[PATCH/v4] bpf: add bpf_skb_adjust_room flag BPF_F_ADJ_ROOM_ENCAP_L2_ETH

From: Xuesen Huang
Date: Wed Mar 03 2021 - 12:11:22 EST

From: Xuesen Huang <huangxuesen@xxxxxxxxxxxx>

bpf_skb_adjust_room sets the inner_protocol as skb->protocol for packets
encapsulation. But that is not appropriate when pushing Ethernet header.

Add an option to further specify encap L2 type and set the inner_protocol
as ETH_P_TEB.

Update test_tc_tunnel to verify adding vxlan encapsulation works with
this flag.

Suggested-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: Xuesen Huang <huangxuesen@xxxxxxxxxxxx>
Signed-off-by: Zhiyong Cheng <chengzhiyong@xxxxxxxxxxxx>
Signed-off-by: Li Wang <wangli09@xxxxxxxxxxxx>
---
include/uapi/linux/bpf.h | 5 +
net/core/filter.c | 11 ++-
tools/include/uapi/linux/bpf.h | 5 +
tools/testing/selftests/bpf/progs/test_tc_tunnel.c | 107 ++++++++++++++++++---
tools/testing/selftests/bpf/test_tc_tunnel.sh | 15 ++-
5 files changed, 124 insertions(+), 19 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 77d7c1b..d791596 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1751,6 +1751,10 @@ struct bpf_stack_build_id {
* Use with ENCAP_L3/L4 flags to further specify the tunnel
* type; *len* is the length of the inner MAC header.
*
+ * * **BPF_F_ADJ_ROOM_ENCAP_L2_ETH**:
+ * Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
+ * L2 type as Ethernet.
+ *
* A call to this helper is susceptible to change the underlying
* packet buffer. Therefore, at load time, all checks on pointers
* previously done by the verifier are invalidated and must be
@@ -4088,6 +4092,7 @@ enum {
BPF_F_ADJ_ROOM_ENCAP_L4_GRE = (1ULL << 3),
BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4),
BPF_F_ADJ_ROOM_NO_CSUM_RESET = (1ULL << 5),
+ BPF_F_ADJ_ROOM_ENCAP_L2_ETH = (1ULL << 6),
};

enum {
diff --git a/net/core/filter.c b/net/core/filter.c
index 255aeee..8d1fb61 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3412,6 +3412,7 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \
BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \
BPF_F_ADJ_ROOM_ENCAP_L4_UDP | \
+ BPF_F_ADJ_ROOM_ENCAP_L2_ETH | \
BPF_F_ADJ_ROOM_ENCAP_L2( \
BPF_ADJ_ROOM_ENCAP_L2_MASK))

@@ -3448,6 +3449,10 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
flags & BPF_F_ADJ_ROOM_ENCAP_L4_UDP)
return -EINVAL;

+ if (flags & BPF_F_ADJ_ROOM_ENCAP_L2_ETH &&
+ inner_mac_len < ETH_HLEN)
+ return -EINVAL;
+
if (skb->encapsulation)
return -EALREADY;

@@ -3466,7 +3471,11 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
skb->inner_mac_header = inner_net - inner_mac_len;
skb->inner_network_header = inner_net;
skb->inner_transport_header = inner_trans;
- skb_set_inner_protocol(skb, skb->protocol);
+
+ if (flags & BPF_F_ADJ_ROOM_ENCAP_L2_ETH)
+ skb_set_inner_protocol(skb, htons(ETH_P_TEB));
+ else
+ skb_set_inner_protocol(skb, skb->protocol);

skb->encapsulation = 1;
skb_set_network_header(skb, mac_len);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 77d7c1b..d791596 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1751,6 +1751,10 @@ struct bpf_stack_build_id {
* Use with ENCAP_L3/L4 flags to further specify the tunnel
* type; *len* is the length of the inner MAC header.
*
+ * * **BPF_F_ADJ_ROOM_ENCAP_L2_ETH**:
+ * Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
+ * L2 type as Ethernet.
+ *
* A call to this helper is susceptible to change the underlying
* packet buffer. Therefore, at load time, all checks on pointers
* previously done by the verifier are invalidated and must be
@@ -4088,6 +4092,7 @@ enum {
BPF_F_ADJ_ROOM_ENCAP_L4_GRE = (1ULL << 3),
BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4),
BPF_F_ADJ_ROOM_NO_CSUM_RESET = (1ULL << 5),
+ BPF_F_ADJ_ROOM_ENCAP_L2_ETH = (1ULL << 6),
};

enum {
diff --git a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
index 37bce7a..6e144db 100644
--- a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
+++ b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
@@ -20,6 +20,14 @@
#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>

