[PATCH net-next] openvswitch: report features supported by the kernel datapath

* [PATCH net-next] openvswitch: report features supported by the kernel datapath
@ 2015-10-08 13:53 Jiri Benc
  2015-10-08 22:40 ` Jesse Gross
  0 siblings, 1 reply; 5+ messages in thread
From: Jiri Benc @ 2015-10-08 13:53 UTC (permalink / raw)
  To: netdev; +Cc: dev, Pravin Shelar, Jesse Gross, Thomas Graf

Allow the user space to query what features are supported by the openvswitch
module. This will be used to allow or disallow certain configurations and/or
switch between newer and older APIs depending on what the kernel supports.

Two features are reported as supported by this patch: lwtunnel and IPv6
tunneling support. Theoretically, we could merge these two, as any of them
implies the other with this patch applied, but it's better to keep them
separate: kernel 4.3 supports lwtunnels but not IPv6 for ovs, and the
separation of the two flags allows us to backport a version of this patch
to 4.3 should the need arise.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
---
This is intentionally submitted to net-next. Kernel 4.3 will be fine without
this feature (but despite that, I'd like to keep the two flags separate).
---
 include/uapi/linux/openvswitch.h | 12 ++++++++++++
 net/openvswitch/datapath.c       | 21 ++++++++++++++++++---
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index 32e07d8cbaf4..3d8d00b6e55d 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -73,6 +73,10 @@ enum ovs_datapath_cmd {
  * datapath.  Always present in notifications.
  * @OVS_DP_ATTR_MEGAFLOW_STATS: Statistics about mega flow masks usage for the
  * datapath. Always present in notifications.
+ * @OVS_DP_ATTR_KERNEL_FEATURES: Bitmask of features that the datapath
+ * supports.  When creating a datapath, this is a minimal feature set
+ * requested, the request will fail if it cannot be honored.  On get
+ * operations, this contains all features supported by the datapath.
  *
  * These attributes follow the &struct ovs_header within the Generic Netlink
  * payload for %OVS_DP_* commands.
@@ -84,6 +88,7 @@ enum ovs_datapath_attr {
 	OVS_DP_ATTR_STATS,		/* struct ovs_dp_stats */
 	OVS_DP_ATTR_MEGAFLOW_STATS,	/* struct ovs_dp_megaflow_stats */
 	OVS_DP_ATTR_USER_FEATURES,	/* OVS_DP_F_*  */
+	OVS_DP_ATTR_KERNEL_FEATURES,	/* OVS_DP_KF_* */
 	__OVS_DP_ATTR_MAX
 };
 
@@ -121,6 +126,13 @@ struct ovs_vport_stats {
 /* Allow datapath to associate multiple Netlink PIDs to each vport */
 #define OVS_DP_F_VPORT_PIDS	(1 << 1)
 
+/* Datapath features */
+#define OVS_DP_KF_LWTUNNEL	(1ULL << 0)  /* lwtunnel interface supported */
+#define OVS_DP_KF_IPV6_TUNNEL	(1ULL << 1)  /* IPv6 tunneling supported */
+
+#define OVS_DP_KF_ALL		(OVS_DP_KF_LWTUNNEL | \
+				 OVS_DP_KF_IPV6_TUNNEL)
+
 /* Fixed logical ports. */
 #define OVSP_LOCAL      ((__u32)0)
 
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index a75828091e21..896435779fc8 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1439,6 +1439,7 @@ static size_t ovs_dp_cmd_msg_size(void)
 	msgsize += nla_total_size(sizeof(struct ovs_dp_stats));
 	msgsize += nla_total_size(sizeof(struct ovs_dp_megaflow_stats));
 	msgsize += nla_total_size(sizeof(u32)); /* OVS_DP_ATTR_USER_FEATURES */
+	msgsize += nla_total_size(sizeof(u64)); /* OVS_DP_ATTR_KERNEL_FEATURES */
 
 	return msgsize;
 }
@@ -1476,6 +1477,9 @@ static int ovs_dp_cmd_fill_info(struct datapath *dp, struct sk_buff *skb,
 	if (nla_put_u32(skb, OVS_DP_ATTR_USER_FEATURES, dp->user_features))
 		goto nla_put_failure;
 
+	if (nla_put_u64(skb, OVS_DP_ATTR_KERNEL_FEATURES, OVS_DP_KF_ALL))
+		goto nla_put_failure;
+
 	genlmsg_end(skb, ovs_header);
 	return 0;
 
@@ -1526,6 +1530,13 @@ static void ovs_dp_change(struct datapath *dp, struct nlattr *a[])
 		dp->user_features = nla_get_u32(a[OVS_DP_ATTR_USER_FEATURES]);
 }
 
+static bool ovs_dp_kernel_features_ok(struct nlattr *a[])
+{
+	if (!a[OVS_DP_ATTR_KERNEL_FEATURES])
+		return true;
+	return !(nla_get_u64(a[OVS_DP_ATTR_KERNEL_FEATURES]) & ~OVS_DP_KF_ALL);
+}
+
 static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
@@ -1536,9 +1547,10 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 	struct ovs_net *ovs_net;
 	int err, i;
 
-	err = -EINVAL;
 	if (!a[OVS_DP_ATTR_NAME] || !a[OVS_DP_ATTR_UPCALL_PID])
-		goto err;
+		return -EINVAL;
+	if (!ovs_dp_kernel_features_ok(a))
+		return -EOPNOTSUPP;
 
 	reply = ovs_dp_cmd_alloc_info(info);
 	if (!reply)
@@ -1626,7 +1638,6 @@ err_free_dp:
 	kfree(dp);
 err_free_reply:
 	kfree_skb(reply);
-err:
 	return err;
 }
 
@@ -1694,6 +1705,9 @@ static int ovs_dp_cmd_set(struct sk_buff *skb, struct genl_info *info)
 	struct datapath *dp;
 	int err;
 
+	if (!ovs_dp_kernel_features_ok(info->attrs))
+		return -EOPNOTSUPP;
+
 	reply = ovs_dp_cmd_alloc_info(info);
 	if (!reply)
 		return -ENOMEM;
@@ -1777,6 +1791,7 @@ static const struct nla_policy datapath_policy[OVS_DP_ATTR_MAX + 1] = {
 	[OVS_DP_ATTR_NAME] = { .type = NLA_NUL_STRING, .len = IFNAMSIZ - 1 },
 	[OVS_DP_ATTR_UPCALL_PID] = { .type = NLA_U32 },
 	[OVS_DP_ATTR_USER_FEATURES] = { .type = NLA_U32 },
+	[OVS_DP_ATTR_KERNEL_FEATURES] = { .type = NLA_U64 },
 };
 
 static const struct genl_ops dp_datapath_genl_ops[] = {
-- 
1.8.3.1

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