vxlan: Group Policy extension
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>
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 99df0d7..6dbf8e0 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -620,7 +620,8 @@
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;
}
@@ -1183,6 +1184,7 @@
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))
@@ -1216,6 +1218,24 @@
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
@@ -1229,7 +1249,8 @@
goto bad_flags;
}
- vs->rcv(vs, skb, vxh->vx_vni);
+ md.vni = vxh->vx_vni;
+ vs->rcv(vs, skb, &md);
return 0;
drop:
@@ -1246,8 +1267,8 @@
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;
@@ -1258,7 +1279,7 @@
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)
@@ -1292,6 +1313,7 @@
goto drop;
skb_reset_network_header(skb);
+ skb->mark = md->gbp;
if (oip6)
err = IP6_ECN_decapsulate(oip6, skb);
@@ -1641,13 +1663,30 @@
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;
@@ -1696,7 +1735,7 @@
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) >>
@@ -1714,6 +1753,9 @@
}
}
+ 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,
@@ -1728,7 +1770,8 @@
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;
@@ -1771,7 +1814,7 @@
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) >>
@@ -1789,6 +1832,9 @@
}
}
+ 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,
@@ -1849,6 +1895,7 @@
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;
@@ -1919,11 +1966,12 @@
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. */
@@ -1976,10 +2024,12 @@
}
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
}
@@ -2382,6 +2432,7 @@
[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[])
@@ -2706,6 +2757,9 @@
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);
@@ -2851,6 +2905,10 @@
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: