Re: [PATCH] conntrackd: make conntrackd namespace aware

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi Ansis,

On Fri, Aug 31, 2012 at 06:11:55PM -0700, Ansis Atteka wrote:
> This patch allows conntrackd to open CT Netlink sockets into a given
> network namespace. Channel sockets (e.g. UDP) would still be opened into
> the same namespace where conntrackd was started.
> 
> The only binary this patch affects is conntrackd. All other binaries (e.g.
> conntrack, nfct) would still operate in the same namespace where they were
> started.
> 
> To make use of this patch:
> 1. create a network namespace: "ip netns add the_ns"
> 2. add "NetlinkNamespace /var/run/netns/the_ns" line to the conntrackd.conf
> file inside General {...} section.
> 
> Signed-off-by: Ansis Atteka <aatteka@nicira.com>
> ---
>  include/Makefile.am   |    2 +-
>  include/conntrackd.h  |    2 +
>  include/namespace.h   |   12 ++++++
>  src/Makefile.am       |    3 +-
>  src/cthelper.c        |    3 +-
>  src/ctnl.c            |   20 +++++++--
>  src/expect.c          |    4 +-
>  src/external_inject.c |    3 +-
>  src/internal_bypass.c |    5 ++-
>  src/namespace.c       |  112 +++++++++++++++++++++++++++++++++++++++++++++++++
>  src/netlink.c         |    6 ++-
>  src/read_config_lex.l |    1 +
>  src/read_config_yy.y  |    8 +++-
>  src/run.c             |    3 ++
>  src/sync-mode.c       |    4 +-
>  src/sync-notrack.c    |    3 +-
>  16 files changed, 175 insertions(+), 16 deletions(-)
>  create mode 100644 include/namespace.h
>  create mode 100644 src/namespace.c
> 
> diff --git a/include/Makefile.am b/include/Makefile.am
> index 6bd0f7f..e06fd4d 100644
> --- a/include/Makefile.am
> +++ b/include/Makefile.am
> @@ -6,5 +6,5 @@ noinst_HEADERS = alarm.h jhash.h cache.h linux_list.h linux_rbtree.h \
>  		 network.h filter.h queue.h vector.h cidr.h \
>  		 traffic_stats.h netlink.h fds.h event.h bitops.h channel.h \
>  		 process.h origin.h internal.h external.h date.h nfct.h \
> -		 helper.h myct.h stack.h
> +		 helper.h myct.h stack.h namespace.h
>  
> diff --git a/include/conntrackd.h b/include/conntrackd.h
> index 19e613c..c349d72 100644
> --- a/include/conntrackd.h
> +++ b/include/conntrackd.h
> @@ -94,6 +94,7 @@ struct ct_conf {
>  	int channel_type_global;
>  	struct channel_conf channel[MULTICHANNEL_MAX];
>  	struct local_conf local;	/* unix socket facilities */
> +	char netlink_namespace[FILENAME_MAXLEN];
>  	int nice;
>  	int limit;
>  	int refresh;
> @@ -143,6 +144,7 @@ struct ct_conf {
>  #define STATE(x) st.x
>  
>  struct ct_general_state {
> +	int					ns_fd;		/* namespace fd for NL sockets */

We use the same coding style of the Linux kernel. Please, break lines
at 80 chars.

