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Commit cae3a262 authored by Joe Stringer's avatar Joe Stringer Committed by David S. Miller
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openvswitch: Allow attaching helpers to ct action 



Add support for using conntrack helpers to assist protocol detection.
The new OVS_CT_ATTR_HELPER attribute of the CT action specifies a helper
to be used for this connection. If no helper is specified, then helpers
will be automatically applied as per the sysctl configuration of
net.netfilter.nf_conntrack_helper.

The helper may be specified as part of the conntrack action, eg:
ct(helper=ftp). Initial packets for related connections should be
committed to allow later packets for the flow to be considered
established.

Example ovs-ofctl flows allowing FTP connections from ports 1->2:
in_port=1,tcp,action=ct(helper=ftp,commit),2
in_port=2,tcp,ct_state=-trk,action=ct(recirc)
in_port=2,tcp,ct_state=+trk-new+est,action=1
in_port=2,tcp,ct_state=+trk+rel,action=1

Signed-off-by: default avatarJoe Stringer <joestringer@nicira.com>
Acked-by: default avatarThomas Graf <tgraf@suug.ch>
Acked-by: default avatarPravin B Shelar <pshelar@nicira.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c2ac6673

include/uapi/linux/openvswitch.h

+3 −0
Original line number Diff line number Diff line
@@ -626,6 +626,7 @@ struct ovs_action_hash { 
 * @OVS_CT_ATTR_LABEL: %OVS_CT_LABEL_LEN value followed by %OVS_CT_LABEL_LEN

 * mask. For each bit set in the mask, the corresponding bit in the value is

 * copied to the connection tracking label field in the connection.

 * @OVS_CT_ATTR_HELPER: variable length string defining conntrack ALG.

 */

enum ovs_ct_attr {

	OVS_CT_ATTR_UNSPEC,
@@ -633,6 +634,8 @@ enum ovs_ct_attr { 
	OVS_CT_ATTR_ZONE,       /* u16 zone id. */

	OVS_CT_ATTR_MARK,       /* mark to associate with this connection. */

	OVS_CT_ATTR_LABEL,      /* label to associate with this connection. */

	OVS_CT_ATTR_HELPER,     /* netlink helper to assist detection of

				   related connections. */

	__OVS_CT_ATTR_MAX

};

net/openvswitch/conntrack.c

+107 −2
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/openvswitch.h>

#include <net/ip.h>

#include <net/netfilter/nf_conntrack_core.h>

#include <net/netfilter/nf_conntrack_helper.h>

#include <net/netfilter/nf_conntrack_labels.h>

#include <net/netfilter/nf_conntrack_zones.h>

#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
@@ -43,6 +44,7 @@ struct md_label { 


/* Conntrack action context for execution. */

struct ovs_conntrack_info {

	struct nf_conntrack_helper *helper;

	struct nf_conntrack_zone zone;

	struct nf_conn *ct;

	u32 flags;
@@ -234,6 +236,51 @@ static int ovs_ct_set_label(struct sk_buff *skb, struct sw_flow_key *key, 
	return 0;

}



/* 'skb' should already be pulled to nh_ofs. */

static int ovs_ct_helper(struct sk_buff *skb, u16 proto)

{

	const struct nf_conntrack_helper *helper;

	const struct nf_conn_help *help;

	enum ip_conntrack_info ctinfo;

	unsigned int protoff;

	struct nf_conn *ct;



	ct = nf_ct_get(skb, &ctinfo);

	if (!ct || ctinfo == IP_CT_RELATED_REPLY)

		return NF_ACCEPT;



	help = nfct_help(ct);

	if (!help)

		return NF_ACCEPT;



	helper = rcu_dereference(help->helper);

	if (!helper)

		return NF_ACCEPT;



	switch (proto) {

	case NFPROTO_IPV4:

		protoff = ip_hdrlen(skb);

		break;

	case NFPROTO_IPV6: {

		u8 nexthdr = ipv6_hdr(skb)->nexthdr;

		__be16 frag_off;



		protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),

					   &nexthdr, &frag_off);

		if (protoff < 0 || (frag_off & htons(~0x7)) != 0) {

			pr_debug("proto header not found\n");

			return NF_ACCEPT;

		}

		break;

	}

	default:

		WARN_ONCE(1, "helper invoked on non-IP family!");

		return NF_DROP;

	}



	return helper->help(skb, protoff, ct, ctinfo);

}



static int handle_fragments(struct net *net, struct sw_flow_key *key,

			    u16 zone, struct sk_buff *skb)

{
@@ -306,6 +353,13 @@ static bool skb_nfct_cached(const struct net *net, const struct sk_buff *skb, 
		return false;

	if (!nf_ct_zone_equal_any(info->ct, nf_ct_zone(ct)))

		return false;

	if (info->helper) {

		struct nf_conn_help *help;



		help = nf_ct_ext_find(ct, NF_CT_EXT_HELPER);

		if (help && rcu_access_pointer(help->helper) != info->helper)

			return false;

