openvswitch: Add conntrack action

Expose the kernel connection tracker via OVS. Userspace components can
make use of the CT action to populate the connection state (ct_state)
field for a flow. This state can be subsequently matched.

Exposed connection states are OVS_CS_F_*:
- NEW (0x01) - Beginning of a new connection.
- ESTABLISHED (0x02) - Part of an existing connection.
- RELATED (0x04) - Related to an established connection.
- INVALID (0x20) - Could not track the connection for this packet.
- REPLY_DIR (0x40) - This packet is in the reply direction for the flow.
- TRACKED (0x80) - This packet has been sent through conntrack.

When the CT action is executed by itself, it will send the packet
through the connection tracker and populate the ct_state field with one
or more of the connection state flags above. The CT action will always
set the TRACKED bit.

When the COMMIT flag is passed to the conntrack action, this specifies
that information about the connection should be stored. This allows
subsequent packets for the same (or related) connections to be
correlated with this connection. Sending subsequent packets for the
connection through conntrack allows the connection tracker to consider
the packets as ESTABLISHED, RELATED, and/or REPLY_DIR.

The CT action may optionally take a zone to track the flow within. This
allows connections with the same 5-tuple to be kept logically separate
from connections in other zones. If the zone is specified, then the
"ct_zone" match field will be subsequently populated with the zone id.

IP fragments are handled by transparently assembling them as part of the
CT action. The maximum received unit (MRU) size is tracked so that
refragmentation can occur during output.

IP frag handling contributed by Andy Zhou.

Based on original design by Justin Pettit.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Signed-off-by: Justin Pettit <jpettit@nicira.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 454 insertions, 0 deletions

