Re: [PATCH net 3/3] selftests: net: tun: test outer protocol of UDP tunnel GSO packets

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Eric Dumazet wrote:
> Add a tun_vnet_udptnl_proto fixture writing single 4in4 Geneve GSO
> frames to a tap device with UDP tunnel offloads enabled:
> 
> - outer_proto_ok: an outer IPv4 header, with or without an 802.1Q tag,
>   is accepted.
> - outer_proto_bad: an outer ethertype that does not match the declared
>   tunnel type (IPv6 on an IPv4 tunnel, or NSH, with or without a VLAN
>   tag) is rejected with EINVAL.
> 
> Without the previous virtio_net patch, outer_proto_bad fails because
> the kernel accepts the frames.
> 
> Signed-off-by: Eric Dumazet <edumazet@kernel.org>
> ---
>  tools/testing/selftests/net/tun.c | 130 ++++++++++++++++++++++++++++++
>  1 file changed, 130 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/tun.c b/tools/testing/selftests/net/tun.c
> index 34de2580e32e..47a24b9c477b 100644
> --- a/tools/testing/selftests/net/tun.c
> +++ b/tools/testing/selftests/net/tun.c
> @@ -683,6 +683,136 @@ TEST_F(tun_vnet_gso, vlan_tcpv4_gso_no_csum_64k)
>  	ASSERT_EQ(ret, len);
>  }
>  
> +#ifndef ETH_P_NSH
> +#define ETH_P_NSH 0x894F
> +#endif
> +
> +FIXTURE(tun_vnet_udptnl_proto)
> +{
> +	char ifname[IFNAMSIZ];
> +	uint8_t *pkt;
> +	int fd;
> +};
> +
> +FIXTURE_SETUP(tun_vnet_udptnl_proto)
> +{
> +	int flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
> +	int features = TUN_F_CSUM | TUN_F_UDP_TUNNEL_GSO |
> +		       TUN_F_UDP_TUNNEL_GSO_CSUM | TUN_F_USO4 | TUN_F_USO6;
> +
> +	self->fd = -1;
> +	if (unshare(CLONE_NEWNET))
> +		SKIP(return, "Cannot create network namespace: %s",
> +		     strerror(errno));
> +
> +	self->pkt = calloc(1, MAX_VNET_TUNNEL_PACKET_SZ);
> +	ASSERT_NE(self->pkt, NULL);
> +
> +	memset(self->ifname, 0, sizeof(self->ifname));
> +	self->fd = tun_open(self->ifname, flags, TUN_VNET_TNL_SIZE, features,
> +			    param_hwaddr_outer_src);
> +	ASSERT_GE(self->fd, 0);
> +}
> +
> +FIXTURE_TEARDOWN(tun_vnet_udptnl_proto)
> +{
> +	if (self->fd >= 0)
> +		close(self->fd);
> +	free(self->pkt);
> +}
> +
> +/* Build a 4in4 Geneve GSO frame whose outer ethertype is @l3proto,
> + * optionally behind an 802.1Q tag.
> + */
> +static int build_udptnl_frame(uint8_t *buf, bool vlan, uint16_t l3proto,
> +			      int payload_len)
> +{
> +	struct virtio_net_hdr_v1_hash_tunnel *vh = (void *)buf;
> +	int vlan_len = vlan ? 4 : 0;
> +	int hlen = ETH_HLEN + vlan_len + UDP_TUNNEL_GENEVE_4IN4_HDRLEN;
> +	uint8_t *outer_udph, *cur = buf;
> +	int pktlen;
> +

zero buffer. It is zeroed by calloc, but reused for multiple packets.

> +	cur += build_virtio_net_hdr_v1_hash_tunnel(cur, true, hlen, 1400,
> +						   AF_INET, AF_INET);
> +	vh->outer_th_offset += vlan_len;
> +	vh->inner_nh_offset += vlan_len;
> +	vh->hash_hdr.hdr.csum_start += vlan_len;
> +
> +	if (vlan) {
> +		uint16_t vlan_tag[2] = { htons(100), htons(l3proto) };
> +
> +		cur += build_eth(cur, ETH_P_8021Q, param_hwaddr_outer_dst,
> +				 param_hwaddr_outer_src);
> +		memcpy(cur, vlan_tag, sizeof(vlan_tag));
> +		cur += sizeof(vlan_tag);
> +	} else {
> +		cur += build_eth(cur, l3proto, param_hwaddr_outer_dst,
> +				 param_hwaddr_outer_src);
> +	}
> +
> +	pktlen = UDP_TUNNEL_GENEVE_4IN4_HDRLEN - sizeof(struct iphdr) +
> +		 payload_len;
> +	cur += build_ipv4_header(cur, IPPROTO_UDP, pktlen,
> +				 &param_ipaddr4_outer_dst,
> +				 &param_ipaddr4_outer_src);
> +
> +	outer_udph = cur;
> +	cur += build_udp_header(cur, UDP_SRC_PORT, VN_PORT,
> +				pktlen - sizeof(struct udphdr));
> +	cur += build_geneve_header(cur, VN_ID);
> +	cur += build_eth(cur, ETH_P_IP, param_hwaddr_inner_dst,
> +			 param_hwaddr_inner_src);
> +	cur += build_ipv4_header(cur, IPPROTO_UDP,
> +				 sizeof(struct udphdr) + payload_len,
> +				 &param_ipaddr4_inner_dst,
> +				 &param_ipaddr4_inner_src);
> +	cur += build_udp_packet(cur, UDP_DST_PORT, UDP_SRC_PORT, payload_len,
> +				AF_INET, false);
> +	build_udp_packet_csum(outer_udph, AF_INET, false);
> +
> +	return cur - buf;
> +}
> +
> +TEST_F(tun_vnet_udptnl_proto, outer_proto_ok)
> +{
> +	uint8_t *pkt = self->pkt;
> +	int len, ret;
> +
> +	len = build_udptnl_frame(pkt, false, ETH_P_IP, 2800);
> +	ret = write(self->fd, pkt, len);
> +	ASSERT_EQ(ret, len);
> +
> +	/* The outer IPv4 header can follow a VLAN tag. */
> +	len = build_udptnl_frame(pkt, true, ETH_P_IP, 2800);
> +	ret = write(self->fd, pkt, len);
> +	ASSERT_EQ(ret, len);
> +}
> +
> +TEST_F(tun_vnet_udptnl_proto, outer_proto_bad)
> +{
> +	uint8_t *pkt = self->pkt;
> +	int len, ret;
> +
> +	/* Outer ethertype does not match the declared IPv4 tunnel. */
> +	len = build_udptnl_frame(pkt, false, ETH_P_IPV6, 2800);
> +	ret = write(self->fd, pkt, len);
> +	ASSERT_EQ(ret, -1);
> +	ASSERT_EQ(errno, EINVAL);
> +
> +	/* Outer header is not IP at all. */
> +	len = build_udptnl_frame(pkt, false, ETH_P_NSH, 2800);
> +	ret = write(self->fd, pkt, len);
> +	ASSERT_EQ(ret, -1);
> +	ASSERT_EQ(errno, EINVAL);
> +
> +	/* Same, behind a VLAN tag. */
> +	len = build_udptnl_frame(pkt, true, ETH_P_NSH, 2800);
> +	ret = write(self->fd, pkt, len);
> +	ASSERT_EQ(ret, -1);
> +	ASSERT_EQ(errno, EINVAL);
> +}
> +
>  FIXTURE(tun_vnet_udptnl)
>  {
>  	char ifname[IFNAMSIZ];
> -- 
> 2.53.0
>