[PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[Fredrik Markstrom]

Currently veth drops all packets larger then the mtu set on the receiving
end of the pair. This is inconsistent with most hardware ethernet drivers.

This patch set adds a new driver attribute to set the maximum size of
received packet to make it possible to create configurations similar to
those possible with (most) hardware ethernet interfaces.

The set consists of two patches. The first one adding a parameter do the
dev_forward_skb functions to specify the maximum packet size, the
second one implents a new attribute (VETH_MRU) in the veth driver.

Fredrik Markstrom (1):
  veth: Added attribute to set maximum receive size on veth interfaces

Fredrik Markström (1):
  net: Added mtu parameter to dev_forward_skb calls

 drivers/net/ipvlan/ipvlan_core.c |  7 ++++---
 drivers/net/macvlan.c            |  4 ++--
 drivers/net/veth.c               | 45 +++++++++++++++++++++++++++++++++++++++-
 include/linux/netdevice.h        | 10 ++++-----
 include/uapi/linux/veth.h        |  1 +
 net/bridge/br_forward.c          |  4 ++--
 net/core/dev.c                   | 17 +++++++++------
 net/core/filter.c                |  4 ++--
 net/l2tp/l2tp_eth.c              |  2 +-
 9 files changed, 72 insertions(+), 22 deletions(-)

-- 
2.11.0

[PATCH 1/2] net: Added mtu parameter to dev_forward_skb calls

[Fredrik Markstrom]

From: Fredrik Markström <fredrik.markstrom@gmail.com>

is_skb_forwardable() currently checks if the packet size is <= mtu of
the receiving interface. This is not consistent with most of the hardware
ethernet drivers that happily receives packets larger then MTU.

This patch adds a parameter to dev_forward_skb and is_skb_forwardable so
that the caller can override this packet size limit.

Signed-off-by: Fredrik Markstrom <fredrik.markstrom@gmail.com>
---
 drivers/net/ipvlan/ipvlan_core.c |  7 ++++---
 drivers/net/macvlan.c            |  4 ++--
 drivers/net/veth.c               |  2 +-
 include/linux/netdevice.h        | 10 +++++-----
 net/bridge/br_forward.c          |  4 ++--
 net/core/dev.c                   | 17 +++++++++++------
 net/core/filter.c                |  4 ++--
 net/l2tp/l2tp_eth.c              |  2 +-
 8 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ipvlan/ipvlan_core.c b/drivers/net/ipvlan/ipvlan_core.c
index 1f3295e274d0..dbbe48ade204 100644
--- a/drivers/net/ipvlan/ipvlan_core.c
+++ b/drivers/net/ipvlan/ipvlan_core.c
@@ -234,7 +234,8 @@ void ipvlan_process_multicast(struct work_struct *work)
 				nskb->pkt_type = pkt_type;
 				nskb->dev = ipvlan->dev;
 				if (tx_pkt)
-					ret = dev_forward_skb(ipvlan->dev, nskb);
+					ret = dev_forward_skb(ipvlan->dev,
+							      nskb, 0);
 				else
 					ret = netif_rx(nskb);
 			}
@@ -301,7 +302,7 @@ static int ipvlan_rcv_frame(struct ipvl_addr *addr, struct sk_buff **pskb,
 
 	if (local) {
 		skb->pkt_type = PACKET_HOST;
-		if (dev_forward_skb(ipvlan->dev, skb) == NET_RX_SUCCESS)
+		if (dev_forward_skb(ipvlan->dev, skb, 0) == NET_RX_SUCCESS)
 			success = true;
 	} else {
 		ret = RX_HANDLER_ANOTHER;
@@ -547,7 +548,7 @@ static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 		 * the skb for the main-dev. At the RX side we just return
 		 * RX_PASS for it to be processed further on the stack.
 		 */
-		return dev_forward_skb(ipvlan->phy_dev, skb);
+		return dev_forward_skb(ipvlan->phy_dev, skb, 0);
 
