[PATCH V2 net-next 1/6] virtio: Add support for SCTP checksum offloading

[PATCH V2 net-next 1/6] virtio: Add support for SCTP checksum offloading

[Vladislav Yasevich]

To support SCTP checksum offloading, we need to add a new feature
to virtio_net, so we can negotiate support between the hypervisor
and the guest.
The HOST feature bit signifies offloading support for transmit and
enables device offload features.
The GUEST feature bit signifies offloading support of recieve and
is currently only used by the driver in case of xdp.  

That patch also adds an addition virtio_net header flag which
mirrors the skb->csum_not_inet flag.  This flags is used to indicate
that is this an SCTP packet that needs its checksum computed by the
lower layer.  In this case, the lower layer is the host hypervisor or
possibly HW nic that supporst CRC32c offload.

In the case that GUEST feature bit is flag, it will be possible to
receive a virtio_net header with this bit set, which will set the
corresponding skb bit.  SCTP protocol will be updated to correctly
deal with it.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
 drivers/net/virtio_net.c        | 14 +++++++++++++-
 include/linux/virtio_net.h      |  6 ++++++
 include/uapi/linux/virtio_net.h |  5 +++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7b187ec..34af280 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2148,6 +2148,8 @@ static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
 
 	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
 		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
+		offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
 
 	return virtnet_set_guest_offloads(vi, offloads);
 }
@@ -2160,6 +2162,8 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
 		return 0;
 	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
 		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
+		offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
 
 	return virtnet_set_guest_offloads(vi, offloads);
 }
@@ -2724,6 +2728,7 @@ static int virtnet_probe(struct virtio_device *vdev)
 	/* Do we support "hardware" checksums? */
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
 		/* This opens up the world of extra features. */
+
 		dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_SG;
 		if (csum)
 			dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG;
@@ -2746,9 +2751,15 @@ static int virtnet_probe(struct virtio_device *vdev)
 			dev->features |= dev->hw_features & NETIF_F_ALL_TSO;
 		/* (!csum && gso) case will be fixed by register_netdev() */
 	}
+
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
 		dev->features |= NETIF_F_RXCSUM;
 
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_SCTP_CSUM)) {
+		dev->hw_features |= NETIF_F_SCTP_CRC;
+		dev->features |= NETIF_F_SCTP_CRC;
+	}
+
 	dev->vlan_features = dev->features;
 
 	/* MTU range: 68 - 65535 */
@@ -2962,7 +2973,8 @@ static struct virtio_device_id id_table[] = {
 	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
 	VIRTIO_NET_F_CTRL_MAC_ADDR, \
 	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
-	VIRTIO_NET_F_SPEED_DUPLEX
+	VIRTIO_NET_F_SPEED_DUPLEX, \
+	VIRTIO_NET_F_HOST_SCTP_CSUM, VIRTIO_NET_F_GUEST_SCTP_CSUM
 
 static unsigned int features[] = {
 	VIRTNET_FEATURES,
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index f144216..28fffdc 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -39,6 +39,9 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
 
 		if (!skb_partial_csum_set(skb, start, off))
 			return -EINVAL;
+
+		if (hdr->flags & VIRTIO_NET_HDR_F_CSUM_NOT_INET)
+			skb->csum_not_inet = 1;
 	}
 
 	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
@@ -91,6 +94,9 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
 				skb_checksum_start_offset(skb));
 		hdr->csum_offset = __cpu_to_virtio16(little_endian,
 				skb->csum_offset);
+
+		if (skb->csum_not_inet)
+			hdr->flags |= VIRTIO_NET_HDR_F_CSUM_NOT_INET;
 	} else if (has_data_valid &&
 		   skb->ip_summed == CHECKSUM_UNNECESSARY) {
 		hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 5de6ed3..9dfca1a 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -57,6 +57,10 @@
 					 * Steering */
 #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
 
+#define VIRTIO_NET_F_GUEST_SCTP_CSUM  61 /* Guest handles SCTP pks w/ partial
+					  * csum */
+#define VIRTIO_NET_F_HOST_SCTP_CSUM   62 /* HOST handles SCTP pkts w/ partial
+					  * csum */
 #define VIRTIO_NET_F_SPEED_DUPLEX 63	/* Device set linkspeed and duplex */
 
 #ifndef VIRTIO_NET_NO_LEGACY
@@ -101,6 +105,7 @@ struct virtio_net_config {
 struct virtio_net_hdr_v1 {
 #define VIRTIO_NET_HDR_F_NEEDS_CSUM	1	/* Use csum_start, csum_offset */
 #define VIRTIO_NET_HDR_F_DATA_VALID	2	/* Csum is valid */
+#define VIRTIO_NET_HDR_F_CSUM_NOT_INET  4       /* Checksum is not inet */
 	__u8 flags;
 #define VIRTIO_NET_HDR_GSO_NONE		0	/* Not a GSO frame */
 #define VIRTIO_NET_HDR_GSO_TCPV4	1	/* GSO frame, IPv4 TCP (TSO) */
-- 
2.9.5

[PATCH V2 net-next 2/6] sctp: Handle sctp packets with CHECKSUM_PARTIAL

[Vladislav Yasevich]

With SCTP checksum offload available in virtio, it is now
possible for virtio to receive a sctp packet with CHECKSUM_PARTIAL
set (guest-to-guest traffic).  SCTP doesn't really have a
partial checksum like TCP does, because CRC32c can't do partial
additive checksumming.  It's all or nothing.  So an SCTP packet
with CHECKSUM_PARTIAL will have checksum set to 0.  Let SCTP
treat this as a valid checksum if CHECKSUM_PARTIAL is set.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
 net/sctp/input.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/sctp/input.c b/net/sctp/input.c
index ba8a6e6..055b8ffa 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -80,8 +80,17 @@ static inline int sctp_rcv_checksum(struct net *net, struct sk_buff *skb)
 {
 	struct sctphdr *sh = sctp_hdr(skb);
 	__le32 cmp = sh->checksum;
-	__le32 val = sctp_compute_cksum(skb, 0);
+	__le32 val = 0;
 
+	/* In sctp PARTIAL checksum is always 0.  This is a case of
+	 * a packet received from guest that supports checksum offload.
+	 * Assume it's correct as there is really no way to verify,
+	 * and we want to avaoid computing it unnecesarily.
+	 */
+	if (skb->ip_summed == CHECKSUM_PARTIAL)
+		return 0;
+
+	val = sctp_compute_cksum(skb, 0);
 	if (val != cmp) {
 		/* CRC failure, dump it. */
 		__SCTP_INC_STATS(net, SCTP_MIB_CHECKSUMERRORS);
-- 
2.9.5