+#define encap_ipv4(...) __encap_ipv4(__VA_ARGS__, 0)
+
+#define encap_ipv4_with_ext_proto(...) __encap_ipv4(__VA_ARGS__)
+
+#define encap_ipv6(...) __encap_ipv6(__VA_ARGS__, 0)
+
+#define encap_ipv6_with_ext_proto(...) __encap_ipv6(__VA_ARGS__)
+
static const int cfg_port = 8000;

static const int cfg_udp_src = 20000;
@@ -27,11 +35,24 @@
#define UDP_PORT 5555
#define MPLS_OVER_UDP_PORT 6635
#define ETH_OVER_UDP_PORT 7777
+#define VXLAN_UDP_PORT 8472
+
+#define EXTPROTO_VXLAN 0x1
+
+#define VXLAN_N_VID (1u << 24)
+#define VXLAN_VNI_MASK bpf_htonl((VXLAN_N_VID - 1) << 8)
+#define VXLAN_FLAGS 0x8
+#define VXLAN_VNI 1

/* MPLS label 1000 with S bit (last label) set and ttl of 255. */
static const __u32 mpls_label = __bpf_constant_htonl(1000 << 12 |
MPLS_LS_S_MASK | 0xff);

+struct vxlanhdr {
+ __be32 vx_flags;
+ __be32 vx_vni;
+} __attribute__((packed));
+
struct gre_hdr {
__be16 flags;
__be16 protocol;
@@ -45,13 +66,13 @@ struct gre_hdr {
struct v4hdr {
struct iphdr ip;
union l4hdr l4hdr;
- __u8 pad[16]; /* enough space for L2 header */
+ __u8 pad[24]; /* space for L2 header / vxlan header ... */
} __attribute__((packed));

struct v6hdr {
struct ipv6hdr ip;
union l4hdr l4hdr;
- __u8 pad[16]; /* enough space for L2 header */
+ __u8 pad[24]; /* space for L2 header / vxlan header ... */
} __attribute__((packed));

static __always_inline void set_ipv4_csum(struct iphdr *iph)
@@ -69,14 +90,15 @@ static __always_inline void set_ipv4_csum(struct iphdr *iph)
iph->check = ~((csum & 0xffff) + (csum >> 16));
}

-static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
- __u16 l2_proto)
+static __always_inline int __encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
+ __u16 l2_proto, __u16 ext_proto)
{
__u16 udp_dst = UDP_PORT;
struct iphdr iph_inner;
struct v4hdr h_outer;
struct tcphdr tcph;
int olen, l2_len;
+ __u8 *l2_hdr = NULL;
int tcp_off;
__u64 flags;

@@ -141,7 +163,11 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
break;
case ETH_P_TEB:
l2_len = ETH_HLEN;
- udp_dst = ETH_OVER_UDP_PORT;
+ if (ext_proto & EXTPROTO_VXLAN) {
+ udp_dst = VXLAN_UDP_PORT;
+ l2_len += sizeof(struct vxlanhdr);
+ } else
+ udp_dst = ETH_OVER_UDP_PORT;
break;
}
flags |= BPF_F_ADJ_ROOM_ENCAP_L2(l2_len);
@@ -171,14 +197,26 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
}