 	} else if (is_multicast_ether_addr(eth->h_dest)) {
 		ipvlan_skb_crossing_ns(skb, NULL);
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 9261722960a7..4db2876c1e44 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -202,7 +202,7 @@ static int macvlan_broadcast_one(struct sk_buff *skb,
 	struct net_device *dev = vlan->dev;
 
 	if (local)
-		return __dev_forward_skb(dev, skb);
+		return __dev_forward_skb(dev, skb, 0);
 
 	skb->dev = dev;
 	if (ether_addr_equal_64bits(eth->h_dest, dev->broadcast))
@@ -495,7 +495,7 @@ static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)
 		dest = macvlan_hash_lookup(port, eth->h_dest);
 		if (dest && dest->mode == MACVLAN_MODE_BRIDGE) {
 			/* send to lowerdev first for its network taps */
-			dev_forward_skb(vlan->lowerdev, skb);
+			dev_forward_skb(vlan->lowerdev, skb, 0);
 
 			return NET_XMIT_SUCCESS;
 		}
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 8c39d6d690e5..561da3a63b8a 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -116,7 +116,7 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto drop;
 	}
 
-	if (likely(dev_forward_skb(rcv, skb) == NET_RX_SUCCESS)) {
+	if (likely(dev_forward_skb(rcv, skb, 0) == NET_RX_SUCCESS)) {
 		struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);
 
 		u64_stats_update_begin(&stats->syncp);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 97456b2539e4..f207b083ffec 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3282,16 +3282,16 @@ int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags);
 struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev);
 struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 				    struct netdev_queue *txq, int *ret);
-int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
-int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
+int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb, int mtu);
+int dev_forward_skb(struct net_device *dev, struct sk_buff *skb, int mtu);
 bool is_skb_forwardable(const struct net_device *dev,
-			const struct sk_buff *skb);
+			const struct sk_buff *skb, int mtu);
 
 static __always_inline int ____dev_forward_skb(struct net_device *dev,
-					       struct sk_buff *skb)
+					       struct sk_buff *skb, int mtu)
 {
 	if (skb_orphan_frags(skb, GFP_ATOMIC) ||
-	    unlikely(!is_skb_forwardable(dev, skb))) {
+	    unlikely(!is_skb_forwardable(dev, skb, mtu))) {
 		atomic_long_inc(&dev->rx_dropped);
 		kfree_skb(skb);
 		return NET_RX_DROP;
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 902af6ba481c..a1a38bb0d890 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -35,7 +35,7 @@ static inline int should_deliver(const struct net_bridge_port *p,
 
 int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
-	if (!is_skb_forwardable(skb->dev, skb))
+	if (!is_skb_forwardable(skb->dev, skb, 0))
 		goto drop;
 
 	skb_push(skb, ETH_HLEN);
@@ -96,7 +96,7 @@ static void __br_forward(const struct net_bridge_port *to,
 		net = dev_net(indev);
 	} else {
 		if (unlikely(netpoll_tx_running(to->br->dev))) {
-			if (!is_skb_forwardable(skb->dev, skb)) {
+			if (!is_skb_forwardable(skb->dev, skb, skb->dev_mtu)) {
 				kfree_skb(skb);
 			} else {
 				skb_push(skb, ETH_HLEN);
diff --git a/net/core/dev.c b/net/core/dev.c
index 533a6d6f6092..f7c53d7c8e26 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1767,14 +1767,18 @@ static inline void net_timestamp_set(struct sk_buff *skb)
 			__net_timestamp(SKB);		\
 	}						\
 
-bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb)
+bool is_skb_forwardable(const struct net_device *dev,
+			const struct sk_buff *skb, int mtu)
 {
 	unsigned int len;
 
 	if (!(dev->flags & IFF_UP))
 		return false;
 
-	len = dev->mtu + dev->hard_header_len + VLAN_HLEN;
+	if (mtu == 0)
+		mtu = dev->mtu;
+
+	len = mtu + dev->hard_header_len + VLAN_HLEN;
 	if (skb->len <= len)
 		return true;
 
@@ -1788,9 +1792,9 @@ bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(is_skb_forwardable);
 
