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vxlan: Group Policy extension
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Implements supports for the Group Policy VXLAN extension [0] to provide
a lightweight and simple security label mechanism across network peers
based on VXLAN. The security context and associated metadata is mapped
to/from skb->mark. This allows further mapping to a SELinux context
using SECMARK, to implement ACLs directly with nftables, iptables, OVS,
tc, etc.

The group membership is defined by the lower 16 bits of skb->mark, the
upper 16 bits are used for flags.

SELinux allows to manage label to secure local resources. However,
distributed applications require ACLs to implemented across hosts. This
is typically achieved by matching on L2-L4 fields to identify the
original sending host and process on the receiver. On top of that,
netlabel and specifically CIPSO [1] allow to map security contexts to
universal labels.  However, netlabel and CIPSO are relatively complex.
This patch provides a lightweight alternative for overlay network
environments with a trusted underlay. No additional control protocol
is required.

           Host 1:                       Host 2:

      Group A        Group B        Group B     Group A
      +-----+   +-------------+    +-------+   +-----+
      | lxc |   | SELinux CTX |    | httpd |   | VM  |
      +--+--+   +--+----------+    +---+---+   +--+--+
	  \---+---/                     \----+---/
	      |                              |
	  +---+---+                      +---+---+
	  | vxlan |                      | vxlan |
	  +---+---+                      +---+---+
	      +------------------------------+

Backwards compatibility:
A VXLAN-GBP socket can receive standard VXLAN frames and will assign
the default group 0x0000 to such frames. A Linux VXLAN socket will
drop VXLAN-GBP  frames. The extension is therefore disabled by default
and needs to be specifically enabled:

   ip link add [...] type vxlan [...] gbp

In a mixed environment with VXLAN and VXLAN-GBP sockets, the GBP socket
must run on a separate port number.

Examples:
 iptables:
  host1# iptables -I OUTPUT -m owner --uid-owner 101 -j MARK --set-mark 0x200
  host2# iptables -I INPUT -m mark --mark 0x200 -j DROP

 OVS:
  # ovs-ofctl add-flow br0 'in_port=1,actions=load:0x200->NXM_NX_TUN_GBP_ID[],NORMAL'
  # ovs-ofctl add-flow br0 'in_port=2,tun_gbp_id=0x200,actions=drop'

[0] https://tools.ietf.org/html/draft-smith-vxlan-group-policy
[1] http://lwn.net/Articles/204905/

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@tgraf @davem330
tgraf authored and davem330 committed Jan 15, 2015
1 parent 3f3558b commit 3511494
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Showing 4 changed files with 152 additions and 21 deletions.
84 changes: 71 additions & 13 deletions drivers/net/vxlan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -620,7 +620,8 @@ static struct sk_buff **vxlan_gro_receive(struct sk_buff **head,
continue;

vh2 = (struct vxlanhdr *)(p->data + off_vx);
if (vh->vx_vni != vh2->vx_vni) {
if (vh->vx_flags != vh2->vx_flags ||
vh->vx_vni != vh2->vx_vni) {
NAPI_GRO_CB(p)->same_flow = 0;
continue;
}
Expand Down Expand Up @@ -1183,6 +1184,7 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
struct vxlan_sock *vs;
struct vxlanhdr *vxh;
u32 flags, vni;
struct vxlan_metadata md = {0};

/* Need Vxlan and inner Ethernet header to be present */
if (!pskb_may_pull(skb, VXLAN_HLEN))
Expand Down Expand Up @@ -1216,6 +1218,24 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
vni &= VXLAN_VID_MASK;
}

/* For backwards compatibility, only allow reserved fields to be
* used by VXLAN extensions if explicitly requested.
*/
if ((flags & VXLAN_HF_GBP) && (vs->flags & VXLAN_F_GBP)) {
struct vxlanhdr_gbp *gbp;

gbp = (struct vxlanhdr_gbp *)vxh;
md.gbp = ntohs(gbp->policy_id);

if (gbp->dont_learn)
md.gbp |= VXLAN_GBP_DONT_LEARN;

if (gbp->policy_applied)
md.gbp |= VXLAN_GBP_POLICY_APPLIED;

flags &= ~VXLAN_GBP_USED_BITS;
}

if (flags || (vni & ~VXLAN_VID_MASK)) {
/* If there are any unprocessed flags remaining treat
* this as a malformed packet. This behavior diverges from
Expand All @@ -1229,7 +1249,8 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
goto bad_flags;
}

vs->rcv(vs, skb, vxh->vx_vni);
md.vni = vxh->vx_vni;
vs->rcv(vs, skb, &md);
return 0;

drop:
Expand All @@ -1246,8 +1267,8 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
return 1;
}

