On Tue, Jan 6, 2015 at 6:05 PM, Thomas Graf <tg...@suug.ch> wrote:
> The VXLAN receive code is currently conservative in what it accepts and
> will reject any frame that uses any of the reserved VXLAN protocol fields.
> The VXLAN draft specifies that "reserved fields MUST be set to zero on
> transmit and ignored on receive.".
>
IMO it is an unfortunate decision in VXLAN to ignore set reserved
fields on receive. Had they not done this, then adding a protocol
field to the header would have been feasible and we wouldn't need yet
another encapsulation protocol (i.e. VXLAN-GPE). Rejecting frames with
reserved bits set is the better behavior, but I think the comment
about this needs to be clear about why this diverges from RFC7348.
> Retain the current conservative parsing behaviour by default but allows
> these fields to be used by VXLAN extensions which are explicitly enabled
> on the VXLAN socket respectively VXLAN net_device.
>
Conceptually, VXLAN has both mandatory flags and optional flags for
extensions. You may want to look at the VXLAN RCO patches that added
an extension and infrastructure for them.
Tom
> Signed-off-by: Thomas Graf <tg...@suug.ch>
> ---
> drivers/net/vxlan.c | 29 +++++++++++++++++++----------
> include/net/vxlan.h | 32 +++++++++++++++++++++++++++++---
> 2 files changed, 48 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> index 2ab0922..4d52aa9 100644
> --- a/drivers/net/vxlan.c
> +++ b/drivers/net/vxlan.c
> @@ -65,7 +65,7 @@
> #define VXLAN_VID_MASK (VXLAN_N_VID - 1)
> #define VXLAN_HLEN (sizeof(struct udphdr) + sizeof(struct vxlanhdr))
>
> -#define VXLAN_FLAGS 0x08000000 /* struct vxlanhdr.vx_flags required value. */
> +#define VXLAN_FLAGS 0x08000000 /* struct vxlanhdr.vx_flags default value. */
>
> /* UDP port for VXLAN traffic.
> * The IANA assigned port is 4789, but the Linux default is 8472
> @@ -1100,22 +1100,28 @@ static int vxlan_udp_encap_recv(struct sock *sk,
> struct sk_buff *skb)
> if (!pskb_may_pull(skb, VXLAN_HLEN))
> goto error;
>
> + vs = rcu_dereference_sk_user_data(sk);
> + if (!vs)
> + goto drop;
> +
> /* Return packets with reserved bits set */
> vxh = (struct vxlanhdr *)(udp_hdr(skb) + 1);
> - if (vxh->vx_flags != htonl(VXLAN_FLAGS) ||
> - (vxh->vx_vni & htonl(0xff))) {
> - netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
> - ntohl(vxh->vx_flags), ntohl(vxh->vx_vni));
> - goto error;
> +
> + /* For backwards compatibility, only allow reserved fields to be
> + * used by VXLAN extensions if explicitly requested.
> + */
> + if (vs->exts) {
> + if (!vxh->vni_present)
> + goto error_invalid_header;
> + } else {
> + if (vxh->vx_flags != htonl(VXLAN_FLAGS) ||
> + (vxh->vx_vni & htonl(0xff)))
> + goto error_invalid_header;
> }
>
> if (iptunnel_pull_header(skb, VXLAN_HLEN, htons(ETH_P_TEB)))
> goto drop;
>
> - vs = rcu_dereference_sk_user_data(sk);
> - if (!vs)
> - goto drop;
> -
> vs->rcv(vs, skb, vxh->vx_vni);
> return 0;
>
> @@ -1124,6 +1130,9 @@ drop:
> kfree_skb(skb);
> return 0;
>
> +error_invalid_header:
> + netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
> + ntohl(vxh->vx_flags), ntohl(vxh->vx_vni));
> error:
> /* Return non vxlan pkt */
> return 1;
> diff --git a/include/net/vxlan.h b/include/net/vxlan.h
> index 903461a..3e98d31 100644
> --- a/include/net/vxlan.h
> +++ b/include/net/vxlan.h
> @@ -11,10 +11,35 @@
> #define VNI_HASH_BITS 10
> #define VNI_HASH_SIZE (1<<VNI_HASH_BITS)
>
> -/* VXLAN protocol header */
> +/* VXLAN protocol header:
> + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> + * |R|R|R|R|I|R|R|R| Reserved |
> + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> + * | VXLAN Network Identifier (VNI) | Reserved |
> + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> + *
> + * I = 1 VXLAN Network Identifier (VNI) present
> + */
> struct vxlanhdr {
> - __be32 vx_flags;
> - __be32 vx_vni;
> + union {
> + struct {
> +#ifdef __LITTLE_ENDIAN_BITFIELD
> + __u8 reserved_flags1:3,
> + vni_present:1,
> + reserved_flags2:4;
> +#elif defined(__BIG_ENDIAN_BITFIELD)
> + __u8 reserved_flags2:4,
> + vni_present:1,
> + reserved_flags1:3;
> +#else
> +#error "Please fix <asm/byteorder.h>"
> +#endif
> + __u8 vx_reserved1;
> + __be16 vx_reserved2;
> + };
> + __be32 vx_flags;
> + };
> + __be32 vx_vni;
> };
>
> struct vxlan_sock;
> @@ -25,6 +50,7 @@ struct vxlan_sock {
> struct hlist_node hlist;
> vxlan_rcv_t *rcv;
> void *data;
> + u32 exts;
> struct work_struct del_work;
> struct socket *sock;
> struct rcu_head rcu;
> --
> 1.9.3
>
> --
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