-int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
+int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb, int mtu)
 {
-	int ret = ____dev_forward_skb(dev, skb);
+	int ret = ____dev_forward_skb(dev, skb, mtu);
 
 	if (likely(!ret)) {
 		skb->protocol = eth_type_trans(skb, dev);
@@ -1806,6 +1810,7 @@ EXPORT_SYMBOL_GPL(__dev_forward_skb);
  *
  * @dev: destination network device
  * @skb: buffer to forward
+ * @mtu: Maximum size to forward. If 0 dev->mtu is used.
  *
  * return values:
  *	NET_RX_SUCCESS	(no congestion)
@@ -1819,9 +1824,9 @@ EXPORT_SYMBOL_GPL(__dev_forward_skb);
  * we have to clear all information in the skb that could
  * impact namespace isolation.
  */
-int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
+int dev_forward_skb(struct net_device *dev, struct sk_buff *skb, int mtu)
 {
-	return __dev_forward_skb(dev, skb) ?: netif_rx_internal(skb);
+	return __dev_forward_skb(dev, skb, mtu) ?: netif_rx_internal(skb);
 }
 EXPORT_SYMBOL_GPL(dev_forward_skb);
 
diff --git a/net/core/filter.c b/net/core/filter.c
index ebaeaf2e46e8..3f3eb26e7ea1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1632,13 +1632,13 @@ static const struct bpf_func_proto bpf_csum_update_proto = {
 
 static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb)
 {
-	return dev_forward_skb(dev, skb);
+	return dev_forward_skb(dev, skb, 0);
 }
 
 static inline int __bpf_rx_skb_no_mac(struct net_device *dev,
 				      struct sk_buff *skb)
 {
-	int ret = ____dev_forward_skb(dev, skb);
+	int ret = ____dev_forward_skb(dev, skb, 0);
 
 	if (likely(!ret)) {
 		skb->dev = dev;
diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
index 6fd41d7afe1e..1258555b6578 100644
--- a/net/l2tp/l2tp_eth.c
+++ b/net/l2tp/l2tp_eth.c
@@ -164,7 +164,7 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb,
 	skb_dst_drop(skb);
 	nf_reset(skb);
 
-	if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
+	if (dev_forward_skb(dev, skb, 0) == NET_RX_SUCCESS) {
 		atomic_long_inc(&priv->rx_packets);
 		atomic_long_add(data_len, &priv->rx_bytes);
 	} else {
-- 
2.11.0

Re: [PATCH 1/2] net: Added mtu parameter to dev_forward_skb calls

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1341 bytes --]

Hi Fredrik,

[auto build test ERROR on net/master]
[also build test ERROR on v4.11 next-20170510]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Fredrik-Markstrom/net-Added-mtu-parameter-to-dev_forward_skb-calls/20170509-231142
config: x86_64-rhel (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   net//bridge/br_forward.c: In function '__br_forward':
>> net//bridge/br_forward.c:99:46: error: 'struct sk_buff' has no member named 'dev_mtu'
       if (!is_skb_forwardable(skb->dev, skb, skb->dev_mtu)) {
                                                 ^~

vim +99 net//bridge/br_forward.c

    93			}
    94			br_hook = NF_BR_FORWARD;
    95			skb_forward_csum(skb);
    96			net = dev_net(indev);
    97		} else {
    98			if (unlikely(netpoll_tx_running(to->br->dev))) {
  > 99				if (!is_skb_forwardable(skb->dev, skb, skb->dev_mtu)) {
   100					kfree_skb(skb);
   101				} else {
   102					skb_push(skb, ETH_HLEN);

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 39200 bytes --]

[PATCH 2/2] veth: Added attribute to set maximum receive size on veth interfaces

[Fredrik Markstrom]

Currently veth drops all packet larger then the mtu set on the receiving
end of the pair. This is inconsistent with most hardware ethernet drivers.
This patch adds a new driver attribute to set the maximum size of received
packet to make it possible to create configurations similar to those
possible with (most) hardware ethernet interfaces.

Signed-off-by: Fredrik Markstrom <fredrik.markstrom@gmail.com>
---
 drivers/net/veth.c        | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 include/uapi/linux/veth.h |  1 +
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 561da3a63b8a..5669286dd531 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -33,6 +33,7 @@ struct veth_priv {
 	struct net_device __rcu	*peer;
 	atomic64_t		dropped;
 	unsigned		requested_headroom;
+	int			mru;
 };
 
 /*
@@ -106,6 +107,7 @@ static const struct ethtool_ops veth_ethtool_ops = {
 static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
+	struct veth_priv *rcv_priv;
 	struct net_device *rcv;
 	int length = skb->len;
 
@@ -115,8 +117,10 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 		kfree_skb(skb);
 		goto drop;
 	}
+	rcv_priv = netdev_priv(rcv);
 