[PATCH V2 net-next 3/6] sctp: Build sctp offload support into the base kernel

[Vladislav Yasevich]

With the SCTP checksum offload support added to virtio, it is
now possible to get into a situation where SCTP not present
in the kernel, but the feature is negotiated.  Handle this just
like we do IPv6 and other modular offloads.
Move the sctp offload out of the sctp module and into the base
kernel.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
 include/net/sctp/sctp.h | 5 -----
 net/Kconfig             | 1 +
 net/sctp/Kconfig        | 1 -
 net/sctp/Makefile       | 3 ++-
 net/sctp/offload.c      | 4 +++-
 net/sctp/protocol.c     | 3 ---
 6 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index 72c5b8f..625b45f 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -183,11 +183,6 @@ struct sctp_transport *sctp_epaddr_lookup_transport(
 int __net_init sctp_proc_init(struct net *net);
 
 /*
- * sctp/offload.c
- */
-int sctp_offload_init(void);
-
-/*
  * sctp/stream_sched.c
  */
 void sctp_sched_ops_init(void);
diff --git a/net/Kconfig b/net/Kconfig
index 0428f12..2773f98 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -64,6 +64,7 @@ config INET
 	bool "TCP/IP networking"
 	select CRYPTO
 	select CRYPTO_AES
+	select LIBCRC32C
 	---help---
 	  These are the protocols used on the Internet and on most local
 	  Ethernets. It is highly recommended to say Y here (this will enlarge
diff --git a/net/sctp/Kconfig b/net/sctp/Kconfig
index c740b18..d07477a 100644
--- a/net/sctp/Kconfig
+++ b/net/sctp/Kconfig
@@ -9,7 +9,6 @@ menuconfig IP_SCTP
 	select CRYPTO
 	select CRYPTO_HMAC
 	select CRYPTO_SHA1
-	select LIBCRC32C
 	---help---
 	  Stream Control Transmission Protocol
 
diff --git a/net/sctp/Makefile b/net/sctp/Makefile
index e845e45..ee206ca 100644
--- a/net/sctp/Makefile
+++ b/net/sctp/Makefile
@@ -5,6 +5,7 @@
 
 obj-$(CONFIG_IP_SCTP) += sctp.o
 obj-$(CONFIG_INET_SCTP_DIAG) += sctp_diag.o
+obj-$(CONFIG_INET) += offload.o
 
 sctp-y := sm_statetable.o sm_statefuns.o sm_sideeffect.o \
 	  protocol.o endpointola.o associola.o \
@@ -12,7 +13,7 @@ sctp-y := sm_statetable.o sm_statefuns.o sm_sideeffect.o \
 	  inqueue.o outqueue.o ulpqueue.o \
 	  tsnmap.o bind_addr.o socket.o primitive.o \
 	  output.o input.o debug.o stream.o auth.o \
-	  offload.o stream_sched.o stream_sched_prio.o \
+	  stream_sched.o stream_sched_prio.o \
 	  stream_sched_rr.o stream_interleave.o
 
 sctp_diag-y := diag.o
diff --git a/net/sctp/offload.c b/net/sctp/offload.c
index 123e9f2..c61cbde 100644
--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -107,7 +107,7 @@ static const struct skb_checksum_ops crc32c_csum_ops = {
 	.combine = sctp_csum_combine,
 };
 
-int __init sctp_offload_init(void)
+static int __init sctp_offload_init(void)
 {
 	int ret;
 
@@ -127,3 +127,5 @@ int __init sctp_offload_init(void)
 out:
 	return ret;
 }
+
+fs_initcall(sctp_offload_init);
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index a24cde2..46d2b63 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1479,9 +1479,6 @@ static __init int sctp_init(void)
 	if (status)
 		goto err_v6_add_protocol;
 
-	if (sctp_offload_init() < 0)
-		pr_crit("%s: Cannot add SCTP protocol offload\n", __func__);
-
 out:
 	return status;
 err_v6_add_protocol:
-- 
2.9.5

[PATCH V2 net-next 4/6] tun: Add support for SCTP checksum offload

[Vladislav Yasevich]

Adds a new tun offload flag to allow for SCTP checksum offload.
The flag has to be set by the user and defaults to "no offload".
Add SCTP checksum support to the supported tun features.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
 drivers/net/tun.c           | 7 ++++++-
 include/uapi/linux/if_tun.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a1ba262..4f314a6 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -216,7 +216,7 @@ struct tun_struct {
 	struct net_device	*dev;
 	netdev_features_t	set_features;
 #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
-			  NETIF_F_TSO6)
+			  NETIF_F_TSO6|NETIF_F_SCTP_CRC)
 
 	int			align;
 	int			vnet_hdr_sz;
@@ -2719,6 +2719,11 @@ static int set_offload(struct tun_struct *tun, unsigned long arg)
 		arg &= ~TUN_F_UFO;
 	}
 
+	if (arg & TUN_F_SCTP_CSUM) {
+		features |= NETIF_F_SCTP_CRC;
+		arg &= ~TUN_F_SCTP_CSUM;
+	}
+
 	/* This gives the user a way to test for new features in future by
 	 * trying to set them. */
 	if (arg)
diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
index ee432cd..061aea8 100644
--- a/include/uapi/linux/if_tun.h
+++ b/include/uapi/linux/if_tun.h
@@ -86,6 +86,7 @@
 #define TUN_F_TSO6	0x04	/* I can handle TSO for IPv6 packets */
 #define TUN_F_TSO_ECN	0x08	/* I can handle TSO with ECN bits. */
 #define TUN_F_UFO	0x10	/* I can handle UFO packets */
+#define TUN_F_SCTP_CSUM 0x20	/* I can handle SCTP checksums offloads */
 
 /* Protocol info prepended to the packets (when IFF_NO_PI is not set) */
 #define TUN_PKT_STRIP	0x0001
-- 
2.9.5

[PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Vladislav Yasevich]

Since we now have support for software CRC32c offload, turn it on
for macvlan and macvtap devices so that guests can take advantage
of offload SCTP checksums to the host or host hardware.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
 drivers/net/macvlan.c | 5 +++--
 drivers/net/tap.c     | 8 +++++---
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 725f4b4..646b730 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
 
 #define ALWAYS_ON_OFFLOADS \
 	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
-	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
+	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
 
 #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
 
@@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
 	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
 	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
 	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
-	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
+	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
+	 NETIF_F_SCTP_CRC)
 