>  	sigset_t 			block;
>  	FILE 				*log;
>  	FILE				*stats_log;
> diff --git a/include/namespace.h b/include/namespace.h
> new file mode 100644
> index 0000000..668a270
> --- /dev/null
> +++ b/include/namespace.h
> @@ -0,0 +1,12 @@
> +#ifndef _NAMESPACE_H_
> +#define _NAMESPACE_H_
> +
> +#include <libmnl/libmnl.h>
> +#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
> +
> +void init_namespaces(void);
> +
> +struct nfct_handle *nfct_open_ns(u_int8_t, unsigned, int);
> +struct mnl_socket *mnl_socket_open_ns(int, int);
> +
> +#endif
> diff --git a/src/Makefile.am b/src/Makefile.am
> index d8074d2..60314ab 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -39,7 +39,8 @@ conntrackd_SOURCES = alarm.c main.c run.c hash.c queue.c rbtree.c \
>  		    external_cache.c external_inject.c \
>  		    internal_cache.c internal_bypass.c \
>  		    read_config_yy.y read_config_lex.l \
> -		    stack.c helpers.c utils.c expect.c
> +		    stack.c helpers.c utils.c expect.c \
> +		    namespace.c
>  
>  # yacc and lex generate dirty code
>  read_config_yy.o read_config_lex.o: AM_CFLAGS += -Wno-missing-prototypes -Wno-missing-declarations -Wno-implicit-function-declaration -Wno-nested-externs -Wno-undef -Wno-redundant-decls
> diff --git a/src/cthelper.c b/src/cthelper.c
> index c119869..b165900 100644
> --- a/src/cthelper.c
> +++ b/src/cthelper.c
> @@ -22,6 +22,7 @@
>  #include "log.h"
>  #include "fds.h"
>  #include "helper.h"
> +#include "namespace.h"
>  
>  #include <unistd.h>
>  #include <fcntl.h>
> @@ -493,7 +494,7 @@ int cthelper_init(void)
>  		return -1;
>  	}
>  
> -	STATE_CTH(nl) = mnl_socket_open(NETLINK_NETFILTER);
> +	STATE_CTH(nl) = mnl_socket_open_ns(NETLINK_NETFILTER, STATE(ns_fd));
>  	if (STATE_CTH(nl) == NULL) {
>  		dlog(LOG_ERR, "cannot open nfq socket");
>  		return -1;
> diff --git a/src/ctnl.c b/src/ctnl.c
> index bb54727..65784c3 100644
> --- a/src/ctnl.c
> +++ b/src/ctnl.c
> @@ -29,6 +29,7 @@
>  #include "origin.h"
>  #include "date.h"
>  #include "internal.h"
> +#include "namespace.h"
>  
>  #include <errno.h>
>  #include <signal.h>
> @@ -399,6 +400,17 @@ static void poll_cb(void *data)
>  
>  int ctnl_init(void)
>  {
> +	if (CONFIG(netlink_namespace)[0]) {
> +		STATE(ns_fd) = open(CONFIG(netlink_namespace), O_RDONLY);
> +		if (STATE(ns_fd) == -1) {
> +			dlog(LOG_ERR, "could not open network namespace %s: %s",
> +				 CONFIG(netlink_namespace), strerror(errno));
> +			return -1;
> +		}
> +	} else {
> +		STATE(ns_fd) = -1;
> +	}
> +
>  	if (CONFIG(flags) & CTD_STATS_MODE)
>  		STATE(mode) = &stats_mode;
>  	else if (CONFIG(flags) & CTD_SYNC_MODE)
> @@ -417,7 +429,7 @@ int ctnl_init(void)
>  	}
>  
>  	/* resynchronize (like 'dump' socket) but it also purges old entries */
> -	STATE(resync) = nfct_open(CONFIG(netlink).subsys_id, 0);
> +	STATE(resync) = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  	if (STATE(resync)== NULL) {
>  		dlog(LOG_ERR, "can't open netlink handler: %s",
>  		     strerror(errno));
> @@ -438,7 +450,7 @@ int ctnl_init(void)
>  	fcntl(nfct_fd(STATE(resync)), F_SETFL, O_NONBLOCK);
>  
>  	if (STATE(mode)->internal->flags & INTERNAL_F_POPULATE) {
> -		STATE(dump) = nfct_open(CONFIG(netlink).subsys_id, 0);
> +		STATE(dump) = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  		if (STATE(dump) == NULL) {
>  			dlog(LOG_ERR, "can't open netlink handler: %s",
>  			     strerror(errno));
> @@ -467,7 +479,7 @@ int ctnl_init(void)
>  		}
>  	}
>  
> -	STATE(get) = nfct_open(CONFIG(netlink).subsys_id, 0);