-	if (likely(dev_forward_skb(rcv, skb, 0) == NET_RX_SUCCESS)) {
+	if (likely(dev_forward_skb(rcv, skb, rcv_priv->mru) ==
+		   NET_RX_SUCCESS)) {
 		struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);
 
 		u64_stats_update_begin(&stats->syncp);
@@ -346,6 +350,11 @@ static int veth_validate(struct nlattr *tb[], struct nlattr *data[])
 		if (!is_valid_veth_mtu(nla_get_u32(tb[IFLA_MTU])))
 			return -EINVAL;
 	}
+
+	if (tb[VETH_MRU])
+		if (!is_valid_veth_mtu(nla_get_u32(tb[VETH_MRU])))
+			return -EINVAL;
+
 	return 0;
 }
 
@@ -450,10 +459,15 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 	 */
 
 	priv = netdev_priv(dev);
+	if (tb[VETH_MRU])
+		priv->mru = nla_get_u32(tb[VETH_MRU]);
 	rcu_assign_pointer(priv->peer, peer);
 
 	priv = netdev_priv(peer);
+	if (tbp[VETH_MRU])
+		priv->mru = nla_get_u32(tbp[VETH_MRU]);
 	rcu_assign_pointer(priv->peer, dev);
+
 	return 0;
 
 err_register_dev:
@@ -489,8 +503,34 @@ static void veth_dellink(struct net_device *dev, struct list_head *head)
 	}
 }
 
+static int veth_changelink(struct net_device *dev,
+			   struct nlattr *tb[], struct nlattr *data[])
+{
+	struct veth_priv *priv = netdev_priv(dev);
+
+	if (data && data[VETH_MRU])
+		priv->mru = nla_get_u32(data[VETH_MRU]);
+	return 0;
+}
+
+static size_t veth_get_size(const struct net_device *dev)
+{
+	return nla_total_size(4);/* VETH_MRU */
+}
+
+static int veth_fill_info(struct sk_buff *skb,
+			  const struct net_device *dev)
+{
+	struct veth_priv *priv = netdev_priv(dev);
+
+	if (nla_put_u32(skb, VETH_MRU, priv->mru))
+		return -EMSGSIZE;
+	return 0;
+}
+
 static const struct nla_policy veth_policy[VETH_INFO_MAX + 1] = {
 	[VETH_INFO_PEER]	= { .len = sizeof(struct ifinfomsg) },
+	[VETH_MRU]		= { .type = NLA_U32 },
 };
 
 static struct net *veth_get_link_net(const struct net_device *dev)
@@ -508,9 +548,12 @@ static struct rtnl_link_ops veth_link_ops = {
 	.validate	= veth_validate,
 	.newlink	= veth_newlink,
 	.dellink	= veth_dellink,
+	.changelink	= veth_changelink,
 	.policy		= veth_policy,
 	.maxtype	= VETH_INFO_MAX,
 	.get_link_net	= veth_get_link_net,
+	.get_size	= veth_get_size,
+	.fill_info	= veth_fill_info,
 };
 
 /*
diff --git a/include/uapi/linux/veth.h b/include/uapi/linux/veth.h
index 3354c1eb424e..8665b260f156 100644
--- a/include/uapi/linux/veth.h
+++ b/include/uapi/linux/veth.h
@@ -4,6 +4,7 @@
 enum {
 	VETH_INFO_UNSPEC,
 	VETH_INFO_PEER,
+	VETH_MRU,
 
 	__VETH_INFO_MAX
 #define VETH_INFO_MAX	(__VETH_INFO_MAX - 1)
-- 
2.11.0

Support for VETH_MRU in libnl

[Fredrik Markstrom]

---
 include/linux/if_link.h           |   1 +
 include/netlink-private/types.h   |   1 +
 include/netlink/route/link/veth.h |   4 ++
 lib/route/link.c                  |   4 ++
 lib/route/link/veth.c             | 141 +++++++++++++++++++++++++++++---------
 5 files changed, 118 insertions(+), 33 deletions(-)

diff --git a/include/linux/if_link.h b/include/linux/if_link.h
index 8b84939..b9859bd 100644
--- a/include/linux/if_link.h
+++ b/include/linux/if_link.h
@@ -316,6 +316,7 @@ struct ifla_vxlan_port_range {
 enum {
 	VETH_INFO_UNSPEC,
 	VETH_INFO_PEER,
+	VETH_MRU,
 