 #define MACVLAN_STATE_MASK \
 	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 9b6cb78..2c8512b 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
 		 *	  check, we either support them all or none.
 		 */
 		if (skb->ip_summed == CHECKSUM_PARTIAL &&
-		    !(features & NETIF_F_CSUM_MASK) &&
-		    skb_checksum_help(skb))
+		    skb_csum_hwoffload_help(skb, features))
 			goto drop;
 		if (ptr_ring_produce(&q->ring, skb))
 			goto drop;
@@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
 		}
 	}
 
+	if (arg & TUN_F_SCTP_CSUM)
+		feature_mask |= NETIF_F_SCTP_CRC;
+
 	/* tun/tap driver inverts the usage for TSO offloads, where
 	 * setting the TSO bit means that the userspace wants to
 	 * accept TSO frames and turning it off means that user space
@@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
 	case TUNSETOFFLOAD:
 		/* let the user check for future flags */
 		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
-			    TUN_F_TSO_ECN | TUN_F_UFO))
+			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
 			return -EINVAL;
 
 		rtnl_lock();
-- 
2.9.5

[PATCH V2 net-next 6/6] ipvlan: Add support for SCTP checksum offload

[Vladislav Yasevich]

Since ipvlan is a software device, we can turn on SCTP checksum
offload and let the checksum be computed at the lower layer.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
 drivers/net/ipvlan/ipvlan_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 450eec2..ddb1590 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -161,7 +161,8 @@ static void ipvlan_port_destroy(struct net_device *dev)
 	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
 	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_GSO_ROBUST | \
 	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
-	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
+	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
+	 NETIF_F_SCTP_CRC)
 
 #define IPVLAN_STATE_MASK \
 	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
-- 
2.9.5

Re: [PATCH V2 net-next 1/6] virtio: Add support for SCTP checksum offloading

[Michael S. Tsirkin]

On Tue, May 01, 2018 at 10:07:34PM -0400, Vladislav Yasevich wrote:
> To support SCTP checksum offloading, we need to add a new feature
> to virtio_net, so we can negotiate support between the hypervisor
> and the guest.
> The HOST feature bit signifies offloading support for transmit and
> enables device offload features.
> The GUEST feature bit signifies offloading support of recieve and
> is currently only used by the driver in case of xdp.  
> 
> That patch also adds an addition virtio_net header flag which
> mirrors the skb->csum_not_inet flag.  This flags is used to indicate
> that is this an SCTP packet that needs its checksum computed by the
> lower layer.  In this case, the lower layer is the host hypervisor or
> possibly HW nic that supporst CRC32c offload.
> 
> In the case that GUEST feature bit is flag, it will be possible to
> receive a virtio_net header with this bit set, which will set the
> corresponding skb bit.  SCTP protocol will be updated to correctly
> deal with it.
> 
> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> ---
>  drivers/net/virtio_net.c        | 14 +++++++++++++-
>  include/linux/virtio_net.h      |  6 ++++++
>  include/uapi/linux/virtio_net.h |  5 +++++
>  3 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7b187ec..34af280 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2148,6 +2148,8 @@ static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
>  
>  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
>  		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
> +		offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
>  
>  	return virtnet_set_guest_offloads(vi, offloads);
>  }
> @@ -2160,6 +2162,8 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
>  		return 0;
>  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
>  		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
> +		offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
>  
>  	return virtnet_set_guest_offloads(vi, offloads);
>  }
> @@ -2724,6 +2728,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	/* Do we support "hardware" checksums? */
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
>  		/* This opens up the world of extra features. */
> +
>  		dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_SG;
>  		if (csum)
>  			dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG;
> @@ -2746,9 +2751,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>  			dev->features |= dev->hw_features & NETIF_F_ALL_TSO;
>  		/* (!csum && gso) case will be fixed by register_netdev() */
>  	}
> +
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
>  		dev->features |= NETIF_F_RXCSUM;
>  
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_SCTP_CSUM)) {
> +		dev->hw_features |= NETIF_F_SCTP_CRC;
> +		dev->features |= NETIF_F_SCTP_CRC;
> +	}
> +
>  	dev->vlan_features = dev->features;
>  
>  	/* MTU range: 68 - 65535 */
> @@ -2962,7 +2973,8 @@ static struct virtio_device_id id_table[] = {
>  	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
>  	VIRTIO_NET_F_CTRL_MAC_ADDR, \
>  	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> -	VIRTIO_NET_F_SPEED_DUPLEX
> +	VIRTIO_NET_F_SPEED_DUPLEX, \
> +	VIRTIO_NET_F_HOST_SCTP_CSUM, VIRTIO_NET_F_GUEST_SCTP_CSUM
>  
>  static unsigned int features[] = {
>  	VIRTNET_FEATURES,
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index f144216..28fffdc 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -39,6 +39,9 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
>  
>  		if (!skb_partial_csum_set(skb, start, off))
>  			return -EINVAL;
> +
> +		if (hdr->flags & VIRTIO_NET_HDR_F_CSUM_NOT_INET)
> +			skb->csum_not_inet = 1;
>  	}
>  
>  	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
> @@ -91,6 +94,9 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
>  				skb_checksum_start_offset(skb));
>  		hdr->csum_offset = __cpu_to_virtio16(little_endian,
>  				skb->csum_offset);
> +
> +		if (skb->csum_not_inet)
> +			hdr->flags |= VIRTIO_NET_HDR_F_CSUM_NOT_INET;
>  	} else if (has_data_valid &&
>  		   skb->ip_summed == CHECKSUM_UNNECESSARY) {
>  		hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index 5de6ed3..9dfca1a 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -57,6 +57,10 @@
>  					 * Steering */
>  #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
>  
> +#define VIRTIO_NET_F_GUEST_SCTP_CSUM  61 /* Guest handles SCTP pks w/ partial
> +					  * csum */
> +#define VIRTIO_NET_F_HOST_SCTP_CSUM   62 /* HOST handles SCTP pkts w/ partial
> +					  * csum */
>  #define VIRTIO_NET_F_SPEED_DUPLEX 63	/* Device set linkspeed and duplex */
>  
>  #ifndef VIRTIO_NET_NO_LEGACY
> @@ -101,6 +105,7 @@ struct virtio_net_config {
>  struct virtio_net_hdr_v1 {
>  #define VIRTIO_NET_HDR_F_NEEDS_CSUM	1	/* Use csum_start, csum_offset */
>  #define VIRTIO_NET_HDR_F_DATA_VALID	2	/* Csum is valid */
> +#define VIRTIO_NET_HDR_F_CSUM_NOT_INET  4       /* Checksum is not inet */

Both comment and name are not very informative.
How about just saying CRC32c ?

