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Date: Wed, 9 Mar 2016 19:47:56 -0800
From: Joe Stringer <joe@....org>
To: Jarno Rajahalme <jarno@....org>, Thomas Graf <tgraf@...g.ch>
Cc: netfilter-devel@...r.kernel.org, netdev <netdev@...r.kernel.org>,
ovs dev <dev@...nvswitch.org>
Subject: Re: [PATCH nf-next v9 8/8] openvswitch: Interface with NAT.
Hi Jarno,
Thanks for working on this. Mostly just a few style things around #ifdefs below.
On 9 March 2016 at 15:10, Jarno Rajahalme <jarno@....org> wrote:
> Extend OVS conntrack interface to cover NAT. New nested
> OVS_CT_ATTR_NAT attribute may be used to include NAT with a CT action.
> A bare OVS_CT_ATTR_NAT only mangles existing and expected connections.
> If OVS_NAT_ATTR_SRC or OVS_NAT_ATTR_DST is included within the nested
> attributes, new (non-committed/non-confirmed) connections are mangled
> according to the rest of the nested attributes.
>
> The corresponding OVS userspace patch series includes test cases (in
> tests/system-traffic.at) that also serve as example uses.
>
> This work extends on a branch by Thomas Graf at
> https://github.com/tgraf/ovs/tree/nat.
Thomas, I guess there was not signoff in these patches so Jarno does
not have your signoff in this patch.
> Signed-off-by: Jarno Rajahalme <jarno@....org>
> ---
> v9: Fixed module dependencies.
>
> include/uapi/linux/openvswitch.h | 49 ++++
> net/openvswitch/Kconfig | 3 +-
> net/openvswitch/conntrack.c | 523 +++++++++++++++++++++++++++++++++++++--
> net/openvswitch/conntrack.h | 3 +-
> 4 files changed, 551 insertions(+), 27 deletions(-)
<snip>
> diff --git a/net/openvswitch/Kconfig b/net/openvswitch/Kconfig
> index cd5fd9d..23471a4 100644
> --- a/net/openvswitch/Kconfig
> +++ b/net/openvswitch/Kconfig
> @@ -6,7 +6,8 @@ config OPENVSWITCH
> tristate "Open vSwitch"
> depends on INET
> depends on !NF_CONNTRACK || \
> - (NF_CONNTRACK && (!NF_DEFRAG_IPV6 || NF_DEFRAG_IPV6))
> + (NF_CONNTRACK && ((!NF_DEFRAG_IPV6 || NF_DEFRAG_IPV6) && \
> + (!NF_NAT || NF_NAT)))
Whitespace.
> select LIBCRC32C
> select MPLS
> select NET_MPLS_GSO
> diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> index 5711f80..6455237 100644
> --- a/net/openvswitch/conntrack.c
> +++ b/net/openvswitch/conntrack.c
<snip>
> struct ovs_ct_len_tbl {
> - size_t maxlen;
> - size_t minlen;
> + int maxlen;
> + int minlen;
> };
Are these changed for a specific reason, or just to use INT_MAX rather
than SIZE_MAX in ovs_ct_len_tbl?
> /* Metadata mark for masked write to conntrack mark */
> @@ -42,15 +52,29 @@ struct md_labels {
> struct ovs_key_ct_labels mask;
> };
>
> +#ifdef CONFIG_NF_NAT_NEEDED
> +enum ovs_ct_nat {
> + OVS_CT_NAT = 1 << 0, /* NAT for committed connections only. */
> + OVS_CT_SRC_NAT = 1 << 1, /* Source NAT for NEW connections. */
> + OVS_CT_DST_NAT = 1 << 2, /* Destination NAT for NEW connections. */
> +};
> +#endif
Here...
> /* Conntrack action context for execution. */
> struct ovs_conntrack_info {
> struct nf_conntrack_helper *helper;
> struct nf_conntrack_zone zone;
> struct nf_conn *ct;
> u8 commit : 1;
> +#ifdef CONFIG_NF_NAT_NEEDED
> + u8 nat : 3; /* enum ovs_ct_nat */
> +#endif
and here.. I wonder if we can trim more of these #ifdefs, for
readability and more compiler coverage if the feature is disabled.
> u16 family;
> struct md_mark mark;
> struct md_labels labels;
> +#ifdef CONFIG_NF_NAT_NEEDED
> + struct nf_nat_range range; /* Only present for SRC NAT and DST NAT. */
> +#endif
> };
(probably not this one, though)
> static void __ovs_ct_free_action(struct ovs_conntrack_info *ct_info);
> @@ -137,12 +161,15 @@ static void __ovs_ct_update_key(struct sw_flow_key *key, u8 state,
> ovs_ct_get_labels(ct, &key->ct.labels);
> }
>
> -/* Update 'key' based on skb->nfct. If 'post_ct' is true, then OVS has
> - * previously sent the packet to conntrack via the ct action.
> +/* Update 'key' based on skb->nfct. If 'post_ct' is true, then OVS has
> + * previously sent the packet to conntrack via the ct action. If
> + * 'keep_nat_flags' is true, the existing NAT flags retained, else they are
> + * initialized from the connection status.