 	__VETH_INFO_MAX
 #define VETH_INFO_MAX   (__VETH_INFO_MAX - 1)
diff --git a/include/netlink-private/types.h b/include/netlink-private/types.h
index 3ff4fe1..c97090b 100644
--- a/include/netlink-private/types.h
+++ b/include/netlink-private/types.h
@@ -165,6 +165,7 @@ struct rtnl_link
 	uint32_t			l_flags;
 	uint32_t			l_change;
 	uint32_t 			l_mtu;
+	uint32_t 			l_mru;
 	uint32_t			l_link;
 	uint32_t			l_txqlen;
 	uint32_t			l_weight;
diff --git a/include/netlink/route/link/veth.h b/include/netlink/route/link/veth.h
index 35c2345..58eeb98 100644
--- a/include/netlink/route/link/veth.h
+++ b/include/netlink/route/link/veth.h
@@ -29,6 +29,10 @@ extern struct rtnl_link *rtnl_link_veth_get_peer(struct rtnl_link *);
 extern int rtnl_link_veth_add(struct nl_sock *sock, const char *name,
 			      const char *peer, pid_t pid);
 
+extern int rtnl_link_veth_set_mru(struct rtnl_link *, uint32_t);
+
+extern uint32_t rtnl_link_veth_get_mru(struct rtnl_link *);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/route/link.c b/lib/route/link.c
index 3d31ffc..3cdacbb 100644
--- a/lib/route/link.c
+++ b/lib/route/link.c
@@ -61,6 +61,7 @@
 #define LINK_ATTR_PHYS_PORT_ID	(1 << 28)
 #define LINK_ATTR_NS_FD		(1 << 29)
 #define LINK_ATTR_NS_PID	(1 << 30)
+#define LINK_ATTR_MRU		(1 << 31)
 
 static struct nl_cache_ops rtnl_link_ops;
 static struct nl_object_ops link_obj_ops;
@@ -1255,6 +1256,9 @@ int rtnl_link_fill_info(struct nl_msg *msg, struct rtnl_link *link)
 	if (link->ce_mask & LINK_ATTR_MTU)
 		NLA_PUT_U32(msg, IFLA_MTU, link->l_mtu);
 
+	if (link->ce_mask & LINK_ATTR_MRU)
+		NLA_PUT_U32(msg, IFLA_MTU, link->l_mru);
+
 	if (link->ce_mask & LINK_ATTR_TXQLEN)
 		NLA_PUT_U32(msg, IFLA_TXQLEN, link->l_txqlen);
 
diff --git a/lib/route/link/veth.c b/lib/route/link/veth.c
index e7e4a26..5dc15af 100644
--- a/lib/route/link/veth.c
+++ b/lib/route/link/veth.c
@@ -33,16 +33,62 @@
 
 #include <linux/if_link.h>
 
+#define VETH_HAS_MRU		(1<<0)
+
+struct veth_info
+{
+	struct rtnl_link *peer;
+	uint32_t		vei_mru;
+	uint32_t		vei_mask;
+};
+
 static struct nla_policy veth_policy[VETH_INFO_MAX+1] = {
 	[VETH_INFO_PEER]	= { .minlen = sizeof(struct ifinfomsg) },
+	[VETH_MRU]		= { .type = NLA_U32 },
 };
 
+static int veth_alloc(struct rtnl_link *link)
+{
+	struct rtnl_link *peer;
+	struct veth_info *vei = link->l_info;
+	int err;
+
+	/* return early if we are in recursion */
+	if (vei && vei->peer)
+		return 0;
+
+	if (!(peer = rtnl_link_alloc()))
+		return -NLE_NOMEM;
+
+	if ((vei = calloc(1, sizeof(*vei))) == NULL)
+	  return -NLE_NOMEM;
+
+	/* We don't need to hold a reference here, as link and
+	 * its peer should always be freed together.
+	 */
+	vei->peer = link;
+
+	peer->l_info = vei;
+	if ((err = rtnl_link_set_type(peer, "veth")) < 0) {
+		rtnl_link_put(peer);
+		return err;
+	}
+
+	if ((vei = calloc(1, sizeof(*vei))) == NULL)
+	  return -NLE_NOMEM;
+
+	vei->peer = peer;
+	link->l_info = vei;
+	return 0;
+}
+
 static int veth_parse(struct rtnl_link *link, struct nlattr *data,
 		      struct nlattr *xstats)
 {
 	struct nlattr *tb[VETH_INFO_MAX+1];
 	struct nlattr *peer_tb[IFLA_MAX + 1];
-	struct rtnl_link *peer = link->l_info;
+	struct veth_info *vei = link->l_info;
+	struct rtnl_link *peer = vei->peer;
 	int err;
 
 	NL_DBG(3, "Parsing veth link info");
@@ -50,6 +96,14 @@ static int veth_parse(struct rtnl_link *link, struct nlattr *data,
 	if ((err = nla_parse_nested(tb, VETH_INFO_MAX, data, veth_policy)) < 0)
 		goto errout;
 
+	if ((err = veth_alloc(link)) < 0)
+		goto errout;
+
+	if (tb[VETH_MRU]) {
+		vei->vei_mru = nla_get_u32(tb[VETH_MRU]);
+		vei->vei_mask |= VETH_HAS_MRU;
+	}
+
 	if (tb[VETH_INFO_PEER]) {
 		struct nlattr *nla_peer;
 		struct ifinfomsg *ifi;
@@ -86,7 +140,8 @@ static void veth_dump_line(struct rtnl_link *link, struct nl_dump_params *p)
 
 static void veth_dump_details(struct rtnl_link *link, struct nl_dump_params *p)
 {
-	struct rtnl_link *peer = link->l_info;
+	struct veth_info *vei = link->l_info;
+	struct rtnl_link *peer = vei->peer;
 	char *name;
 	name = rtnl_link_get_name(peer);
 	nl_dump(p, "      peer ");
@@ -98,7 +153,14 @@ static void veth_dump_details(struct rtnl_link *link, struct nl_dump_params *p)
 
 static int veth_clone(struct rtnl_link *dst, struct rtnl_link *src)
 {
-	struct rtnl_link *dst_peer = NULL, *src_peer = src->l_info;
+	struct veth_info *src_vei = src->l_info;
+	struct veth_info *dst_vei = dst->l_info;
+	struct rtnl_link *dst_peer = NULL, *src_peer = src_vei->peer;
+
+
+	printf("veth_clone not implemented\n");
+
+	// FIXME:
 
 	/* we are calling nl_object_clone() recursively, this should
 	 * happen only once */
@@ -116,7 +178,8 @@ static int veth_clone(struct rtnl_link *dst, struct rtnl_link *src)
 
 static int veth_put_attrs(struct nl_msg *msg, struct rtnl_link *link)
 {
-	struct rtnl_link *peer = link->l_info;
+	struct veth_info *vei = link->l_info;
+	struct rtnl_link *peer = vei->peer;
 	struct ifinfomsg ifi;
 	struct nlattr *data, *info_peer;
 
@@ -135,44 +198,31 @@ static int veth_put_attrs(struct nl_msg *msg, struct rtnl_link *link)
 		return -NLE_MSGSIZE;
 	rtnl_link_fill_info(msg, peer);
 	nla_nest_end(msg, info_peer);
-	nla_nest_end(msg, data);
 
-	return 0;
-}
-
-static int veth_alloc(struct rtnl_link *link)
-{
-	struct rtnl_link *peer;
-	int err;
-
-	/* return early if we are in recursion */
-	if (link->l_info)
-		return 0;
+	if (vei->vei_mask & VETH_HAS_MRU)
+		NLA_PUT_U32(msg, VETH_MRU, vei->vei_mru);
 
-	if (!(peer = rtnl_link_alloc()))
-		return -NLE_NOMEM;
+	nla_nest_end(msg, data);
 
-	/* We don't need to hold a reference here, as link and
-	 * its peer should always be freed together.
-	 */
-	peer->l_info = link;
-	if ((err = rtnl_link_set_type(peer, "veth")) < 0) {
-		rtnl_link_put(peer);
-		return err;
-	}
+nla_put_failure:
 
-	link->l_info = peer;
 	return 0;
 }
 
 static void veth_free(struct rtnl_link *link)
 {
-	struct rtnl_link *peer = link->l_info;
-	if (peer) {
+	struct veth_info *vei = link->l_info;
+	if (vei) {
+		struct rtnl_link *peer = vei->peer;
+		if (peer) {
+			vei->peer = NULL;
+			rtnl_link_put(peer);
+			/* avoid calling this recursively */
+			free(peer->l_info);
+			peer->l_info = NULL;
+		}
+		free(vei);
 		link->l_info = NULL;
-		/* avoid calling this recursively */
-		peer->l_info = NULL;
-		rtnl_link_put(peer);
 	}
 	/* the caller should finally free link */
 }
@@ -195,7 +245,7 @@ static struct rtnl_link_info_ops veth_info_ops = {
 #define IS_VETH_LINK_ASSERT(link) \
 	if ((link)->l_info_ops != &veth_info_ops) { \
 		APPBUG("Link is not a veth link. set type \"veth\" first."); \
-		return NULL; \
+		return -NLE_OPNOTSUPP; \
 	}
 /** @endcond */
 
@@ -293,6 +343,31 @@ int rtnl_link_veth_add(struct nl_sock *sock, const char *name,
 	return err;
 }
 
+int rtnl_link_veth_set_mru(struct rtnl_link *link, uint32_t mru)
+{
+	struct veth_info *vei = link->l_info;
+
+	IS_VETH_LINK_ASSERT(link);
+
+	vei->vei_mru = mru;
+	vei->vei_mask |= VETH_HAS_MRU;
+
+	return 0;
+}
+
+uint32_t rtnl_link_veth_get_mru(struct rtnl_link *link)
+{
+	struct veth_info *vei = link->l_info;
+
+	IS_VETH_LINK_ASSERT(link);
+
+	if (vei->vei_mask & VETH_HAS_MRU)
+		return vei->vei_mru;
+	else
+		return 0;
+}
+
+
 /** @} */
 
 static void __init veth_init(void)
-- 
2.10.1

Re: [PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[Stephen Hemminger]

On Tue,  9 May 2017 14:44:36 +0200
Fredrik Markstrom <fredrik.markstrom@gmail.com> wrote:

> Currently veth drops all packets larger then the mtu set on the receiving
> end of the pair. This is inconsistent with most hardware ethernet drivers.

There is no guarantee that packets larger than MTU + VLAN tag will be received
by hardware drivers. So why is this necessary for veth? What is your special
use case which makes this necessary?

Re: [PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[David Miller]

From: Fredrik Markstrom <fredrik.markstrom@gmail.com>
Date: Tue,  9 May 2017 14:44:36 +0200

> Currently veth drops all packets larger then the mtu set on the
> receiving end of the pair. This is inconsistent with most hardware
> ethernet drivers.

False.

In fact, many pieces of ethernet hardware a not physically capable of
sending even VLAN packets that are above the normal base ethernet MTU.

It is therefore untenable to remove this restriction univerally like
this.

Re: [PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[Fredrik Markström]

[-- Attachment #1: Type: text/plain, Size: 2189 bytes --]

On Tue, May 9, 2017 at 7:48 PM, David Miller <davem@davemloft.net> wrote:
>
> From: Fredrik Markstrom <fredrik.markstrom@gmail.com>
> Date: Tue,  9 May 2017 14:44:36 +0200
>
> > Currently veth drops all packets larger then the mtu set on the
> > receiving end of the pair. This is inconsistent with most hardware
> > ethernet drivers.
>
> False.
>
> In fact, many pieces of ethernet hardware a not physically capable of
> sending even VLAN packets that are above the normal base ethernet MTU.
>

Maybe I was unclear, the veth implementation drops all packers larger then
the
configured MTU (on the receiving interface).
Most ethernet drivers accepts packets up to the ethernet MTU no matter the
configured MTU. As far as I can tell from the RFC:s that is ok.

A simpler solution would be to only drop packets larger then ethernet MTU
(like
most network drivers), but I guess that will break existing stuff already
out there.

The example below demonstrates what behaviour I'm referring to.

Example:
---- 8< ------
# veth0 and veth1 is a veth pair and veth1 has ben moved to a separate
network namespace.
% # NS A
% ip address add 1.2.3.4/24 dev veth0
% ip link set veth0 mtu 300 up

% # NS B
% ip address add 1.2.3.5/24 dev veth1
% ip link set veth1 mtu 1000 up
% ping -c 1 -W 1 -s 400 1.2.3.4
PING 1.2.3.4 (1.2.3.4) 400(428) bytes of data.

