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Date: Thu, 6 Apr 2023 10:15:41 +1000
From: David Gibson <david@gibson.dropbear.id.au>
To: Stefano Brivio <sbrivio@redhat.com>
Subject: Re: [PATCH 06/14] nstool: Detect what namespaces target is in
Message-ID: <ZC4PLXjm7/SxmKr9@yekko>
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On Wed, Apr 05, 2023 at 01:58:25PM +0200, Stefano Brivio wrote:
> On Tue, 4 Apr 2023 11:46:30 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
>=20
> > Give nstool the ability to detect what namespaces the target process is=
in,
> > relative to where it's called. That is, those namespace types for which
> > the target is not in the same namespace as the caller. For now, just
> > print this information with "info", which can be useful for debugging.
> >=20
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> > test/nstool.c | 154 +++++++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 140 insertions(+), 14 deletions(-)
> >=20
> > diff --git a/test/nstool.c b/test/nstool.c
> > index 2cb4fb3..428c9c4 100644
> > --- a/test/nstool.c
> > +++ b/test/nstool.c
> > @@ -15,8 +15,13 @@
> > #include <errno.h>
> > #include <unistd.h>
> > #include <getopt.h>
> > +#include <stdarg.h>
> > #include <sys/socket.h>
> > #include <linux/un.h>
> > +#include <linux/limits.h>
> > +#include <sched.h>
> > +
> > +#define ARRAY_SIZE(a) ((int)(sizeof(a) / sizeof((a)[0])))
> > =20
> > #define die(...) \
> > do { \
> > @@ -24,6 +29,28 @@
> > exit(1); \
> > } while (0)
> > =20
> > +struct ns_type {
> > + int flag;
> > + const char *name;
> > +};
> > +
> > +const struct ns_type nstypes[] =3D {
> > + { CLONE_NEWCGROUP, "cgroup" },
> > + { CLONE_NEWIPC, "ipc" },
> > + { CLONE_NEWNET, "net" },
> > + { CLONE_NEWNS, "mnt" },
> > + { CLONE_NEWPID, "pid" },
> > + { CLONE_NEWTIME, "time" },
> > + { CLONE_NEWUSER, "user" },
> > + { CLONE_NEWUTS, "uts" },
> > +};
> > +
> > +struct holder_info {
> > + pid_t pid;
> > + uid_t uid;
> > + gid_t gid;
> > +};
> > +
> > static void usage(void)
> > {
> > die("Usage:\n"
> > @@ -41,12 +68,16 @@ static void usage(void)
> > " terminate.\n");
> > }
> > =20
> > -static int connect_ctl(const char * sockpath, bool wait)
> > +static int connect_ctl(const char *sockpath, bool wait,
> > + struct holder_info *info,
> > + struct ucred *peercred)
> > {
> > int fd =3D socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
> > struct sockaddr_un addr =3D {
> > .sun_family =3D AF_UNIX,
> > };
> > + struct holder_info discard;
> > + ssize_t len;
> > int rc;
> > =20
> > if (fd < 0)
> > @@ -61,6 +92,25 @@ static int connect_ctl(const char * sockpath, bool w=
ait)
> > die("connect() to %s: %s\n", sockpath, strerror(errno));
> > } while (rc < 0);
> > =20
> > + if (!info)
> > + info =3D &discard;
>=20
> As you close the socket anyway moments later, I wonder if it wouldn't
> be doable (and more natural) to just do:
>=20
> if (info) {
> len =3D read(fd, info, sizeof(*info));
> ...
> }
I had something like that initially, but that causes the holder to
spit a broken pipe error, which is distracting.
> if (peercred) {
> ...
> }
>=20
> ...but maybe it adds unnecessary complication to 7/14 (or perhaps the
> magic is not really part of 'info'?).
>=20
--=20
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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