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
new file mode 100644
index 000000000000..1189fd50f1cf
--- /dev/null
+++ b/net/openvswitch/conntrack.c
@@ -0,0 +1,454 @@
+/*
+ * Copyright (c) 2015 Nicira, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/openvswitch.h>
+#include <net/ip.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_zones.h>
+#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
+
+#include "datapath.h"
+#include "conntrack.h"
+#include "flow.h"
+#include "flow_netlink.h"
+
+struct ovs_ct_len_tbl {
+        size_t maxlen;
+        size_t minlen;
+};
+
+/* Conntrack action context for execution. */
+struct ovs_conntrack_info {
+        struct nf_conntrack_zone zone;
+        struct nf_conn *ct;
+        u32 flags;
+        u16 family;
+};
+
+static u16 key_to_nfproto(const struct sw_flow_key *key)
+{
+        switch (ntohs(key->eth.type)) {
+        case ETH_P_IP:
+                return NFPROTO_IPV4;
+        case ETH_P_IPV6:
+                return NFPROTO_IPV6;
+        default:
+                return NFPROTO_UNSPEC;
+        }
+}
+
+/* Map SKB connection state into the values used by flow definition. */
+static u8 ovs_ct_get_state(enum ip_conntrack_info ctinfo)
+{
+        u8 ct_state = OVS_CS_F_TRACKED;
+
+        switch (ctinfo) {
+        case IP_CT_ESTABLISHED_REPLY:
+        case IP_CT_RELATED_REPLY:
+        case IP_CT_NEW_REPLY:
+                ct_state |= OVS_CS_F_REPLY_DIR;
+                break;
+        default:
+                break;
+        }
+
+        switch (ctinfo) {
+        case IP_CT_ESTABLISHED:
+        case IP_CT_ESTABLISHED_REPLY:
+                ct_state |= OVS_CS_F_ESTABLISHED;
+                break;
+        case IP_CT_RELATED:
+        case IP_CT_RELATED_REPLY:
+                ct_state |= OVS_CS_F_RELATED;
+                break;
+        case IP_CT_NEW:
+        case IP_CT_NEW_REPLY:
+                ct_state |= OVS_CS_F_NEW;
+                break;
+        default:
+                break;
+        }
+
+        return ct_state;
+}
+
+static void __ovs_ct_update_key(struct sw_flow_key *key, u8 state,
+                                const struct nf_conntrack_zone *zone)
+{
+        key->ct.state = state;
+        key->ct.zone = zone->id;
+}
+
+/* Update 'key' based on skb->nfct. If 'post_ct' is true, then OVS has
+ * previously sent the packet to conntrack via the ct action.
+ */
+static void ovs_ct_update_key(const struct sk_buff *skb,
+                              struct sw_flow_key *key, bool post_ct)
+{
+        const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
+        enum ip_conntrack_info ctinfo;
+        struct nf_conn *ct;
+        u8 state = 0;
+
+        ct = nf_ct_get(skb, &ctinfo);
+        if (ct) {
+                state = ovs_ct_get_state(ctinfo);
+                if (ct->master)
+                        state |= OVS_CS_F_RELATED;
+                zone = nf_ct_zone(ct);
+        } else if (post_ct) {
+                state = OVS_CS_F_TRACKED | OVS_CS_F_INVALID;
+        }
+        __ovs_ct_update_key(key, state, zone);
+}
+
+void ovs_ct_fill_key(const struct sk_buff *skb, struct sw_flow_key *key)
+{
+        ovs_ct_update_key(skb, key, false);
+}
+
+int ovs_ct_put_key(const struct sw_flow_key *key, struct sk_buff *skb)
+{
+        if (nla_put_u8(skb, OVS_KEY_ATTR_CT_STATE, key->ct.state))
+                return -EMSGSIZE;
+
+        if (IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES) &&
+            nla_put_u16(skb, OVS_KEY_ATTR_CT_ZONE, key->ct.zone))
+                return -EMSGSIZE;
+
+        return 0;
+}
+
+static int handle_fragments(struct net *net, struct sw_flow_key *key,
+                            u16 zone, struct sk_buff *skb)
+{
+        struct ovs_skb_cb ovs_cb = *OVS_CB(skb);
+
+        if (key->eth.type == htons(ETH_P_IP)) {
+                enum ip_defrag_users user = IP_DEFRAG_CONNTRACK_IN + zone;
+                int err;
+
+                memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
+                err = ip_defrag(skb, user);
+                if (err)
+                        return err;
+
+                ovs_cb.mru = IPCB(skb)->frag_max_size;
+        } else if (key->eth.type == htons(ETH_P_IPV6)) {
+#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
+                enum ip6_defrag_users user = IP6_DEFRAG_CONNTRACK_IN + zone;
+                struct sk_buff *reasm;
+
+                memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
+                reasm = nf_ct_frag6_gather(skb, user);
+                if (!reasm)
+                        return -EINPROGRESS;
+
+                if (skb == reasm)