/* add L2 encap (if specified) */
+ l2_hdr = (__u8 *)&h_outer + olen;
switch (l2_proto) {
case ETH_P_MPLS_UC:
- *((__u32 *)((__u8 *)&h_outer + olen)) = mpls_label;
+ *(__u32 *)l2_hdr = mpls_label;
break;
case ETH_P_TEB:
- if (bpf_skb_load_bytes(skb, 0, (__u8 *)&h_outer + olen,
- ETH_HLEN))
+ flags |= BPF_F_ADJ_ROOM_ENCAP_L2_ETH;
+
+ if (ext_proto & EXTPROTO_VXLAN) {
+ struct vxlanhdr *vxlan_hdr = (struct vxlanhdr *)l2_hdr;
+
+ vxlan_hdr->vx_flags = VXLAN_FLAGS;
+ vxlan_hdr->vx_vni = bpf_htonl((VXLAN_VNI & VXLAN_VNI_MASK) << 8);
+
+ l2_hdr += sizeof(struct vxlanhdr);
+ }
+
+ if (bpf_skb_load_bytes(skb, 0, l2_hdr, ETH_HLEN))
return TC_ACT_SHOT;
+
break;
}
olen += l2_len;
@@ -214,14 +252,15 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
return TC_ACT_OK;
}

-static __always_inline int encap_ipv6(struct __sk_buff *skb, __u8 encap_proto,
- __u16 l2_proto)
+static __always_inline int __encap_ipv6(struct __sk_buff *skb, __u8 encap_proto,
+ __u16 l2_proto, __u16 ext_proto)
{
__u16 udp_dst = UDP_PORT;
struct ipv6hdr iph_inner;
struct v6hdr h_outer;
struct tcphdr tcph;
int olen, l2_len;
+ __u8 *l2_hdr = NULL;
__u16 tot_len;
__u64 flags;

@@ -249,7 +288,11 @@ static __always_inline int encap_ipv6(struct __sk_buff *skb, __u8 encap_proto,
break;
case ETH_P_TEB:
l2_len = ETH_HLEN;
- udp_dst = ETH_OVER_UDP_PORT;
+ if (ext_proto & EXTPROTO_VXLAN) {
+ udp_dst = VXLAN_UDP_PORT;
+ l2_len += sizeof(struct vxlanhdr);
+ } else
+ udp_dst = ETH_OVER_UDP_PORT;
break;
}
flags |= BPF_F_ADJ_ROOM_ENCAP_L2(l2_len);
@@ -267,7 +310,7 @@ static __always_inline int encap_ipv6(struct __sk_buff *skb, __u8 encap_proto,
h_outer.l4hdr.udp.source = __bpf_constant_htons(cfg_udp_src);
h_outer.l4hdr.udp.dest = bpf_htons(udp_dst);
tot_len = bpf_ntohs(iph_inner.payload_len) + sizeof(iph_inner) +
- sizeof(h_outer.l4hdr.udp);
+ sizeof(h_outer.l4hdr.udp) + l2_len;
h_outer.l4hdr.udp.check = 0;
h_outer.l4hdr.udp.len = bpf_htons(tot_len);
break;
@@ -278,13 +321,24 @@ static __always_inline int encap_ipv6(struct __sk_buff *skb, __u8 encap_proto,
}

/* add L2 encap (if specified) */
+ l2_hdr = (__u8 *)&h_outer + olen;
switch (l2_proto) {
case ETH_P_MPLS_UC:
- *((__u32 *)((__u8 *)&h_outer + olen)) = mpls_label;
+ *(__u32 *)l2_hdr = mpls_label;
break;
case ETH_P_TEB:
- if (bpf_skb_load_bytes(skb, 0, (__u8 *)&h_outer + olen,
- ETH_HLEN))
+ flags |= BPF_F_ADJ_ROOM_ENCAP_L2_ETH;
+
+ if (ext_proto & EXTPROTO_VXLAN) {
+ struct vxlanhdr *vxlan_hdr = (struct vxlanhdr *)l2_hdr;
+
+ vxlan_hdr->vx_flags = VXLAN_FLAGS;
+ vxlan_hdr->vx_vni = bpf_htonl((VXLAN_VNI & VXLAN_VNI_MASK) << 8);
+
+ l2_hdr += sizeof(struct vxlanhdr);
+ }
+
+ if (bpf_skb_load_bytes(skb, 0, l2_hdr, ETH_HLEN))
return TC_ACT_SHOT;
break;
}
@@ -372,6 +426,16 @@ int __encap_udp_eth(struct __sk_buff *skb)
return TC_ACT_OK;
}