>  	__u8 flags;
>  #define VIRTIO_NET_HDR_GSO_NONE		0	/* Not a GSO frame */
>  #define VIRTIO_NET_HDR_GSO_TCPV4	1	/* GSO frame, IPv4 TCP (TSO) */
> -- 
> 2.9.5

Re: [PATCH V2 net-next 1/6] virtio: Add support for SCTP checksum offloading

[Michael S. Tsirkin]

On Wed, May 02, 2018 at 11:14:13AM -0300, Marcelo Ricardo Leitner wrote:
> On Wed, May 02, 2018 at 06:16:45AM +0300, Michael S. Tsirkin wrote:
> > On Tue, May 01, 2018 at 10:07:34PM -0400, Vladislav Yasevich wrote:
> > > To support SCTP checksum offloading, we need to add a new feature
> > > to virtio_net, so we can negotiate support between the hypervisor
> > > and the guest.
> > > The HOST feature bit signifies offloading support for transmit and
> > > enables device offload features.
> > > The GUEST feature bit signifies offloading support of recieve and
> > > is currently only used by the driver in case of xdp.
> > >
> > > That patch also adds an addition virtio_net header flag which
> > > mirrors the skb->csum_not_inet flag.  This flags is used to indicate
> > > that is this an SCTP packet that needs its checksum computed by the
> > > lower layer.  In this case, the lower layer is the host hypervisor or
> > > possibly HW nic that supporst CRC32c offload.
> > >
> > > In the case that GUEST feature bit is flag, it will be possible to
> > > receive a virtio_net header with this bit set, which will set the
> > > corresponding skb bit.  SCTP protocol will be updated to correctly
> > > deal with it.
> > >
> > > Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> > > ---
> > >  drivers/net/virtio_net.c        | 14 +++++++++++++-
> > >  include/linux/virtio_net.h      |  6 ++++++
> > >  include/uapi/linux/virtio_net.h |  5 +++++
> > >  3 files changed, 24 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 7b187ec..34af280 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -2148,6 +2148,8 @@ static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
> > >
> > >  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> > >  		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> > > +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
> > > +		offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
> > >
> > >  	return virtnet_set_guest_offloads(vi, offloads);
> > >  }
> > > @@ -2160,6 +2162,8 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
> > >  		return 0;
> > >  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> > >  		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> > > +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
> > > +		offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
> > >
> > >  	return virtnet_set_guest_offloads(vi, offloads);
> > >  }
> > > @@ -2724,6 +2728,7 @@ static int virtnet_probe(struct virtio_device *vdev)
> > >  	/* Do we support "hardware" checksums? */
> > >  	if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
> > >  		/* This opens up the world of extra features. */
> > > +
> > >  		dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_SG;
> > >  		if (csum)
> > >  			dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG;
> > > @@ -2746,9 +2751,15 @@ static int virtnet_probe(struct virtio_device *vdev)
> > >  			dev->features |= dev->hw_features & NETIF_F_ALL_TSO;
> > >  		/* (!csum && gso) case will be fixed by register_netdev() */
> > >  	}
> > > +
> > >  	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
> > >  		dev->features |= NETIF_F_RXCSUM;
> > >
> > > +	if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_SCTP_CSUM)) {
> > > +		dev->hw_features |= NETIF_F_SCTP_CRC;
> > > +		dev->features |= NETIF_F_SCTP_CRC;
> > > +	}
> > > +
> > >  	dev->vlan_features = dev->features;
> > >
> > >  	/* MTU range: 68 - 65535 */
> > > @@ -2962,7 +2973,8 @@ static struct virtio_device_id id_table[] = {
> > >  	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
> > >  	VIRTIO_NET_F_CTRL_MAC_ADDR, \
> > >  	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> > > -	VIRTIO_NET_F_SPEED_DUPLEX
> > > +	VIRTIO_NET_F_SPEED_DUPLEX, \
> > > +	VIRTIO_NET_F_HOST_SCTP_CSUM, VIRTIO_NET_F_GUEST_SCTP_CSUM
> > >
> > >  static unsigned int features[] = {
> > >  	VIRTNET_FEATURES,
> > > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> > > index f144216..28fffdc 100644
> > > --- a/include/linux/virtio_net.h
> > > +++ b/include/linux/virtio_net.h
> > > @@ -39,6 +39,9 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
> > >
> > >  		if (!skb_partial_csum_set(skb, start, off))
> > >  			return -EINVAL;
> > > +
> > > +		if (hdr->flags & VIRTIO_NET_HDR_F_CSUM_NOT_INET)
> > > +			skb->csum_not_inet = 1;
> > >  	}
> > >
> > >  	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
> > > @@ -91,6 +94,9 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
> > >  				skb_checksum_start_offset(skb));
> > >  		hdr->csum_offset = __cpu_to_virtio16(little_endian,
> > >  				skb->csum_offset);
> > > +
> > > +		if (skb->csum_not_inet)
> > > +			hdr->flags |= VIRTIO_NET_HDR_F_CSUM_NOT_INET;
> > >  	} else if (has_data_valid &&
> > >  		   skb->ip_summed == CHECKSUM_UNNECESSARY) {
> > >  		hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
> > > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> > > index 5de6ed3..9dfca1a 100644
> > > --- a/include/uapi/linux/virtio_net.h
> > > +++ b/include/uapi/linux/virtio_net.h
> > > @@ -57,6 +57,10 @@
> > >  					 * Steering */
> > >  #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
> > >
> > > +#define VIRTIO_NET_F_GUEST_SCTP_CSUM  61 /* Guest handles SCTP pks w/ partial
> > > +					  * csum */
> > > +#define VIRTIO_NET_F_HOST_SCTP_CSUM   62 /* HOST handles SCTP pkts w/ partial
> > > +					  * csum */
> > >  #define VIRTIO_NET_F_SPEED_DUPLEX 63	/* Device set linkspeed and duplex */
> > >
> > >  #ifndef VIRTIO_NET_NO_LEGACY
> > > @@ -101,6 +105,7 @@ struct virtio_net_config {
> > >  struct virtio_net_hdr_v1 {
> > >  #define VIRTIO_NET_HDR_F_NEEDS_CSUM	1	/* Use csum_start, csum_offset */
> > >  #define VIRTIO_NET_HDR_F_DATA_VALID	2	/* Csum is valid */
> > > +#define VIRTIO_NET_HDR_F_CSUM_NOT_INET  4       /* Checksum is not inet */
> >
> > Both comment and name are not very informative.
> > How about just saying CRC32c ?
> 
> csum_not_inet is following the nomenclature used in sk_buff. Initially
> Davide had named the sk_buff field after crc32c but then it was argued
> that maybe another check method may be introduced later and the name
> would be bogus, thus why the "csum_not_inet".

