From cae3a2627520c3795b54533c5328b77af3405dbe Mon Sep 17 00:00:00 2001 From: Joe Stringer Date: Wed, 26 Aug 2015 11:31:53 -0700 Subject: 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: Joe Stringer Acked-by: Thomas Graf Acked-by: Pravin B Shelar Signed-off-by: David S. Miller --- 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 9d52058a9330..32e07d8cbaf4 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 a0417fb33d1d..890d3eedb447 100644 --- a/net/openvswitch/conntrack.c +++ b/net/openvswitch/conntrack.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -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 @@ 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) }, @@ -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); } -- cgit v1.2.3-59-g8ed1b