netdev - [RFC v2 10/19] batman-adv: Add fragmentation mesh genl configuration

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Message-Id: <20181123161359.13342-11-sven@narfation.org>
Date:   Fri, 23 Nov 2018 17:13:50 +0100
From:   Sven Eckelmann <sven@...fation.org>
To:     b.a.t.m.a.n@...ts.open-mesh.org
Cc:     Jiri Pirko <jiri@...lanox.com>, netdev@...r.kernel.org,
        Sven Eckelmann <sven@...fation.org>
Subject: [RFC v2 10/19] batman-adv: Add fragmentation mesh genl configuration

The mesh interface can fragment unicast packets when the packet size
exceeds the outgoing slave/hard-interface MTU.

The BATADV_CMD_SET_MESH/BATADV_CMD_GET_MESH commands allow to set/get the
configuration of this feature using the BATADV_ATTR_FRAGMENTATION
attribute. Setting the u8 to zero will disable this feature and setting it
to something else is enabling this feature.

Cc: Jiri Pirko <jiri@...lanox.com>
Signed-off-by: Sven Eckelmann <sven@...fation.org>
---
 include/uapi/linux/batman_adv.h |  7 +++++++
 net/batman-adv/netlink.c        | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/uapi/linux/batman_adv.h b/include/uapi/linux/batman_adv.h
index 618c727c..5c58d3b6 100644
--- a/include/uapi/linux/batman_adv.h
+++ b/include/uapi/linux/batman_adv.h
@@ -395,6 +395,13 @@ enum batadv_nl_attrs {
 	 */
 	BATADV_ATTR_DISTRIBUTED_ARP_TABLE,
 
+	/**
+	 * @BATADV_ATTR_FRAGMENTATION: whether the data traffic going through
+	 *  the mesh will be fragmented or silently discarded if the packet size
+	 *  exceeds the outgoing interface MTU.
+	 */
+	BATADV_ATTR_FRAGMENTATION,
+
 	/* add attributes above here, update the policy in netlink.c */
 
 	/**
diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
index d93039b2..d7d5f196 100644
--- a/net/batman-adv/netlink.c
+++ b/net/batman-adv/netlink.c
@@ -146,6 +146,7 @@ static const struct nla_policy batadv_netlink_policy[NUM_BATADV_ATTR] = {
 	[BATADV_ATTR_BONDING]			= { .type = NLA_U8 },
 	[BATADV_ATTR_BRIDGE_LOOP_AVOIDANCE]	= { .type = NLA_U8 },
 	[BATADV_ATTR_DISTRIBUTED_ARP_TABLE]	= { .type = NLA_U8 },
+	[BATADV_ATTR_FRAGMENTATION]		= { .type = NLA_U8 },
 };
 
 /**
@@ -297,6 +298,10 @@ static int batadv_netlink_mesh_put(struct sk_buff *msg,
 		goto nla_put_failure;
 #endif /* CONFIG_BATMAN_ADV_DAT */
 
+	if (nla_put_u8(msg, BATADV_ATTR_FRAGMENTATION,
+		       !!atomic_read(&bat_priv->fragmentation)))
+		goto nla_put_failure;
+
 	batadv_hardif_put(primary_if);
 
 	genlmsg_end(msg, hdr);
@@ -430,6 +435,13 @@ static int batadv_netlink_set_mesh(struct sk_buff *skb, struct genl_info *info)
 	}
 #endif /* CONFIG_BATMAN_ADV_DAT */
 
+	if (info->attrs[BATADV_ATTR_FRAGMENTATION]) {
+		attr = info->attrs[BATADV_ATTR_FRAGMENTATION];
+
+		atomic_set(&bat_priv->fragmentation, !!nla_get_u8(attr));
+		batadv_update_min_mtu(bat_priv->soft_iface);
+	}
+
 	batadv_netlink_notify_mesh(bat_priv);
 
 	return 0;
-- 
2.19.1