> +	STATE(get) = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  	if (STATE(get) == NULL) {
>  		dlog(LOG_ERR, "can't open netlink handler: %s",
>  		     strerror(errno));
> @@ -481,7 +493,7 @@ int ctnl_init(void)
>  					exp_get_handler, NULL);
>  	}
>  
> -	STATE(flush) = nfct_open(CONFIG(netlink).subsys_id, 0);
> +	STATE(flush) = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  	if (STATE(flush) == NULL) {
>  		dlog(LOG_ERR, "cannot open flusher handler");
>  		return -1;
> diff --git a/src/expect.c b/src/expect.c
> index 6069770..bedec2c 100644
> --- a/src/expect.c
> +++ b/src/expect.c
> @@ -8,7 +8,9 @@
>   * This code has been sponsored by Vyatta Inc. <http://www.vyatta.com>
>   */
>  
> +#include "conntrackd.h"
>  #include "helper.h"
> +#include "namespace.h"
>  
>  #include <stdio.h>
>  #include <string.h>
> @@ -165,7 +167,7 @@ static int cthelper_expect_cmd(struct nf_expect *exp, int cmd)
>  	int ret;
>  	struct nfct_handle *h;
>  
> -	h = nfct_open(EXPECT, 0);
> +	h = nfct_open_ns(EXPECT, 0, STATE(ns_fd));
>  	if (!h)
>  		return -1;
>  
> diff --git a/src/external_inject.c b/src/external_inject.c
> index 0ad3478..5a6680b 100644
> --- a/src/external_inject.c
> +++ b/src/external_inject.c
> @@ -22,6 +22,7 @@
>  #include "cache.h"
>  #include "origin.h"
>  #include "external.h"
> +#include "namespace.h"
>  #include "netlink.h"
>  
>  #include <libnetfilter_conntrack/libnetfilter_conntrack.h>
> @@ -42,7 +43,7 @@ struct {
>  static int external_inject_init(void)
>  {
>  	/* handler to directly inject conntracks into kernel-space */
> -	inject = nfct_open(CONFIG(netlink).subsys_id, 0);
> +	inject = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  	if (inject == NULL) {
>  		dlog(LOG_ERR, "can't open netlink handler: %s",
>  		     strerror(errno));
> diff --git a/src/internal_bypass.c b/src/internal_bypass.c
> index 1194339..520c55d 100644
> --- a/src/internal_bypass.c
> +++ b/src/internal_bypass.c
> @@ -16,6 +16,7 @@
>  #include "netlink.h"
>  #include "network.h"
>  #include "origin.h"
> +#include "namespace.h"
>  
>  static int internal_bypass_init(void)
>  {
> @@ -52,7 +53,7 @@ static void internal_bypass_ct_dump(int fd, int type)
>  	u_int32_t family = AF_UNSPEC;
>  	int ret;
>  
> -	h = nfct_open(CONFIG(netlink).subsys_id, 0);
> +	h = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  	if (h == NULL) {
>  		dlog(LOG_ERR, "can't allocate memory for the internal cache");
>  		return;
> @@ -183,7 +184,7 @@ static void internal_bypass_exp_dump(int fd, int type)
>  	u_int32_t family = AF_UNSPEC;
>  	int ret;
>  
> -	h = nfct_open(CONFIG(netlink).subsys_id, 0);
> +	h = nfct_open_ns(CONFIG(netlink).subsys_id, 0, STATE(ns_fd));
>  	if (h == NULL) {
>  		dlog(LOG_ERR, "can't allocate memory for the internal cache");
>  		return;
> diff --git a/src/namespace.c b/src/namespace.c
> new file mode 100644
> index 0000000..03db222
> --- /dev/null
> +++ b/src/namespace.c
> @@ -0,0 +1,112 @@
> +/*
> + * Copyright (C) 2012 Nicira, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + *
> + * Authors:
> + *     Ansis Atteka <aatteka@nicira.com>
> + */
> +#define _GNU_SOURCE
> +
> +#include "namespace.h"
> +
> +#include <fcntl.h>
> +#include <sched.h>
> +#include <sys/syscall.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <unistd.h>
> +
> +#include "conntrackd.h"
> +#include "log.h"
> +
> +#ifndef CLONE_NEWNET
> +#define CLONE_NEWNET 0x40000000
> +#endif
> +
> +#ifndef __NR_setns
> +#ifdef __x86_64
> +#define __NR_setns 308
> +#endif
> +#ifdef __i386
> +#define __NR_setns 346
> +#endif
> +#endif

