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: Joe Stringer <joestringer@xxxxxxxxxx>
---
v2-v3: No change.
v4: Change error code for unknown helper ENOENT->EINVAL.
v5: Fix rcu access of helpers.
Rebase.
---
include/uapi/linux/openvswitch.h | 3 ++
net/openvswitch/conntrack.c | 109 ++++++++++++++++++++++++++++++++++++++-
2 files changed, 110 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index 9d52058..32e07d8 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -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
};
diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 8cb0987..ac6d1d2 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>
@@ -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;
@@ -213,6 +215,51 @@ 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)
{
@@ -285,6 +332,13 @@ 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;
}
@@ -313,6 +367,11 @@ 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;
@@ -421,6 +480,30 @@ err:
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) },
@@ -430,10 +513,12 @@ 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;
@@ -481,6 +566,13 @@ 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);
@@ -521,6 +613,7 @@ 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;
@@ -536,7 +629,7 @@ 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;
@@ -546,6 +639,11 @@ 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);
@@ -582,6 +680,11 @@ 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);
@@ -592,6 +695,8 @@ 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
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