.r.id = d->id;
+
+ return rtnl_talk(rth, &req.nlh, NULL, 0);
+}
+
static int show_one_inet_sock(const struct sockaddr_nl *addr,
struct nlmsghdr *h, void *arg)
{
@@ -2205,6 +2225,15 @@ static int show_one_inet_sock(const struct sockaddr_nl *addr,

if (!(diag_arg->f->families & (1 << r->idiag_family)))
return 0;
+ if (diag_arg->f->kill && kill_inet_sock(addr, h, arg) != 0) {
+ if (errno == EOPNOTSUPP || errno == ENOENT) {
+ /* Socket can't be closed, or is already closed. */
+ return 0;
+ } else {
+ perror("SOCK_DESTROY answers");
+ return -1;
+ }
+ }
if ((err = inet_show_sock(h, diag_arg->f, diag_arg->protocol)) < 0)
return err;

@@ -2214,12 +2243,21 @@ static int show_one_inet_sock(const struct sockaddr_nl *addr,
static int inet_show_netlink(struct filter *f, FILE *dump_fp, int protocol)
{
int err = 0;
- struct rtnl_handle rth;
+ struct rtnl_handle rth, rth2;
int family = PF_INET;
struct inet_diag_arg arg = { .f = f, .protocol = protocol };

if (rtnl_open_byproto(&rth, 0, NETLINK_SOCK_DIAG))
return -1;
+
+ if (f->kill) {
+ if (rtnl_open_byproto(&rth2, 0, NETLINK_SOCK_DIAG)) {
+ rtnl_close(&rth);
+ return -1;
+ }
+ arg.rth = &rth2;
+ }
+
rth.dump = MAGIC_SEQ;
rth.dump_fp = dump_fp;
if (preferred_family == PF_INET6)
@@ -2243,6 +2281,8 @@ again:

Exit:
rtnl_close(&rth);
+ if (arg.rth)
+ rtnl_close(arg.rth);
return err;
}

@@ -3489,6 +3529,8 @@ static void _usage(FILE *dest)
" -x, --unix display only Unix domain sockets\n"
" -f, --family=FAMILY display sockets of type FAMILY\n"
"\n"
+" -K, --kill forcibly close sockets, display what was closed\n"
+"\n"
" -A, --query=QUERY, --socket=QUERY\n"
" QUERY := {all|inet|tcp|udp|raw|unix|unix_dgram|unix_stream|unix_seqpacket|packet|netlink}[,QUERY]\n"
"\n"
@@ -3579,6 +3621,7 @@ static const struct option long_opts[] = {
{ "context", 0, 0, 'Z' },
{ "contexts", 0, 0, 'z' },
{ "net", 1, 0, 'N' },
+ { "kill", 0, 0, 'K' },
{ 0 }

};
@@ -3593,7 +3636,7 @@ int main(int argc, char *argv[])
int ch;
int state_filter = 0;

- while ((ch = getopt_long(argc, argv, "dhaletuwxnro460spbEf:miA:D:F:vVzZN:",
+ while ((ch = getopt_long(argc, argv, "dhaletuwxnro460spbEf:miA:D:F:vVzZN:K",
long_opts, NULL)) != EOF) {
switch(ch) {
case 'n':
@@ -3774,6 +3817,9 @@ int main(int argc, char *argv[])
if (netns_switch(optarg))
exit(1);
break;
+ case 'K':
+ current_filter.kill = 1;
+ break;
case 'h':
help();
case '?':
--
2.6.0.rc2.230.g3dd15c0