I can see there's some setns wrapper since glibc 2.14 that will make
this portable.

What I would try is to check in configure.ac if setns() exists, if so
use it. Otherwise, check for __NR_setns, if so define setns yourself
in this new namespace.c file. If neither setns() nor __NR_setns
exists, then define setns() to return success and print display error
and exist if NetlinkNamespace is used.

> +
> +#ifdef __NR_setns
> +
> +static int root_fd = -1;

This root_fd should go to STATE(ns).root_fd:

struct ct_state {
...
        struct {
                int cur_fd;     /* current namespace */
                int root_fd;    /* root namespace */
        } ns;

> +
> +void init_namespaces(void) {
> +	root_fd = open("/proc/self/ns/net", O_RDONLY);
> +	if (root_fd == -1) {
> +		dlog(LOG_WARNING, "could not open current namespace");
> +	}
> +}
> +
> +struct nfct_handle *nfct_open_ns(u_int8_t subsys_id, unsigned subscriptions,
> +								 int ns_fd) {
> +	struct nfct_handle *handle = NULL;
> +
> +	if (ns_fd != -1 && syscall(__NR_setns, ns_fd, CLONE_NEWNET)) {
> +		dlog(LOG_ERR, "could not switch between namespaces");
> +	} else {
> +		handle = nfct_open(subsys_id, subscriptions);
> +		if (ns_fd != -1 && syscall(__NR_setns, root_fd, CLONE_NEWNET)) {
> +			dlog(LOG_ERR, "fatal: could not switch back to main namespace");
> +		}
> +	}

Oh, this code above is confusing, please make it more readable, like
this:

	if (ns_fd != -1 && syscall(__NR_setns, ns_fd, CLONE_NEWNET)) {
		dlog(LOG_ERR, "could not switch between namespaces");
                return NULL;
        }

	handle = nfct_open(subsys_id, subscriptions);
	if (ns_fd != -1 && syscall(__NR_setns, root_fd, CLONE_NEWNET)) {
		dlog(LOG_ERR, "could not switch back to main namespace");
	}

And you encapsulate part of that code in some new function like:

int ctd_change_namespace(int fd)
{
	if (fd != -1)
                return 0;

        if (syscall(__NR_setns, fd, CLONE_NEWNET)) {
		dlog(LOG_ERR, "could not switch back to main namespace");
                return -1;
	}

        return 0;
}

That you can reuse over and over again.

> +	return handle;
> +}
> +
> +struct mnl_socket *mnl_socket_open_ns(int bus, int ns_fd) {
> +	struct mnl_socket *handle = NULL;
> +
> +	if (ns_fd != -1 && syscall(__NR_setns, ns_fd, CLONE_NEWNET)) {
> +		dlog(LOG_ERR, "could not switch between namespaces");
> +	} else {
> +		handle = mnl_socket_open(bus);
> +		if (ns_fd != -1 && syscall(__NR_setns, root_fd, CLONE_NEWNET)) {
> +			dlog(LOG_ERR, "fatal: could not switch back to main namespace");
> +		}
> +	}
> +	return handle;

Same thing for this function above.

> +}
> +
> +#else
> +
> +void init_namespaces(void) {
> +}
> +
> +struct nfct_handle *nfct_open_ns(u_int8_t subsys_id, unsigned subscriptions,
> +								 int ns_fd) {
> +	if (ns_fd == -1) {
> +		return nfct_open(subsys_id, subscriptions);
> +	} else {
> +		dlog(LOG_ERR, "network namespaces are not supported on this system");
> +		return NULL;
> +	}
> +}
> +
> +struct mnl_socket *mnl_socket_open_ns(int bus, int ns_fd) {
> +	if (ns_fd == -1) {
> +		return mnl_socket_open(bus);
> +	} else {
> +		dlog(LOG_ERR, "network namespaces are not supported on this system");
> +		return NULL;
> +	}
> +}

You can remove this conditional code above since the #else if you do
something like:

int ctd_change_namespace(int fd)
{
#ifdef SETNS_EXISTS
	if (fd != -1)
                return 0;

        if (syscall(__NR_setns, fd, CLONE_NEWNET)) {
		dlog(LOG_ERR, "could not switch back to main namespace");
                return -1;
	}
#endif
        return 0;
}

That's all by now.