--- 1.2.3.4 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms
---- 8< ------

While it works fine in most setup:s with hw-interfaces:

---- 8< ------
# Host A eth2 and Host B eth0 is on the same network.

# On HOST A
% ip address add 1.2.3.4/24 dev eth2
% ip link set eth2 mtu 300 up

% # HOST B
% ip address add 1.2.3.5/24 dev eth0
% ip link set eth0 mtu 1000 up
% ping -c 1 -W 1 -s 400 1.2.3.4
PING 1.2.3.4 (1.2.3.4) 400(428) bytes of data.
408 bytes from 1.2.3.4: icmp_seq=1 ttl=64 time=1.57 ms

--- 1.2.3.4 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.573/1.573/1.573/0.000 ms
---- 8< ------

>
> It is therefore untenable to remove this restriction univerally like
> this.

With the explaination above, do you still think it's untenable ?

/Fredrik

[-- Attachment #2: Type: text/html, Size: 2759 bytes --]

Re: [PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[Fredrik Markström]

On Tue, May 9, 2017 at 7:48 PM, David Miller <davem@davemloft.net> wrote:
>
> From: Fredrik Markstrom <fredrik.markstrom@gmail.com>
> Date: Tue,  9 May 2017 14:44:36 +0200
>
> > Currently veth drops all packets larger then the mtu set on the
> > receiving end of the pair. This is inconsistent with most hardware
> > ethernet drivers.
>
> False.
>
> In fact, many pieces of ethernet hardware a not physically capable of
> sending even VLAN packets that are above the normal base ethernet MTU.
>

Maybe I was unclear, the veth implementation drops all packers larger then the
configured MTU (on the receiving interface).
Most ethernet drivers accepts packets up to the ethernet MTU no matter the
configured MTU. As far as I can tell from the RFC:s that is ok.

A simpler solution would be to only drop packets larger then ethernet MTU (like
most network drivers), but I guess that will break existing stuff
already out there.

The example below demonstrates what behaviour I'm referring to.

Example:
---- 8< ------
# veth0 and veth1 is a veth pair and veth1 has ben moved to a separate
network namespace.
% # NS A
% ip address add 1.2.3.4/24 dev veth0
% ip link set veth0 mtu 300 up

% # NS B
% ip address add 1.2.3.5/24 dev veth1
% ip link set veth1 mtu 1000 up
% ping -c 1 -W 1 -s 400 1.2.3.4
PING 1.2.3.4 (1.2.3.4) 400(428) bytes of data.

--- 1.2.3.4 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms
---- 8< ------

While it works fine in most setup:s with hw-interfaces:

---- 8< ------
# Host A eth2 and Host B eth0 is on the same network.

# On HOST A
% ip address add 1.2.3.4/24 dev eth2
% ip link set eth2 mtu 300 up

% # HOST B
% ip address add 1.2.3.5/24 dev eth0
% ip link set eth0 mtu 1000 up
% ping -c 1 -W 1 -s 400 1.2.3.4
PING 1.2.3.4 (1.2.3.4) 400(428) bytes of data.
408 bytes from 1.2.3.4: icmp_seq=1 ttl=64 time=1.57 ms

--- 1.2.3.4 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.573/1.573/1.573/0.000 ms
---- 8< ------

>
> It is therefore untenable to remove this restriction univerally like
> this.

With the explaination above, do you still think it's untenable ?

/Fredrik

Re: [PATCH 0/2] net: Set maximum receive packet size on veth interfaces

[Cong Wang]

On Tue, May 9, 2017 at 5:42 PM, Fredrik Markström
<fredrik.markstrom@gmail.com> wrote:
>
> Maybe I was unclear, the veth implementation drops all packers larger then the
> configured MTU (on the receiving interface).
> Most ethernet drivers accepts packets up to the ethernet MTU no matter the
> configured MTU. As far as I can tell from the RFC:s that is ok.

This is because IP layer does the fragmentation for you. But some drivers,
for example tg3, drop packet larger than its dev->mtu very early too.

>
> A simpler solution would be to only drop packets larger then ethernet MTU (like
> most network drivers), but I guess that will break existing stuff
> already out there.

I wonder why did we introduce that mtu check for veth when IP layer
could either fragment or reject with ICMP?