+                        return -EINVAL;
+
+                key->ip.proto = ipv6_hdr(reasm)->nexthdr;
+                skb_morph(skb, reasm);
+                consume_skb(reasm);
+                ovs_cb.mru = IP6CB(skb)->frag_max_size;
+#else
+                return -EPFNOSUPPORT;
+#endif
+        } else {
+                return -EPFNOSUPPORT;
+        }
+
+        key->ip.frag = OVS_FRAG_TYPE_NONE;
+        skb_clear_hash(skb);
+        skb->ignore_df = 1;
+        *OVS_CB(skb) = ovs_cb;
+
+        return 0;
+}
+
+static struct nf_conntrack_expect *
+ovs_ct_expect_find(struct net *net, const struct nf_conntrack_zone *zone,
+                   u16 proto, const struct sk_buff *skb)
+{
+        struct nf_conntrack_tuple tuple;
+
+        if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), proto, &tuple))
+                return NULL;
+        return __nf_ct_expect_find(net, zone, &tuple);
+}
+
+/* Determine whether skb->nfct is equal to the result of conntrack lookup. */
+static bool skb_nfct_cached(const struct net *net, const struct sk_buff *skb,
+                            const struct ovs_conntrack_info *info)
+{
+        enum ip_conntrack_info ctinfo;
+        struct nf_conn *ct;
+
+        ct = nf_ct_get(skb, &ctinfo);
+        if (!ct)
+                return false;
+        if (!net_eq(net, read_pnet(&ct->ct_net)))
+                return false;
+        if (!nf_ct_zone_equal_any(info->ct, nf_ct_zone(ct)))
+                return false;
+
+        return true;
+}
+
+static int __ovs_ct_lookup(struct net *net, const struct sw_flow_key *key,
+                           const struct ovs_conntrack_info *info,
+                           struct sk_buff *skb)
+{
+        /* If we are recirculating packets to match on conntrack fields and
+         * committing with a separate conntrack action,  then we don't need to
+         * actually run the packet through conntrack twice unless it's for a
+         * different zone.
+         */
+        if (!skb_nfct_cached(net, skb, info)) {
+                struct nf_conn *tmpl = info->ct;
+
+                /* Associate skb with specified zone. */
+                if (tmpl) {
+                        if (skb->nfct)
+                                nf_conntrack_put(skb->nfct);
+                        nf_conntrack_get(&tmpl->ct_general);
+                        skb->nfct = &tmpl->ct_general;
+                        skb->nfctinfo = IP_CT_NEW;
+                }
+
+                if (nf_conntrack_in(net, info->family, NF_INET_PRE_ROUTING,
+                                    skb) != NF_ACCEPT)
+                        return -ENOENT;
+        }
+
+        return 0;
+}
+
+/* Lookup connection and read fields into key. */
+static int ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
+                         const struct ovs_conntrack_info *info,
+                         struct sk_buff *skb)
+{
+        struct nf_conntrack_expect *exp;
+
+        exp = ovs_ct_expect_find(net, &info->zone, info->family, skb);
+        if (exp) {
+                u8 state;
+
+                state = OVS_CS_F_TRACKED | OVS_CS_F_NEW | OVS_CS_F_RELATED;
+                __ovs_ct_update_key(key, state, &info->zone);
+        } else {
+                int err;
+
+                err = __ovs_ct_lookup(net, key, info, skb);
+                if (err)
+                        return err;
+
+                ovs_ct_update_key(skb, key, true);
+        }
+
+        return 0;
+}
+
+/* Lookup connection and confirm if unconfirmed. */
+static int ovs_ct_commit(struct net *net, struct sw_flow_key *key,
+                         const struct ovs_conntrack_info *info,
+                         struct sk_buff *skb)
+{
+        u8 state;
+        int err;
+
+        state = key->ct.state;
+        if (key->ct.zone == info->zone.id &&
+            ((state & OVS_CS_F_TRACKED) && !(state & OVS_CS_F_NEW))) {
+                /* Previous lookup has shown that this connection is already
+                 * tracked and committed. Skip committing.
+                 */
+                return 0;
+        }
+
+        err = __ovs_ct_lookup(net, key, info, skb);
+        if (err)
+                return err;
+        if (nf_conntrack_confirm(skb) != NF_ACCEPT)
+                return -EINVAL;
+
+        ovs_ct_update_key(skb, key, true);
+
+        return 0;
+}
+
+int ovs_ct_execute(struct net *net, struct sk_buff *skb,
+                   struct sw_flow_key *key,
+                   const struct ovs_conntrack_info *info)
+{
+        int nh_ofs;
+        int err;
+
+        /* The conntrack module expects to be working at L3. */
+        nh_ofs = skb_network_offset(skb);