static void vxlan_rcv(struct vxlan_sock *vs,
struct sk_buff *skb, __be32 vx_vni)
static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb,
struct vxlan_metadata *md)
{
struct iphdr *oip = NULL;
struct ipv6hdr *oip6 = NULL;
Expand All @@ -1258,7 +1279,7 @@ static void vxlan_rcv(struct vxlan_sock *vs,
int err = 0;
union vxlan_addr *remote_ip;

vni = ntohl(vx_vni) >> 8;
vni = ntohl(md->vni) >> 8;
/* Is this VNI defined? */
vxlan = vxlan_vs_find_vni(vs, vni);
if (!vxlan)
Expand Down Expand Up @@ -1292,6 +1313,7 @@ static void vxlan_rcv(struct vxlan_sock *vs,
goto drop;

skb_reset_network_header(skb);
skb->mark = md->gbp;

if (oip6)
err = IP6_ECN_decapsulate(oip6, skb);
Expand Down Expand Up @@ -1641,13 +1663,30 @@ static bool route_shortcircuit(struct net_device *dev, struct sk_buff *skb)
return false;
}

static void vxlan_build_gbp_hdr(struct vxlanhdr *vxh, struct vxlan_sock *vs,
struct vxlan_metadata *md)
{
struct vxlanhdr_gbp *gbp;

gbp = (struct vxlanhdr_gbp *)vxh;
vxh->vx_flags |= htonl(VXLAN_HF_GBP);

if (md->gbp & VXLAN_GBP_DONT_LEARN)
gbp->dont_learn = 1;

if (md->gbp & VXLAN_GBP_POLICY_APPLIED)
gbp->policy_applied = 1;

gbp->policy_id = htons(md->gbp & VXLAN_GBP_ID_MASK);
}

#if IS_ENABLED(CONFIG_IPV6)
static int vxlan6_xmit_skb(struct vxlan_sock *vs,
struct dst_entry *dst, struct sk_buff *skb,
struct net_device *dev, struct in6_addr *saddr,
struct in6_addr *daddr, __u8 prio, __u8 ttl,
__be16 src_port, __be16 dst_port, __be32 vni,
bool xnet)
__be16 src_port, __be16 dst_port,
struct vxlan_metadata *md, bool xnet)
{
struct vxlanhdr *vxh;
int min_headroom;
Expand Down Expand Up @@ -1696,7 +1735,7 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,

vxh = (struct vxlanhdr *) __skb_push(skb, sizeof(*vxh));
vxh->vx_flags = htonl(VXLAN_HF_VNI);
vxh->vx_vni = vni;
vxh->vx_vni = md->vni;

if (type & SKB_GSO_TUNNEL_REMCSUM) {
u32 data = (skb_checksum_start_offset(skb) - hdrlen) >>
Expand All @@ -1714,6 +1753,9 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
}
}

if (vs->flags & VXLAN_F_GBP)
vxlan_build_gbp_hdr(vxh, vs, md);

skb_set_inner_protocol(skb, htons(ETH_P_TEB));

udp_tunnel6_xmit_skb(vs->sock, dst, skb, dev, saddr, daddr, prio,
Expand All @@ -1728,7 +1770,8 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
int vxlan_xmit_skb(struct vxlan_sock *vs,
struct rtable *rt, struct sk_buff *skb,
__be32 src, __be32 dst, __u8 tos, __u8 ttl, __be16 df,
__be16 src_port, __be16 dst_port, __be32 vni, bool xnet)
__be16 src_port, __be16 dst_port,
struct vxlan_metadata *md, bool xnet)
{
struct vxlanhdr *vxh;
int min_headroom;
Expand Down Expand Up @@ -1771,7 +1814,7 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,

vxh = (struct vxlanhdr *) __skb_push(skb, sizeof(*vxh));
vxh->vx_flags = htonl(VXLAN_HF_VNI);
vxh->vx_vni = vni;
vxh->vx_vni = md->vni;

if (type & SKB_GSO_TUNNEL_REMCSUM) {
u32 data = (skb_checksum_start_offset(skb) - hdrlen) >>
Expand All @@ -1789,6 +1832,9 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
}
}

if (vs->flags & VXLAN_F_GBP)
vxlan_build_gbp_hdr(vxh, vs, md);

skb_set_inner_protocol(skb, htons(ETH_P_TEB));

return udp_tunnel_xmit_skb(vs->sock, rt, skb, src, dst, tos,
Expand Down Expand Up @@ -1849,6 +1895,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
const struct iphdr *old_iph;
struct flowi4 fl4;
union vxlan_addr *dst;
struct vxlan_metadata md;
__be16 src_port = 0, dst_port;
u32 vni;
__be16 df = 0;
Expand Down Expand Up @@ -1919,11 +1966,12 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,

tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
md.vni = htonl(vni << 8);
md.gbp = skb->mark;