+SEC("encap_vxlan_eth")
+int __encap_vxlan_eth(struct __sk_buff *skb)
+{
+ if (skb->protocol == __bpf_constant_htons(ETH_P_IP))
+ return encap_ipv4_with_ext_proto(skb, IPPROTO_UDP,
+ ETH_P_TEB, EXTPROTO_VXLAN);
+ else
+ return TC_ACT_OK;
+}
+
SEC("encap_sit_none")
int __encap_sit_none(struct __sk_buff *skb)
{
@@ -444,6 +508,16 @@ int __encap_ip6udp_eth(struct __sk_buff *skb)
return TC_ACT_OK;
}

+SEC("encap_ip6vxlan_eth")
+int __encap_ip6vxlan_eth(struct __sk_buff *skb)
+{
+ if (skb->protocol == __bpf_constant_htons(ETH_P_IPV6))
+ return encap_ipv6_with_ext_proto(skb, IPPROTO_UDP,
+ ETH_P_TEB, EXTPROTO_VXLAN);
+ else
+ return TC_ACT_OK;
+}
+
static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
{
char buf[sizeof(struct v6hdr)];
@@ -479,6 +553,9 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
case ETH_OVER_UDP_PORT:
olen += ETH_HLEN;
break;
+ case VXLAN_UDP_PORT:
+ olen += ETH_HLEN + sizeof(struct vxlanhdr);
+ break;
}
break;
default:
diff --git a/tools/testing/selftests/bpf/test_tc_tunnel.sh b/tools/testing/selftests/bpf/test_tc_tunnel.sh
index 7c76b84..c9dde9b 100755
--- a/tools/testing/selftests/bpf/test_tc_tunnel.sh
+++ b/tools/testing/selftests/bpf/test_tc_tunnel.sh
@@ -44,8 +44,8 @@ setup() {
# clamp route to reserve room for tunnel headers
ip -netns "${ns1}" -4 route flush table main
ip -netns "${ns1}" -6 route flush table main
- ip -netns "${ns1}" -4 route add "${ns2_v4}" mtu 1458 dev veth1
- ip -netns "${ns1}" -6 route add "${ns2_v6}" mtu 1438 dev veth1
+ ip -netns "${ns1}" -4 route add "${ns2_v4}" mtu 1450 dev veth1
+ ip -netns "${ns1}" -6 route add "${ns2_v6}" mtu 1430 dev veth1

sleep 1

@@ -105,6 +105,12 @@ if [[ "$#" -eq "0" ]]; then
echo "sit"
$0 ipv6 sit none 100

+ echo "ip4 vxlan"
+ $0 ipv4 vxlan eth 2000
+
+ echo "ip6 vxlan"
+ $0 ipv6 ip6vxlan eth 2000
+
for mac in none mpls eth ; do
echo "ip gre $mac"
$0 ipv4 gre $mac 100
@@ -214,6 +220,9 @@ if [[ "$tuntype" =~ "udp" ]]; then
targs="encap fou encap-sport auto encap-dport $dport"
elif [[ "$tuntype" =~ "gre" && "$mac" == "eth" ]]; then
ttype=$gretaptype
+elif [[ "$tuntype" =~ "vxlan" && "$mac" == "eth" ]]; then
+ ttype="vxlan"
+ targs="id 1 dstport 8472 udp6zerocsumrx"
else
ttype=$tuntype
targs=""
@@ -242,7 +251,7 @@ if [[ "$tuntype" == "ip6udp" && "$mac" == "mpls" ]]; then
elif [[ "$tuntype" =~ "udp" && "$mac" == "eth" ]]; then
# No support for TEB fou tunnel; expect failure.
expect_tun_fail=1
-elif [[ "$tuntype" =~ "gre" && "$mac" == "eth" ]]; then
+elif [[ "$tuntype" =~ (gre|vxlan) && "$mac" == "eth" ]]; then
# Share ethernet address between tunnel/veth2 so L2 decap works.
ethaddr=$(ip netns exec "${ns2}" ip link show veth2 | \
awk '/ether/ { print $2 }')
--
1.8.3.1