[PATCH net-next 9/9] openvswitch: Allow attaching helpers to ct action

Joe Stringer
2015-07-30T18:12:43Z

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.

Example ODP 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(1)
recirc_id=1,in_port=2,tcp,ct_state=+trk-new+est,action=1
recirc_id=1,in_port=2,tcp,ct_state=+trk+rel,action=1

Signed-off-by: Joe Stringer <joestringer@nicira.com>
---
include/uapi/linux/openvswitch.h | 1 +
net/openvswitch/Kconfig | 1 +
net/openvswitch/conntrack.c | 109 ++++++++++++++++++++++++++++++++++++++-
3 files changed, 109 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index f360dc9..e816170 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -626,6 +626,7 @@ enum ovs_ct_attr {
OVS_CT_ATTR_UNSPEC,
OVS_CT_ATTR_FLAGS, /* u8 bitmask of OVS_CT_F_*. */
OVS_CT_ATTR_ZONE, /* u16 zone id. */
+ OVS_CT_ATTR_HELPER,
__OVS_CT_ATTR_MAX
};

diff --git a/net/openvswitch/Kconfig b/net/openvswitch/Kconfig
index 92bb3d3..c25b221 100644
--- a/net/openvswitch/Kconfig
+++ b/net/openvswitch/Kconfig
@@ -36,6 +36,7 @@ config OPENVSWITCH_CONNTRACK
bool "Open vSwitch conntrack action support"
depends on OPENVSWITCH
depends on NF_CONNTRACK
+ depends on NETFILTER_XTABLES
default OPENVSWITCH
---help---
If you say Y here, then Open vSwitch module will be able to pass
diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 5acc59a..e7a5ca7 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -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>
@@ -30,6 +31,7 @@ struct ovs_ct_len_tbl {
};

struct ovs_conntrack_info {
+ struct nf_conntrack_helper *helper;
struct nf_conn *ct;
u32 flags;
u16 zone;
@@ -158,6 +160,51 @@ bool ovs_ct_state_valid(const struct sw_flow_key *key)
return __ovs_ct_state_valid(key->ct.state);
}

+/* '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)
{
@@ -232,6 +279,13 @@ static bool skb_nfct_cached(const struct net *net, const struct sk_buff *skb,
}
if (info->zone != 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 && help->helper != info->helper)
+ return false;
+ }

return true;
}
@@ -288,6 +342,11 @@ 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;
@@ -437,15 +496,41 @@ int ovs_ct_set_label(struct sk_buff *skb, struct sw_flow_key *key,
#endif
}

+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 -ENOENT;
+ }
+
+ help = nf_ct_helper_ext_add(info->ct, helper, GFP_KERNEL);
+ if (!help) {
+ module_put(helper->me);
+ return -ENOMEM;
+ }
+
+ 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) },
[OVS_CT_ATTR_ZONE] = { .minlen = sizeof(u16),
.maxlen = sizeof(u16) },
+ [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;
@@ -477,6 +562,13 @@ static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info,
case OVS_CT_ATTR_FLAGS:
info->flags = nla_get_u32(a);
break;
+ 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);
@@ -518,6 +610,7 @@ int ovs_ct_copy_action(struct net *net, const struct nlattr *attr,
{
struct ovs_conntrack_info ct_info;
struct nf_conntrack_tuple t;
+ const char *helper = NULL;
u16 family;
int err;

@@ -530,7 +623,7 @@ int ovs_ct_copy_action(struct net *net, const struct nlattr *attr,
memset(&ct_info, 0, sizeof(ct_info));
ct_info.family = family;

- err = parse_ct(attr, &ct_info, log);
+ err = parse_ct(attr, &ct_info, &helper, log);
if (err)
return err;

@@ -542,6 +635,11 @@ int ovs_ct_copy_action(struct net *net, const struct nlattr *attr,
OVS_NLERR(log, "Failed to allocate conntrack template");
return PTR_ERR(ct_info.ct);
}
+ 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);
@@ -570,6 +668,11 @@ int ovs_ct_action_to_attr(const struct ovs_conntrack_info *ct_info,
if (nla_put_u16(skb, OVS_CT_ATTR_ZONE, ct_info->zone))
return -EMSGSIZE;
#endif
+ if (ct_info->helper) {
+ if (nla_put_string(skb, OVS_CT_ATTR_HELPER,
+ ct_info->helper->name))
+ return -EMSGSIZE;
+ }

nla_nest_end(skb, start);

@@ -580,6 +683,8 @@ 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);
}
--
2.1.4