err = vxlan_xmit_skb(vxlan->vn_sock, rt, skb,
fl4.saddr, dst->sin.sin_addr.s_addr,
tos, ttl, df, src_port, dst_port,
htonl(vni << 8),
tos, ttl, df, src_port, dst_port, &md,
!net_eq(vxlan->net, dev_net(vxlan->dev)));
if (err < 0) {
/* skb is already freed. */
Expand Down Expand Up @@ -1976,10 +2024,12 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
}

ttl = ttl ? : ip6_dst_hoplimit(ndst);
md.vni = htonl(vni << 8);
md.gbp = skb->mark;

err = vxlan6_xmit_skb(vxlan->vn_sock, ndst, skb,
dev, &fl6.saddr, &fl6.daddr, 0, ttl,
src_port, dst_port, htonl(vni << 8),
src_port, dst_port, &md,
!net_eq(vxlan->net, dev_net(vxlan->dev)));
#endif
}
Expand Down Expand Up @@ -2382,6 +2432,7 @@ static const struct nla_policy vxlan_policy[IFLA_VXLAN_MAX + 1] = {
[IFLA_VXLAN_UDP_ZERO_CSUM6_RX] = { .type = NLA_U8 },
[IFLA_VXLAN_REMCSUM_TX] = { .type = NLA_U8 },
[IFLA_VXLAN_REMCSUM_RX] = { .type = NLA_U8 },
[IFLA_VXLAN_GBP] = { .type = NLA_FLAG, },
};

static int vxlan_validate(struct nlattr *tb[], struct nlattr *data[])
Expand Down Expand Up @@ -2706,6 +2757,9 @@ static int vxlan_newlink(struct net *net, struct net_device *dev,
nla_get_u8(data[IFLA_VXLAN_REMCSUM_RX]))
vxlan->flags |= VXLAN_F_REMCSUM_RX;

if (data[IFLA_VXLAN_GBP])
vxlan->flags |= VXLAN_F_GBP;

if (vxlan_find_vni(net, vni, use_ipv6 ? AF_INET6 : AF_INET,
vxlan->dst_port)) {
pr_info("duplicate VNI %u\n", vni);
Expand Down Expand Up @@ -2851,6 +2905,10 @@ static int vxlan_fill_info(struct sk_buff *skb, const struct net_device *dev)
if (nla_put(skb, IFLA_VXLAN_PORT_RANGE, sizeof(ports), &ports))
goto nla_put_failure;

if (vxlan->flags & VXLAN_F_GBP &&
nla_put_flag(skb, IFLA_VXLAN_GBP))
goto nla_put_failure;

return 0;

nla_put_failure:
Expand Down
79 changes: 74 additions & 5 deletions include/net/vxlan.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,15 +11,76 @@
#define VNI_HASH_BITS 10
#define VNI_HASH_SIZE (1<<VNI_HASH_BITS)

/* VXLAN protocol header */
/*
* VXLAN Group Based Policy Extension:
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |1|-|-|-|1|-|-|-|R|D|R|R|A|R|R|R| Group Policy ID |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | VXLAN Network Identifier (VNI) | Reserved |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* D = Don't Learn bit. When set, this bit indicates that the egress
* VTEP MUST NOT learn the source address of the encapsulated frame.
*
* A = Indicates that the group policy has already been applied to
* this packet. Policies MUST NOT be applied by devices when the
* A bit is set.
*
* [0] https://tools.ietf.org/html/draft-smith-vxlan-group-policy
*/
struct vxlanhdr_gbp {
__u8 vx_flags;
#ifdef __LITTLE_ENDIAN_BITFIELD
__u8 reserved_flags1:3,
policy_applied:1,
reserved_flags2:2,
dont_learn:1,
reserved_flags3:1;
#elif defined(__BIG_ENDIAN_BITFIELD)
__u8 reserved_flags1:1,
dont_learn:1,
reserved_flags2:2,
policy_applied:1,
reserved_flags3:3;
#else
#error "Please fix <asm/byteorder.h>"
#endif
__be16 policy_id;
__be32 vx_vni;
};

#define VXLAN_GBP_USED_BITS (VXLAN_HF_GBP | 0xFFFFFF)

/* skb->mark mapping
*
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |R|R|R|R|R|R|R|R|R|D|R|R|A|R|R|R| Group Policy ID |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
#define VXLAN_GBP_DONT_LEARN (BIT(6) << 16)
#define VXLAN_GBP_POLICY_APPLIED (BIT(3) << 16)
#define VXLAN_GBP_ID_MASK (0xFFFF)

/* VXLAN protocol header:
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |G|R|R|R|I|R|R|C| Reserved |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | VXLAN Network Identifier (VNI) | Reserved |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* G = 1 Group Policy (VXLAN-GBP)
* I = 1 VXLAN Network Identifier (VNI) present
* C = 1 Remote checksum offload (RCO)
*/
struct vxlanhdr {
__be32 vx_flags;
__be32 vx_vni;
};