+        skb_pull(skb, nh_ofs);
+
+        if (key->ip.frag != OVS_FRAG_TYPE_NONE) {
+                err = handle_fragments(net, key, info->zone.id, skb);
+                if (err)
+                        return err;
+        }
+
+        if (info->flags & OVS_CT_F_COMMIT)
+                err = ovs_ct_commit(net, key, info, skb);
+        else
+                err = ovs_ct_lookup(net, key, info, skb);
+
+        skb_push(skb, nh_ofs);
+        return err;
+}
+
+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) },
+};
+
+static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info,
+                    bool log)
+{
+        struct nlattr *a;
+        int rem;
+
+        nla_for_each_nested(a, attr, rem) {
+                int type = nla_type(a);
+                int maxlen = ovs_ct_attr_lens[type].maxlen;
+                int minlen = ovs_ct_attr_lens[type].minlen;
+
+                if (type > OVS_CT_ATTR_MAX) {
+                        OVS_NLERR(log,
+                                  "Unknown conntrack attr (type=%d, max=%d)",
+                                  type, OVS_CT_ATTR_MAX);
+                        return -EINVAL;
+                }
+                if (nla_len(a) < minlen || nla_len(a) > maxlen) {
+                        OVS_NLERR(log,
+                                  "Conntrack attr type has unexpected length (type=%d, length=%d, expected=%d)",
+                                  type, nla_len(a), maxlen);
+                        return -EINVAL;
+                }
+
+                switch (type) {
+                case OVS_CT_ATTR_FLAGS:
+                        info->flags = nla_get_u32(a);
+                        break;
+#ifdef CONFIG_NF_CONNTRACK_ZONES
+                case OVS_CT_ATTR_ZONE:
+                        info->zone.id = nla_get_u16(a);
+                        break;
+#endif
+                default:
+                        OVS_NLERR(log, "Unknown conntrack attr (%d)",
+                                  type);
+                        return -EINVAL;
+                }
+        }
+
+        if (rem > 0) {
+                OVS_NLERR(log, "Conntrack attr has %d unknown bytes", rem);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+bool ovs_ct_verify(enum ovs_key_attr attr)
+{
+        if (attr == OVS_KEY_ATTR_CT_STATE)
+                return true;
+        if (IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES) &&
+            attr == OVS_KEY_ATTR_CT_ZONE)
+                return true;
+
+        return false;
+}
+
+int ovs_ct_copy_action(struct net *net, const struct nlattr *attr,
+                       const struct sw_flow_key *key,
+                       struct sw_flow_actions **sfa,  bool log)
+{
+        struct ovs_conntrack_info ct_info;
+        u16 family;
+        int err;
+
+        family = key_to_nfproto(key);
+        if (family == NFPROTO_UNSPEC) {
+                OVS_NLERR(log, "ct family unspecified");
+                return -EINVAL;
+        }
+
+        memset(&ct_info, 0, sizeof(ct_info));
+        ct_info.family = family;
+
+        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);
+        if (err)
+                return err;
+
+        /* Set up template for tracking connections in specific zones. */
+        ct_info.ct = nf_ct_tmpl_alloc(net, &ct_info.zone, GFP_KERNEL);
+        if (!ct_info.ct) {
+                OVS_NLERR(log, "Failed to allocate conntrack template");
+                return -ENOMEM;
+        }
+
+        err = ovs_nla_add_action(sfa, OVS_ACTION_ATTR_CT, &ct_info,
+                                 sizeof(ct_info), log);
+        if (err)
+                goto err_free_ct;
+
+        __set_bit(IPS_CONFIRMED_BIT, &ct_info.ct->status);
+        nf_conntrack_get(&ct_info.ct->ct_general);
+        return 0;
+err_free_ct:
+        nf_conntrack_free(ct_info.ct);
+        return err;
+}
+
+int ovs_ct_action_to_attr(const struct ovs_conntrack_info *ct_info,
+                          struct sk_buff *skb)
+{
+        struct nlattr *start;
+
+        start = nla_nest_start(skb, OVS_ACTION_ATTR_CT);
+        if (!start)
+                return -EMSGSIZE;
+
+        if (nla_put_u32(skb, OVS_CT_ATTR_FLAGS, ct_info->flags))
+                return -EMSGSIZE;
+        if (IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES) &&
+            nla_put_u16(skb, OVS_CT_ATTR_ZONE, ct_info->zone.id))
+                return -EMSGSIZE;
+
+        nla_nest_end(skb, start);
+
+        return 0;
+}
+
+void ovs_ct_free_action(const struct nlattr *a)
+{
+        struct ovs_conntrack_info *ct_info = nla_data(a);
+
+        if (ct_info->ct)
+                nf_ct_put(ct_info->ct);
+}