That's sk_buff internals, since Linux can change these
at any time without breaking anything.

virtio defines an ABI so we won't be able to make it
mean something else, need to document it fully.
"Go read linux net core code" is not a good answer
to the natural question "what does this bit in the
interface do".

> >
> > >  	__u8 flags;
> > >  #define VIRTIO_NET_HDR_GSO_NONE		0	/* Not a GSO frame */
> > >  #define VIRTIO_NET_HDR_GSO_TCPV4	1	/* GSO frame, IPv4 TCP (TSO) */
> > > --
> > > 2.9.5
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >

Re: [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Michael S. Tsirkin]

On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
> Since we now have support for software CRC32c offload, turn it on
> for macvlan and macvtap devices so that guests can take advantage
> of offload SCTP checksums to the host or host hardware.
> 
> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> ---
>  drivers/net/macvlan.c | 5 +++--
>  drivers/net/tap.c     | 8 +++++---
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 725f4b4..646b730 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>  
>  #define ALWAYS_ON_OFFLOADS \
>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
>  
>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
>  
> @@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
> +	 NETIF_F_SCTP_CRC)
>  
>  #define MACVLAN_STATE_MASK \
>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> index 9b6cb78..2c8512b 100644
> --- a/drivers/net/tap.c
> +++ b/drivers/net/tap.c
> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
>  		 *	  check, we either support them all or none.
>  		 */
>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
> -		    !(features & NETIF_F_CSUM_MASK) &&
> -		    skb_checksum_help(skb))
> +		    skb_csum_hwoffload_help(skb, features))
>  			goto drop;
>  		if (ptr_ring_produce(&q->ring, skb))
>  			goto drop;
> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
>  		}
>  	}
>  
> +	if (arg & TUN_F_SCTP_CSUM)
> +		feature_mask |= NETIF_F_SCTP_CRC;
> +

so this still affects TX, shouldn't this affect RX instead?


>  	/* tun/tap driver inverts the usage for TSO offloads, where
>  	 * setting the TSO bit means that the userspace wants to
>  	 * accept TSO frames and turning it off means that user space
> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
>  	case TUNSETOFFLOAD:
>  		/* let the user check for future flags */
>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> -			    TUN_F_TSO_ECN | TUN_F_UFO))
> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
>  			return -EINVAL;
>  
>  		rtnl_lock();
> -- 
> 2.9.5

Re: [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Vlad Yasevich]

On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
> On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
>> Since we now have support for software CRC32c offload, turn it on
>> for macvlan and macvtap devices so that guests can take advantage
>> of offload SCTP checksums to the host or host hardware.
>>
>> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
>> ---
>>  drivers/net/macvlan.c | 5 +++--
>>  drivers/net/tap.c     | 8 +++++---
>>  2 files changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
>> index 725f4b4..646b730 100644
>> --- a/drivers/net/macvlan.c
>> +++ b/drivers/net/macvlan.c
>> @@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>>  
>>  #define ALWAYS_ON_OFFLOADS \
>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
>> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
>> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
>>  
>>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
>>  
>> @@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
>>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
>>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
>> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
>> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
>> +	 NETIF_F_SCTP_CRC)
>>  
>>  #define MACVLAN_STATE_MASK \
>>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
>> index 9b6cb78..2c8512b 100644
>> --- a/drivers/net/tap.c
>> +++ b/drivers/net/tap.c
>> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
>>  		 *	  check, we either support them all or none.
>>  		 */
>>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
>> -		    !(features & NETIF_F_CSUM_MASK) &&
>> -		    skb_checksum_help(skb))
>> +		    skb_csum_hwoffload_help(skb, features))
>>  			goto drop;
>>  		if (ptr_ring_produce(&q->ring, skb))
>>  			goto drop;
>> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
>>  		}
>>  	}
>>  
>> +	if (arg & TUN_F_SCTP_CSUM)
>> +		feature_mask |= NETIF_F_SCTP_CRC;
>> +
> 
> so this still affects TX, shouldn't this affect RX instead?

There is no bit to set on the RX path just like there is no bit to set on the RX patch
for TUN_F_CSUM.

We only invert TSO offloads, not checksum offloads as the comment below states.
For checksum,  macvtap has to compute the checksum itself in tap_handle_frame() above.
It uses tx feature bits to see if needs do to the checksum.

If you think we need another flag to macvtap to control RXCSUM, that would need to be
separate and cover standard TCP checksum as well.

-vlad

> 
> 
>>  	/* tun/tap driver inverts the usage for TSO offloads, where
>>  	 * setting the TSO bit means that the userspace wants to
>>  	 * accept TSO frames and turning it off means that user space
>> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
>>  	case TUNSETOFFLOAD:
>>  		/* let the user check for future flags */
>>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
>> -			    TUN_F_TSO_ECN | TUN_F_UFO))
>> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
>>  			return -EINVAL;
>>  
>>  		rtnl_lock();
>> -- 
>> 2.9.5

Re: [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Michael S. Tsirkin]

On Wed, May 02, 2018 at 09:27:00AM -0400, Vlad Yasevich wrote:
> On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
> > On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
> >> Since we now have support for software CRC32c offload, turn it on
> >> for macvlan and macvtap devices so that guests can take advantage
> >> of offload SCTP checksums to the host or host hardware.
> >>
> >> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> >> ---
> >>  drivers/net/macvlan.c | 5 +++--
> >>  drivers/net/tap.c     | 8 +++++---
> >>  2 files changed, 8 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> >> index 725f4b4..646b730 100644
> >> --- a/drivers/net/macvlan.c
> >> +++ b/drivers/net/macvlan.c
> >> @@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
> >>  
> >>  #define ALWAYS_ON_OFFLOADS \
> >>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
> >> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
> >> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
> >>  
> >>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
> >>  
> >> @@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
> >>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
> >>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
> >>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
> >> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
> >> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
> >> +	 NETIF_F_SCTP_CRC)
> >>  
> >>  #define MACVLAN_STATE_MASK \
> >>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
> >> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> >> index 9b6cb78..2c8512b 100644
> >> --- a/drivers/net/tap.c
> >> +++ b/drivers/net/tap.c
> >> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
> >>  		 *	  check, we either support them all or none.
> >>  		 */
> >>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
> >> -		    !(features & NETIF_F_CSUM_MASK) &&
> >> -		    skb_checksum_help(skb))
> >> +		    skb_csum_hwoffload_help(skb, features))
> >>  			goto drop;
> >>  		if (ptr_ring_produce(&q->ring, skb))
> >>  			goto drop;
> >> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
> >>  		}
> >>  	}
> >>  
> >> +	if (arg & TUN_F_SCTP_CSUM)
> >> +		feature_mask |= NETIF_F_SCTP_CRC;
> >> +
> > 
> > so this still affects TX, shouldn't this affect RX instead?
> 
> There is no bit to set on the RX path just like there is no bit to set on the RX patch
> for TUN_F_CSUM.
> 
> We only invert TSO offloads, not checksum offloads as the comment below states.
> For checksum,  macvtap has to compute the checksum itself in tap_handle_frame() above.
> It uses tx feature bits to see if needs do to the checksum.
> 
> If you think we need another flag to macvtap to control RXCSUM, that would need to be
> separate and cover standard TCP checksum as well.
> 
> -vlad

Confused. What is the meaning of TUN_F_SCTP_CSUM? I assume this is
a way for userspace to tell tun device: "I can handle
packets without SCTP checksum, pls send them my way".