/* VXLAN header flags. */
#define VXLAN_HF_VNI 0x08000000
#define VXLAN_HF_RCO 0x00200000
#define VXLAN_HF_RCO BIT(24)
#define VXLAN_HF_VNI BIT(27)
#define VXLAN_HF_GBP BIT(31)

/* Remote checksum offload header option */
#define VXLAN_RCO_MASK 0x7f /* Last byte of vni field */
Expand All @@ -32,8 +93,14 @@ struct vxlanhdr {
#define VXLAN_VID_MASK (VXLAN_N_VID - 1)
#define VXLAN_HLEN (sizeof(struct udphdr) + sizeof(struct vxlanhdr))

struct vxlan_metadata {
__be32 vni;
u32 gbp;
};

struct vxlan_sock;
typedef void (vxlan_rcv_t)(struct vxlan_sock *vh, struct sk_buff *skb, __be32 key);
typedef void (vxlan_rcv_t)(struct vxlan_sock *vh, struct sk_buff *skb,
struct vxlan_metadata *md);

/* per UDP socket information */
struct vxlan_sock {
Expand All @@ -60,6 +127,7 @@ struct vxlan_sock {
#define VXLAN_F_UDP_ZERO_CSUM6_RX 0x100
#define VXLAN_F_REMCSUM_TX 0x200
#define VXLAN_F_REMCSUM_RX 0x400
#define VXLAN_F_GBP 0x800

struct vxlan_sock *vxlan_sock_add(struct net *net, __be16 port,
vxlan_rcv_t *rcv, void *data,
Expand All @@ -70,7 +138,8 @@ void vxlan_sock_release(struct vxlan_sock *vs);
int vxlan_xmit_skb(struct vxlan_sock *vs,
struct rtable *rt, struct sk_buff *skb,
__be32 src, __be32 dst, __u8 tos, __u8 ttl, __be16 df,
__be16 src_port, __be16 dst_port, __be32 vni, bool xnet);
__be16 src_port, __be16 dst_port, struct vxlan_metadata *md,
bool xnet);

static inline netdev_features_t vxlan_features_check(struct sk_buff *skb,
netdev_features_t features)
Expand Down
1 change: 1 addition & 0 deletions include/uapi/linux/if_link.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,7 @@ enum {
IFLA_VXLAN_UDP_ZERO_CSUM6_RX,
IFLA_VXLAN_REMCSUM_TX,
IFLA_VXLAN_REMCSUM_RX,
IFLA_VXLAN_GBP,
__IFLA_VXLAN_MAX
};
#define IFLA_VXLAN_MAX (__IFLA_VXLAN_MAX - 1)
Expand Down
9 changes: 6 additions & 3 deletions net/openvswitch/vport-vxlan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,8 @@ static inline struct vxlan_port *vxlan_vport(const struct vport *vport)
}

/* Called with rcu_read_lock and BH disabled. */
static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb, __be32 vx_vni)
static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb,
struct vxlan_metadata *md)
{
struct ovs_tunnel_info tun_info;
struct vport *vport = vs->data;
Expand All @@ -68,7 +69,7 @@ static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb, __be32 vx_vni)

/* Save outer tunnel values */
iph = ip_hdr(skb);
key = cpu_to_be64(ntohl(vx_vni) >> 8);
key = cpu_to_be64(ntohl(md->vni) >> 8);
ovs_flow_tun_info_init(&tun_info, iph,
udp_hdr(skb)->source, udp_hdr(skb)->dest,
key, TUNNEL_KEY, NULL, 0);
Expand Down Expand Up @@ -146,6 +147,7 @@ static int vxlan_tnl_send(struct vport *vport, struct sk_buff *skb)
struct vxlan_port *vxlan_port = vxlan_vport(vport);
__be16 dst_port = inet_sk(vxlan_port->vs->sock->sk)->inet_sport;
const struct ovs_key_ipv4_tunnel *tun_key;
struct vxlan_metadata md = {0};
struct rtable *rt;
struct flowi4 fl;
__be16 src_port;
Expand All @@ -170,12 +172,13 @@ static int vxlan_tnl_send(struct vport *vport, struct sk_buff *skb)
skb->ignore_df = 1;

src_port = udp_flow_src_port(net, skb, 0, 0, true);
md.vni = htonl(be64_to_cpu(tun_key->tun_id) << 8);

err = vxlan_xmit_skb(vxlan_port->vs, rt, skb,
fl.saddr, tun_key->ipv4_dst,
tun_key->ipv4_tos, tun_key->ipv4_ttl, df,
src_port, dst_port,
htonl(be64_to_cpu(tun_key->tun_id) << 8),
&md,
false);
if (err < 0)
ip_rt_put(rt);
Expand Down

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