Commit 0c19f846 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

net: accept UFO datagrams from tuntap and packet 

Tuntap and similar devices can inject GSO packets. Accept type
VIRTIO_NET_HDR_GSO_UDP, even though not generating UFO natively.

Processes are expected to use feature negotiation such as TUNSETOFFLOAD
to detect supported offload types and refrain from injecting other
packets. This process breaks down with live migration: guest kernels
do not renegotiate flags, so destination hosts need to expose all
features that the source host does.

Partially revert the UFO removal from 182e0b6b~1..d9d30adf.
This patch introduces nearly(*) no new code to simplify verification.
It brings back verbatim tuntap UFO negotiation, VIRTIO_NET_HDR_GSO_UDP
insertion and software UFO segmentation.

It does not reinstate protocol stack support, hardware offload
(NETIF_F_UFO), SKB_GSO_UDP tunneling in SKB_GSO_SOFTWARE or reception
of VIRTIO_NET_HDR_GSO_UDP packets in tuntap.

To support SKB_GSO_UDP reappearing in the stack, also reinstate
logic in act_csum and openvswitch. Achieve equivalence with v4.13 HEAD
by squashing in commit 93991221 ("net: skb_needs_check() removes
CHECKSUM_UNNECESSARY check for tx.") and reverting commit 8d63bee6
("net: avoid skb_warn_bad_offload false positives on UFO").

(*) To avoid having to bring back skb_shinfo(skb)->ip6_frag_id,
ipv6_proxy_select_ident is changed to return a __be32 and this is
assigned directly to the frag_hdr. Also, SKB_GSO_UDP is inserted
at the end of the enum to minimize code churn.

Tested
  Booted a v4.13 guest kernel with QEMU. On a host kernel before this
  patch `ethtool -k eth0` shows UFO disabled. After the patch, it is
  enabled, same as on a v4.13 host kernel.

  A UFO packet sent from the guest appears on the tap device:
    host:
      nc -l -p -u 8000 &
      tcpdump -n -i tap0

    guest:
      dd if=/dev/zero of=payload.txt bs=1 count=2000
      nc -u 192.16.1.1 8000 < payload.txt

  Direct tap to tap transmission of VIRTIO_NET_HDR_GSO_UDP succeeds,
  packets arriving fragmented:

    ./with_tap_pair.sh ./tap_send_ufo tap0 tap1
    (from https://github.com/wdebruij/kerneltools/tree/master/tests)

Changes
  v1 -> v2
    - simplified set_offload change (review comment)
    - documented test procedure

Link: http://lkml.kernel.org/r/<CAF=yD-LuUeDuL9YWPJD9ykOZ0QCjNeznPDr6whqZ9NGMNF12Mw@mail.gmail.com

>
Fixes: fb652fdf ("macvlan/macvtap: Remove NETIF_F_UFO advertisement.")
Reported-by: default avatarMichal Kubecek <mkubecek@suse.cz>
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9e77d7a5

drivers/net/tap.c

+1 −1
Original line number Diff line number Diff line
@@ -1077,7 +1077,7 @@ 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_TSO_ECN | TUN_F_UFO))

			return -EINVAL;



		rtnl_lock();

drivers/net/tun.c

+2 −0
Original line number Diff line number Diff line
@@ -2370,6 +2370,8 @@ static int set_offload(struct tun_struct *tun, unsigned long arg) 
				features |= NETIF_F_TSO6;

			arg &= ~(TUN_F_TSO4|TUN_F_TSO6);

		}



		arg &= ~TUN_F_UFO;

	}



	/* This gives the user a way to test for new features in future by

include/linux/netdev_features.h

+3 −1
Original line number Diff line number Diff line
@@ -54,8 +54,9 @@ enum { 
	NETIF_F_GSO_TUNNEL_REMCSUM_BIT, /* ... TUNNEL with TSO & REMCSUM */

	NETIF_F_GSO_SCTP_BIT,		/* ... SCTP fragmentation */

	NETIF_F_GSO_ESP_BIT,		/* ... ESP with TSO */

	NETIF_F_GSO_UDP_BIT,		/* ... UFO, deprecated except tuntap */

	/**/NETIF_F_GSO_LAST =		/* last bit, see GSO_MASK */

		NETIF_F_GSO_ESP_BIT,

		NETIF_F_GSO_UDP_BIT,



	NETIF_F_FCOE_CRC_BIT,		/* FCoE CRC32 */

	NETIF_F_SCTP_CRC_BIT,		/* SCTP checksum offload */
@@ -132,6 +133,7 @@ enum { 
#define NETIF_F_GSO_TUNNEL_REMCSUM __NETIF_F(GSO_TUNNEL_REMCSUM)

#define NETIF_F_GSO_SCTP	__NETIF_F(GSO_SCTP)

#define NETIF_F_GSO_ESP		__NETIF_F(GSO_ESP)

#define NETIF_F_GSO_UDP		__NETIF_F(GSO_UDP)

#define NETIF_F_HW_VLAN_STAG_FILTER __NETIF_F(HW_VLAN_STAG_FILTER)

#define NETIF_F_HW_VLAN_STAG_RX	__NETIF_F(HW_VLAN_STAG_RX)

#define NETIF_F_HW_VLAN_STAG_TX	__NETIF_F(HW_VLAN_STAG_TX)

include/linux/netdevice.h

+1 −0
Original line number Diff line number Diff line
@@ -4140,6 +4140,7 @@ static inline bool net_gso_ok(netdev_features_t features, int gso_type) 
	BUILD_BUG_ON(SKB_GSO_TUNNEL_REMCSUM != (NETIF_F_GSO_TUNNEL_REMCSUM >> NETIF_F_GSO_SHIFT));

	BUILD_BUG_ON(SKB_GSO_SCTP    != (NETIF_F_GSO_SCTP >> NETIF_F_GSO_SHIFT));

	BUILD_BUG_ON(SKB_GSO_ESP != (NETIF_F_GSO_ESP >> NETIF_F_GSO_SHIFT));

	BUILD_BUG_ON(SKB_GSO_UDP != (NETIF_F_GSO_UDP >> NETIF_F_GSO_SHIFT));



	return (features & feature) == feature;

}

include/linux/skbuff.h

+2 −0
Original line number Diff line number Diff line
@@ -568,6 +568,8 @@ enum { 
	SKB_GSO_SCTP = 1 << 14,



	SKB_GSO_ESP = 1 << 15,



	SKB_GSO_UDP = 1 << 16,

};



#if BITS_PER_LONG > 32

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