Now what is the implication for macvtap? And why  are
you setting NETIF_F_SCTP_CRC which is a flag
that affects packets sent by guest to host?


> > 
> > 
> >>  	/* tun/tap driver inverts the usage for TSO offloads, where
> >>  	 * setting the TSO bit means that the userspace wants to
> >>  	 * accept TSO frames and turning it off means that user space
> >> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
> >>  	case TUNSETOFFLOAD:
> >>  		/* let the user check for future flags */
> >>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> >> -			    TUN_F_TSO_ECN | TUN_F_UFO))
> >> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
> >>  			return -EINVAL;
> >>  
> >>  		rtnl_lock();
> >> -- 
> >> 2.9.5

Re: [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Vlad Yasevich]

On 05/02/2018 09:46 AM, Michael S. Tsirkin wrote:
> On Wed, May 02, 2018 at 09:27:00AM -0400, Vlad Yasevich wrote:
>> On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
>>> On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
>>>> Since we now have support for software CRC32c offload, turn it on
>>>> for macvlan and macvtap devices so that guests can take advantage
>>>> of offload SCTP checksums to the host or host hardware.
>>>>
>>>> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
>>>> ---
>>>>  drivers/net/macvlan.c | 5 +++--
>>>>  drivers/net/tap.c     | 8 +++++---
>>>>  2 files changed, 8 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
>>>> index 725f4b4..646b730 100644
>>>> --- a/drivers/net/macvlan.c
>>>> +++ b/drivers/net/macvlan.c
>>>> @@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>>>>  
>>>>  #define ALWAYS_ON_OFFLOADS \
>>>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
>>>> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
>>>> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
>>>>  
>>>>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
>>>>  
>>>> @@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>>>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
>>>>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
>>>>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
>>>> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
>>>> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
>>>> +	 NETIF_F_SCTP_CRC)
>>>>  
>>>>  #define MACVLAN_STATE_MASK \
>>>>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
>>>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
>>>> index 9b6cb78..2c8512b 100644
>>>> --- a/drivers/net/tap.c
>>>> +++ b/drivers/net/tap.c
>>>> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
>>>>  		 *	  check, we either support them all or none.
>>>>  		 */
>>>>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
>>>> -		    !(features & NETIF_F_CSUM_MASK) &&
>>>> -		    skb_checksum_help(skb))
>>>> +		    skb_csum_hwoffload_help(skb, features))
>>>>  			goto drop;
>>>>  		if (ptr_ring_produce(&q->ring, skb))
>>>>  			goto drop;
>>>> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
>>>>  		}
>>>>  	}
>>>>  
>>>> +	if (arg & TUN_F_SCTP_CSUM)
>>>> +		feature_mask |= NETIF_F_SCTP_CRC;
>>>> +
>>>
>>> so this still affects TX, shouldn't this affect RX instead?
>>
>> There is no bit to set on the RX path just like there is no bit to set on the RX patch
>> for TUN_F_CSUM.
>>
>> We only invert TSO offloads, not checksum offloads as the comment below states.
>> For checksum,  macvtap has to compute the checksum itself in tap_handle_frame() above.
>> It uses tx feature bits to see if needs do to the checksum.
>>
>> If you think we need another flag to macvtap to control RXCSUM, that would need to be
>> separate and cover standard TCP checksum as well.
>>
>> -vlad
> 
> Confused. What is the meaning of TUN_F_SCTP_CSUM? I assume this is
> a way for userspace to tell tun device: "I can handle
> packets without SCTP checksum, pls send them my way".

Yes,  just as TUN_F_CSUM means that tun device can handle packets with
partial tcp/udp checksum.

> 
> Now what is the implication for macvtap? 

The implication is exactly the same as for TUN_F_CSUM.  If the
flag is set on the macvtap device, the TX checksum feature is
turned on.

> And why  are
> you setting NETIF_F_SCTP_CRC which is a flag
> that affects packets sent by guest to host?

Mainly its because we are using just 1 flag to control checksum
offloading and we need to be able control both tx and rx paths.

What you are suggesting that we either invert what TUN_F_CSUM
is doing in macvtap case, or have another flag that lets us control
TX and RX paths separately.

Either case, that would be separate work.
-vlad

> 
> 
>>>
>>>
>>>>  	/* tun/tap driver inverts the usage for TSO offloads, where
>>>>  	 * setting the TSO bit means that the userspace wants to
>>>>  	 * accept TSO frames and turning it off means that user space
>>>> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
>>>>  	case TUNSETOFFLOAD:
>>>>  		/* let the user check for future flags */
>>>>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
>>>> -			    TUN_F_TSO_ECN | TUN_F_UFO))
>>>> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
>>>>  			return -EINVAL;
>>>>  
>>>>  		rtnl_lock();
>>>> -- 
>>>> 2.9.5

Re: [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Michael S. Tsirkin]