> */
> static void ovs_ct_update_key(const struct sk_buff *skb,
> const struct ovs_conntrack_info *info,
> - struct sw_flow_key *key, bool post_ct)
> + struct sw_flow_key *key, bool post_ct,
> + bool keep_nat_flags)
> {
> const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
> enum ip_conntrack_info ctinfo;
> @@ -160,6 +187,16 @@ static void ovs_ct_update_key(const struct sk_buff *skb,
> */
> if (ct->master)
> state |= OVS_CS_F_RELATED;
> +#ifdef CONFIG_NF_NAT_NEEDED
> + if (keep_nat_flags) {
> + state |= key->ct.state & OVS_CS_F_NAT_MASK;
> + } else {
> + if (ct->status & IPS_SRC_NAT)
> + state |= OVS_CS_F_SRC_NAT;
> + if (ct->status & IPS_DST_NAT)
> + state |= OVS_CS_F_DST_NAT;
> + }
> +#endif
This could be nested within something like if (CONFIG_NF_NAT_NEEDED)
{...} or if (IS_ENABLED(...)) ... to always run the code through the
compiler (which would likely compile out the whole check).
<snip>
> +#ifdef CONFIG_NF_NAT_NEEDED
> + /* Adjust seqs after helper. This is needed due to some helpers (e.g.,
> + * FTP with NAT) adusting the TCP payload size when mangling IP
> + * addresses and/or port numbers in the text-based control connection.
> + */
> + if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
> + !nf_ct_seq_adjust(skb, ct, ctinfo, protoff))
> + return NF_DROP;
> +#endif
> + return NF_ACCEPT;
> }
I suspect this would still compile and work correctly without the ifdef?
<snip>
> +/* Returns NF_DROP if the packet should be dropped, NF_ACCEPT otherwise. */
> +static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
> + const struct ovs_conntrack_info *info,
> + struct sk_buff *skb, struct nf_conn *ct,
> + enum ip_conntrack_info ctinfo)
> +{
> + enum nf_nat_manip_type maniptype;
> + int err;
> +
> + if (nf_ct_is_untracked(ct)) {
> + /* A NAT action may only be performed on tracked packets. */
> + return NF_ACCEPT;
> + }
> +
> + /* Add NAT extension if not confirmed yet. */
> + if (!nf_ct_is_confirmed(ct) && !nf_ct_nat_ext_add(ct))
> + return NF_ACCEPT; /* Can't NAT. */
> +
> + /* Determine NAT type.
> + * Check if the NAT type can be deduced from the tracked connection.
> + * Make sure expected traffic is NATted only when committing.
> + */
> + if (info->nat & OVS_CT_NAT && ctinfo != IP_CT_NEW &&
> + ct->status & IPS_NAT_MASK &&
> + (!(ct->status & IPS_EXPECTED_BIT) || info->commit)) {
> + /* NAT an established or related connection like before. */
> + if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY)
> + /* This is the REPLY direction for a connection
> + * for which NAT was applied in the forward
> + * direction. Do the reverse NAT.
> + */
> + maniptype = ct->status & IPS_SRC_NAT
> + ? NF_NAT_MANIP_DST : NF_NAT_MANIP_SRC;
> + else
> + maniptype = ct->status & IPS_SRC_NAT
> + ? NF_NAT_MANIP_SRC : NF_NAT_MANIP_DST;
> + } else if (info->nat & OVS_CT_SRC_NAT) {
> + maniptype = NF_NAT_MANIP_SRC;
> + } else if (info->nat & OVS_CT_DST_NAT) {
> + maniptype = NF_NAT_MANIP_DST;
> + } else {
> + return NF_ACCEPT; /* Connection is not NATed. */
> + }
> + err = ovs_ct_nat_execute(skb, ct, ctinfo, &info->range, maniptype);
> +
> + /* Mark NAT done if successful and update the flow key. */
> + if (err == NF_ACCEPT)
> + ovs_nat_update_key(key, skb, maniptype);
> +
> + return err;
> +}
> +#endif
<snip>
> - /* Call the helper only if we did nf_conntrack_in() above ('!cached')
> - * for confirmed connections, but only when committing for unconfirmed
> - * connections.
> - */
> ct = nf_ct_get(skb, &ctinfo);
> - if (ct && (nf_ct_is_confirmed(ct) ? !cached : info->commit) &&
> - ovs_ct_helper(skb, info->family) != NF_ACCEPT) {
> - WARN_ONCE(1, "helper rejected packet");
> - return -EINVAL;
> + if (ct) {
> +#ifdef CONFIG_NF_NAT_NEEDED
> + /* Packets starting a new connection must be NATted before the
> + * helper, so that the helper knows about the NAT. We enforce
> + * this by delaying both NAT and helper calls for unconfirmed
> + * connections until the committing CT action. For later
> + * packets NAT and Helper may be called in either order.
> + *
> + * NAT will be done only if the CT action has NAT, and only
> + * once per packet (per zone), as guarded by the NAT bits in
> + * the key->ct.state.
> + */
> + if (info->nat && !(key->ct.state & OVS_CS_F_NAT_MASK) &&
> + (nf_ct_is_confirmed(ct) || info->commit) &&
> + ovs_ct_nat(net, key, info, skb, ct, ctinfo) != NF_ACCEPT) {
> + return -EINVAL;
> + }
> +#endif
Again, I think the #ifdefs are probably unnecessary. Currently
ovs_ct_nat() is conditionally compiled out, but we could provide a
stub version for the !CONFIG_NF_NAT_NEEDED case instead, placed
immediately below the actual implementation further up:
...
#else /* !CONFIG_NF_NAT_NEEDED */
static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
const struct ovs_conntrack_info *info,
struct sk_buff *skb, struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
return NF_ACCEPT;
}
#endif
Thanks,
Joe
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