	}



	return true;

}
@@ -334,6 +388,11 @@ static int __ovs_ct_lookup(struct net *net, const struct sw_flow_key *key, 
		if (nf_conntrack_in(net, info->family, NF_INET_PRE_ROUTING,

				    skb) != NF_ACCEPT)

			return -ENOENT;



		if (ovs_ct_helper(skb, info->family) != NF_ACCEPT) {

			WARN_ONCE(1, "helper rejected packet");

			return -EINVAL;

		}

	}



	return 0;
@@ -442,6 +501,30 @@ int ovs_ct_execute(struct net *net, struct sk_buff *skb, 
	return err;

}



static int ovs_ct_add_helper(struct ovs_conntrack_info *info, const char *name,

			     const struct sw_flow_key *key, bool log)

{

	struct nf_conntrack_helper *helper;

	struct nf_conn_help *help;



	helper = nf_conntrack_helper_try_module_get(name, info->family,

						    key->ip.proto);

	if (!helper) {

		OVS_NLERR(log, "Unknown helper \"%s\"", name);

		return -EINVAL;

	}



	help = nf_ct_helper_ext_add(info->ct, helper, GFP_KERNEL);

	if (!help) {

		module_put(helper->me);

		return -ENOMEM;

	}



	rcu_assign_pointer(help->helper, helper);

	info->helper = helper;

	return 0;

}



static const struct ovs_ct_len_tbl ovs_ct_attr_lens[OVS_CT_ATTR_MAX + 1] = {

	[OVS_CT_ATTR_FLAGS]	= { .minlen = sizeof(u32),

				    .maxlen = sizeof(u32) },
@@ -451,10 +534,12 @@ static const struct ovs_ct_len_tbl ovs_ct_attr_lens[OVS_CT_ATTR_MAX + 1] = { 
				    .maxlen = sizeof(struct md_mark) },

	[OVS_CT_ATTR_LABEL]	= { .minlen = sizeof(struct md_label),

				    .maxlen = sizeof(struct md_label) },

	[OVS_CT_ATTR_HELPER]	= { .minlen = 1,

				    .maxlen = NF_CT_HELPER_NAME_LEN }

};



static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info,

		    bool log)

		    const char **helper, bool log)

{

	struct nlattr *a;

	int rem;
@@ -502,6 +587,13 @@ static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info, 
			break;

		}

#endif

		case OVS_CT_ATTR_HELPER:

			*helper = nla_data(a);

			if (!memchr(*helper, '\0', nla_len(a))) {

				OVS_NLERR(log, "Invalid conntrack helper");

				return -EINVAL;

			}

			break;

		default:

			OVS_NLERR(log, "Unknown conntrack attr (%d)",

				  type);
@@ -542,6 +634,7 @@ int ovs_ct_copy_action(struct net *net, const struct nlattr *attr, 
		       struct sw_flow_actions **sfa,  bool log)

{

	struct ovs_conntrack_info ct_info;

	const char *helper = NULL;

	u16 family;

	int err;
@@ -557,7 +650,7 @@ int ovs_ct_copy_action(struct net *net, const struct nlattr *attr, 
	nf_ct_zone_init(&ct_info.zone, NF_CT_DEFAULT_ZONE_ID,

			NF_CT_DEFAULT_ZONE_DIR, 0);



	err = parse_ct(attr, &ct_info, log);

	err = parse_ct(attr, &ct_info, &helper, log);

	if (err)

		return err;
@@ -567,6 +660,11 @@ int ovs_ct_copy_action(struct net *net, const struct nlattr *attr, 
		OVS_NLERR(log, "Failed to allocate conntrack template");

		return -ENOMEM;

	}

	if (helper) {

		err = ovs_ct_add_helper(&ct_info, helper, key, log);

		if (err)

			goto err_free_ct;

	}



	err = ovs_nla_add_action(sfa, OVS_ACTION_ATTR_CT, &ct_info,

				 sizeof(ct_info), log);
@@ -603,6 +701,11 @@ int ovs_ct_action_to_attr(const struct ovs_conntrack_info *ct_info, 
	    nla_put(skb, OVS_CT_ATTR_LABEL, sizeof(ct_info->label),

		    &ct_info->label))

		return -EMSGSIZE;

	if (ct_info->helper) {

		if (nla_put_string(skb, OVS_CT_ATTR_HELPER,

				   ct_info->helper->name))

			return -EMSGSIZE;

	}



	nla_nest_end(skb, start);
@@ -613,6 +716,8 @@ void ovs_ct_free_action(const struct nlattr *a) 
{

	struct ovs_conntrack_info *ct_info = nla_data(a);



	if (ct_info->helper)

		module_put(ct_info->helper->me);

	if (ct_info->ct)

		nf_ct_put(ct_info->ct);

}