On Wed, May 02, 2018 at 10:00:14AM -0400, Vlad Yasevich wrote:
> On 05/02/2018 09:46 AM, Michael S. Tsirkin wrote:
> > On Wed, May 02, 2018 at 09:27:00AM -0400, Vlad Yasevich wrote:
> >> On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
> >>> On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
> >>>> Since we now have support for software CRC32c offload, turn it on
> >>>> for macvlan and macvtap devices so that guests can take advantage
> >>>> of offload SCTP checksums to the host or host hardware.
> >>>>
> >>>> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> >>>> ---
> >>>>  drivers/net/macvlan.c | 5 +++--
> >>>>  drivers/net/tap.c     | 8 +++++---
> >>>>  2 files changed, 8 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> >>>> index 725f4b4..646b730 100644
> >>>> --- a/drivers/net/macvlan.c
> >>>> +++ b/drivers/net/macvlan.c
> >>>> @@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
> >>>>  
> >>>>  #define ALWAYS_ON_OFFLOADS \
> >>>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
> >>>> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
> >>>> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
> >>>>  
> >>>>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
> >>>>  
> >>>> @@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
> >>>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
> >>>>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
> >>>>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
> >>>> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
> >>>> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
> >>>> +	 NETIF_F_SCTP_CRC)
> >>>>  
> >>>>  #define MACVLAN_STATE_MASK \
> >>>>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
> >>>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> >>>> index 9b6cb78..2c8512b 100644
> >>>> --- a/drivers/net/tap.c
> >>>> +++ b/drivers/net/tap.c
> >>>> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
> >>>>  		 *	  check, we either support them all or none.
> >>>>  		 */
> >>>>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
> >>>> -		    !(features & NETIF_F_CSUM_MASK) &&
> >>>> -		    skb_checksum_help(skb))
> >>>> +		    skb_csum_hwoffload_help(skb, features))
> >>>>  			goto drop;
> >>>>  		if (ptr_ring_produce(&q->ring, skb))
> >>>>  			goto drop;
> >>>> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
> >>>>  		}
> >>>>  	}
> >>>>  
> >>>> +	if (arg & TUN_F_SCTP_CSUM)
> >>>> +		feature_mask |= NETIF_F_SCTP_CRC;
> >>>> +
> >>>
> >>> so this still affects TX, shouldn't this affect RX instead?
> >>
> >> There is no bit to set on the RX path just like there is no bit to set on the RX patch
> >> for TUN_F_CSUM.
> >>
> >> We only invert TSO offloads, not checksum offloads as the comment below states.
> >> For checksum,  macvtap has to compute the checksum itself in tap_handle_frame() above.
> >> It uses tx feature bits to see if needs do to the checksum.
> >>
> >> If you think we need another flag to macvtap to control RXCSUM, that would need to be
> >> separate and cover standard TCP checksum as well.
> >>
> >> -vlad
> > 
> > Confused. What is the meaning of TUN_F_SCTP_CSUM? I assume this is
> > a way for userspace to tell tun device: "I can handle
> > packets without SCTP checksum, pls send them my way".
> 
> Yes,  just as TUN_F_CSUM means that tun device can handle packets with
> partial tcp/udp checksum.
> 
> > 
> > Now what is the implication for macvtap? 
> 
> The implication is exactly the same as for TUN_F_CSUM.  If the
> flag is set on the macvtap device, the TX checksum feature is
> turned on.

I guess I will have to go back and re-read that code - I do not remember
what does TUN_F_CSUM does by now.  Here is a quick question that might
help me:

Let's assume userspace does not set TUN_F_SCTP_CSUM and device
does not calculate the checksums either. I would expect that with
macvtap this then behaves exactly like now with no overhead.

> 
> > And why  are
> > you setting NETIF_F_SCTP_CRC which is a flag
> > that affects packets sent by guest to host?
> 
> Mainly its because we are using just 1 flag to control checksum
> offloading and we need to be able control both tx and rx paths.

Well that's not really the case I think. What we have is controls for tx
offloads for tun. That's TUN_F_CSUM.
there are no rx offloads - userspace can send what it wants.

These are supposed to translate to rx offloads for macvtap.
tx offloads shouldn't be affected at all.

Maybe that's not the case - as I said need to go back and check.
Will try to find the time in the next couple of days.

> What you are suggesting that we either invert what TUN_F_CSUM
> is doing in macvtap case, or have another flag that lets us control
> TX and RX paths separately.
> 
> Either case, that would be separate work.
> -vlad

So assuming TUN_F_CSUM affects tx for macvtap do you
agree it's a bug? And should we add to it with
TUN_F_SCTP_CSUM doing the same?

> > 
> > 
> >>>
> >>>
> >>>>  	/* tun/tap driver inverts the usage for TSO offloads, where
> >>>>  	 * setting the TSO bit means that the userspace wants to
> >>>>  	 * accept TSO frames and turning it off means that user space
> >>>> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
> >>>>  	case TUNSETOFFLOAD:
> >>>>  		/* let the user check for future flags */
> >>>>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> >>>> -			    TUN_F_TSO_ECN | TUN_F_UFO))
> >>>> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
> >>>>  			return -EINVAL;
> >>>>  
> >>>>  		rtnl_lock();
> >>>> -- 
> >>>> 2.9.5

Re: [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

[Vlad Yasevich]

On 05/02/2018 10:17 AM, Michael S. Tsirkin wrote:
> On Wed, May 02, 2018 at 10:00:14AM -0400, Vlad Yasevich wrote:
>> On 05/02/2018 09:46 AM, Michael S. Tsirkin wrote:
>>> On Wed, May 02, 2018 at 09:27:00AM -0400, Vlad Yasevich wrote:
>>>> On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
>>>>> On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
>>>>>> Since we now have support for software CRC32c offload, turn it on
>>>>>> for macvlan and macvtap devices so that guests can take advantage
>>>>>> of offload SCTP checksums to the host or host hardware.
>>>>>>
>>>>>> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
>>>>>> ---
>>>>>>  drivers/net/macvlan.c | 5 +++--
>>>>>>  drivers/net/tap.c     | 8 +++++---
>>>>>>  2 files changed, 8 insertions(+), 5 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
>>>>>> index 725f4b4..646b730 100644
>>>>>> --- a/drivers/net/macvlan.c
>>>>>> +++ b/drivers/net/macvlan.c
>>>>>> @@ -834,7 +834,7 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>>>>>>  
>>>>>>  #define ALWAYS_ON_OFFLOADS \
>>>>>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
>>>>>> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
>>>>>> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
>>>>>>  
>>>>>>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
>>>>>>  
>>>>>> @@ -842,7 +842,8 @@ static struct lock_class_key macvlan_netdev_addr_lock_key;
>>>>>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
>>>>>>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
>>>>>>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
>>>>>> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
>>>>>> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
>>>>>> +	 NETIF_F_SCTP_CRC)
>>>>>>  
>>>>>>  #define MACVLAN_STATE_MASK \
>>>>>>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
>>>>>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
>>>>>> index 9b6cb78..2c8512b 100644
>>>>>> --- a/drivers/net/tap.c
>>>>>> +++ b/drivers/net/tap.c
>>>>>> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
>>>>>>  		 *	  check, we either support them all or none.
>>>>>>  		 */
>>>>>>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
>>>>>> -		    !(features & NETIF_F_CSUM_MASK) &&
>>>>>> -		    skb_checksum_help(skb))
>>>>>> +		    skb_csum_hwoffload_help(skb, features))
>>>>>>  			goto drop;
>>>>>>  		if (ptr_ring_produce(&q->ring, skb))
>>>>>>  			goto drop;
>>>>>> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
>>>>>>  		}
>>>>>>  	}
>>>>>>  
>>>>>> +	if (arg & TUN_F_SCTP_CSUM)
>>>>>> +		feature_mask |= NETIF_F_SCTP_CRC;
>>>>>> +
>>>>>
>>>>> so this still affects TX, shouldn't this affect RX instead?
>>>>
>>>> There is no bit to set on the RX path just like there is no bit to set on the RX patch
>>>> for TUN_F_CSUM.
>>>>
>>>> We only invert TSO offloads, not checksum offloads as the comment below states.
>>>> For checksum,  macvtap has to compute the checksum itself in tap_handle_frame() above.
>>>> It uses tx feature bits to see if needs do to the checksum.
>>>>
>>>> If you think we need another flag to macvtap to control RXCSUM, that would need to be
>>>> separate and cover standard TCP checksum as well.
>>>>
>>>> -vlad
>>>
>>> Confused. What is the meaning of TUN_F_SCTP_CSUM? I assume this is
>>> a way for userspace to tell tun device: "I can handle
>>> packets without SCTP checksum, pls send them my way".
>>
>> Yes,  just as TUN_F_CSUM means that tun device can handle packets with
>> partial tcp/udp checksum.
>>
>>>
>>> Now what is the implication for macvtap? 
>>
>> The implication is exactly the same as for TUN_F_CSUM.  If the
>> flag is set on the macvtap device, the TX checksum feature is
>> turned on.
> 
> I guess I will have to go back and re-read that code - I do not remember
> what does TUN_F_CSUM does by now.  Here is a quick question that might
> help me:
> 
> Let's assume userspace does not set TUN_F_SCTP_CSUM and device
> does not calculate the checksums either. I would expect that with
> macvtap this then behaves exactly like now with no overhead.

correct.

> 
>>
>>> And why  are
>>> you setting NETIF_F_SCTP_CRC which is a flag
>>> that affects packets sent by guest to host?
>>
>> Mainly its because we are using just 1 flag to control checksum
>> offloading and we need to be able control both tx and rx paths.
> 
> Well that's not really the case I think. What we have is controls for tx
> offloads for tun. That's TUN_F_CSUM.
> there are no rx offloads - userspace can send what it wants.
> 
> These are supposed to translate to rx offloads for macvtap.
> tx offloads shouldn't be affected at all.

Ok.  This is how it works for TSO, but looks like there was a disconnect
on the checksum.   In both tun and macvtap case, TUN_F_CSUM controls
the tx checksum feature bit.

> 
> Maybe that's not the case - as I said need to go back and check.
> Will try to find the time in the next couple of days.
> 
>> What you are suggesting that we either invert what TUN_F_CSUM
>> is doing in macvtap case, or have another flag that lets us control
>> TX and RX paths separately.
>>
>> Either case, that would be separate work.
>> -vlad
> 
> So assuming TUN_F_CSUM affects tx for macvtap do you
> agree it's a bug? And should we add to it with
> TUN_F_SCTP_CSUM doing the same?

let me think about what it would look like if TUN_F_CSUM
controlled the rx bits...

-vlad

> 
>>>
>>>
>>>>>
>>>>>
>>>>>>  	/* tun/tap driver inverts the usage for TSO offloads, where
>>>>>>  	 * setting the TSO bit means that the userspace wants to
>>>>>>  	 * accept TSO frames and turning it off means that user space
>>>>>> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
>>>>>>  	case TUNSETOFFLOAD:
>>>>>>  		/* let the user check for future flags */
>>>>>>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
>>>>>> -			    TUN_F_TSO_ECN | TUN_F_UFO))
>>>>>> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
>>>>>>  			return -EINVAL;
>>>>>>  
>>>>>>  		rtnl_lock();
>>>>>> -- 
>>>>>> 2.9.5

Re: [PATCH V2 net-next 4/6] tun: Add support for SCTP checksum offload

[Vlad Yasevich]

On 05/02/2018 10:56 AM, Marcelo Ricardo Leitner wrote:
> On Wed, May 02, 2018 at 11:53:47AM -0300, Marcelo Ricardo Leitner wrote:
>> On Tue, May 01, 2018 at 10:07:37PM -0400, Vladislav Yasevich wrote:
>>> Adds a new tun offload flag to allow for SCTP checksum offload.
>>> The flag has to be set by the user and defaults to "no offload".
>>
>> I'm confused here:
>>
>>> +++ b/drivers/net/tun.c
>>> @@ -216,7 +216,7 @@ struct tun_struct {
>>>  	struct net_device	*dev;
>>>  	netdev_features_t	set_features;
>>>  #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
>>> -			  NETIF_F_TSO6)
>>> +			  NETIF_F_TSO6|NETIF_F_SCTP_CRC)
>>
>> Doesn't adding it here mean it defaults to "offload", instead?
>>
>> later on, it does:
>>                 dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
>>                                    TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
>>                                    NETIF_F_HW_VLAN_STAG_TX;
> 
> Missed to paste the next line too:
>                 dev->features = dev->hw_features | NETIF_F_LLTX;
> 

Yes, as a software device, we can default it to on.  However, qemu will 0-out
the features and then set them up based on the guest (just like regular checksum).

-vlad

RE: [PATCH V2 net-next 2/6] sctp: Handle sctp packets with CHECKSUM_PARTIAL

[David Laight]

From: Marcelo Ricardo Leitner
> Sent: 20 August 2018 15:54
> On Wed, May 02, 2018 at 11:38:24AM -0300, Marcelo Ricardo Leitner wrote:
> > On Tue, May 01, 2018 at 10:07:35PM -0400, Vladislav Yasevich wrote:
> > > With SCTP checksum offload available in virtio, it is now
> > > possible for virtio to receive a sctp packet with CHECKSUM_PARTIAL
> > > set (guest-to-guest traffic).  SCTP doesn't really have a
> > > partial checksum like TCP does, because CRC32c can't do partial
> > > additive checksumming.
...

Actually that isn't entirely true.
For all crc, crc(a) ^ crc(b) == crc(a^b).
Since crc(0) == 0 you can xor together two separately calculated crc
provided they both end at the same point.
The slight problem is that you are more likely to be appending
one buffer to another - which requires appending lots of zero
bytes to one of the crcs.
This could be speeded up by using lookup tables that add moderate
sized blocks of zero bytes to a crc instead of adding the zero
bytes one at a time.
Doing it without large const data and/or data cache trashing
is left as an exercise to the implementer.

	David

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