Subject: Re: [PATCH bpf-next v2 18/20] selftests/bpf: Use AF_INET for TX in xdp_metadata

From: Stanislav Fomichev <[email-masked]>
Date: Wed, 5 Jul 2023 10:39:35 -0700

On 07/03, Larysa Zaremba wrote:
> The easiest way to simulate stripped VLAN tag in veth is to send a packet
> from VLAN interface, attached to veth. Unfortunately, this approach is
> incompatible with AF_XDP on TX side, because VLAN interfaces do not have
> such feature.
> 
> Replace AF_XDP packet generation with sending the same datagram via
> AF_INET socket.
> 
> This does not change the packet contents or hints values with one notable
> exception: rx_hash_type, which previously was expected to be 0, now is
> expected be at least XDP_RSS_TYPE_L4.
> 
> Also, usage of AF_INET requires a little more complicated namespace setup,
> therefore open_netns() helper function is divided into smaller reusable
> pieces.

Ack, it's probably OK for now, but, FYI, I'm trying to extend this part
with TX metadata:
https://lore.kernel.org/bpf/[email-masked]/

So probably long-term I'll switch it back to AF_XDP but will add
support for requesting vlan TX "offload" from the veth.
 
> Signed-off-by: Larysa Zaremba <[email-masked]>
> ---
>  tools/testing/selftests/bpf/network_helpers.c |  37 +++-
>  tools/testing/selftests/bpf/network_helpers.h |   3 +
>  .../selftests/bpf/prog_tests/xdp_metadata.c   | 175 +++++++-----------
>  3 files changed, 98 insertions(+), 117 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
> index a105c0cd008a..19463230ece5 100644
> --- a/tools/testing/selftests/bpf/network_helpers.c
> +++ b/tools/testing/selftests/bpf/network_helpers.c
> @@ -386,28 +386,51 @@ char *ping_command(int family)
>  	return "ping";
>  }
>  
> +int get_cur_netns(void)
> +{
> +	int nsfd;
> +
> +	nsfd = open("/proc/self/ns/net", O_RDONLY);
> +	ASSERT_GE(nsfd, 0, "open /proc/self/ns/net");
> +	return nsfd;
> +}
> +
> +int get_netns(const char *name)
> +{
> +	char nspath[PATH_MAX];
> +	int nsfd;
> +
> +	snprintf(nspath, sizeof(nspath), "%s/%s", "/var/run/netns", name);
> +	nsfd = open(nspath, O_RDONLY | O_CLOEXEC);
> +	ASSERT_GE(nsfd, 0, "open /proc/self/ns/net");
> +	return nsfd;
> +}
> +
> +int set_netns(int netns_fd)
> +{
> +	return setns(netns_fd, CLONE_NEWNET);
> +}

We have open_netns/close_netns in network_helpers.h that provide similar
functionality, let's use them instead?

> +
>  struct nstoken {
>  	int orig_netns_fd;
>  };
>  
>  struct nstoken *open_netns(const char *name)
>  {
> +	struct nstoken *token;
>  	int nsfd;
> -	char nspath[PATH_MAX];
>  	int err;
> -	struct nstoken *token;
>  
>  	token = calloc(1, sizeof(struct nstoken));
>  	if (!ASSERT_OK_PTR(token, "malloc token"))
>  		return NULL;
>  
> -	token->orig_netns_fd = open("/proc/self/ns/net", O_RDONLY);
> -	if (!ASSERT_GE(token->orig_netns_fd, 0, "open /proc/self/ns/net"))
> +	token->orig_netns_fd = get_cur_netns();
> +	if (token->orig_netns_fd < 0)
>  		goto fail;
>  
> -	snprintf(nspath, sizeof(nspath), "%s/%s", "/var/run/netns", name);
> -	nsfd = open(nspath, O_RDONLY | O_CLOEXEC);
> -	if (!ASSERT_GE(nsfd, 0, "open netns fd"))
> +	nsfd = get_netns(name);
> +	if (nsfd < 0)
>  		goto fail;
>  
>  	err = setns(nsfd, CLONE_NEWNET);
> diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
> index 694185644da6..b18b9619595c 100644
> --- a/tools/testing/selftests/bpf/network_helpers.h
> +++ b/tools/testing/selftests/bpf/network_helpers.h
> @@ -58,6 +58,8 @@ int make_sockaddr(int family, const char *addr_str, __u16 port,
>  char *ping_command(int family);
>  int get_socket_local_port(int sock_fd);
>  
> +int get_cur_netns(void);
> +int get_netns(const char *name);
>  struct nstoken;
>  /**
>   * open_netns() - Switch to specified network namespace by name.
> @@ -67,4 +69,5 @@ struct nstoken;
>   */
>  struct nstoken *open_netns(const char *name);
>  void close_netns(struct nstoken *token);
> +int set_netns(int netns_fd);
>  #endif
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> index 626c461fa34d..53b32a641e8e 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> @@ -20,7 +20,7 @@
>  
>  #define UDP_PAYLOAD_BYTES 4
>  
> -#define AF_XDP_SOURCE_PORT 1234
> +#define UDP_SOURCE_PORT 1234
>  #define AF_XDP_CONSUMER_PORT 8080
>  
>  #define UMEM_NUM 16
> @@ -33,6 +33,12 @@
>  #define RX_ADDR "10.0.0.2"
>  #define PREFIX_LEN "8"
>  #define FAMILY AF_INET
> +#define TX_NETNS_NAME "xdp_metadata_tx"
> +#define RX_NETNS_NAME "xdp_metadata_rx"
> +#define TX_MAC "00:00:00:00:00:01"
> +#define RX_MAC "00:00:00:00:00:02"
> +
> +#define XDP_RSS_TYPE_L4 BIT(3)
>  
>  struct xsk {
>  	void *umem_area;
> @@ -119,90 +125,28 @@ static void close_xsk(struct xsk *xsk)
>  	munmap(xsk->umem_area, UMEM_SIZE);
>  }
>  
> -static void ip_csum(struct iphdr *iph)
> +static int generate_packet_udp(void)
>  {
> -	__u32 sum = 0;
> -	__u16 *p;
> -	int i;
> -
> -	iph->check = 0;
> -	p = (void *)iph;
> -	for (i = 0; i < sizeof(*iph) / sizeof(*p); i++)
> -		sum += p[i];
> -
> -	while (sum >> 16)
> -		sum = (sum & 0xffff) + (sum >> 16);
> -
> -	iph->check = ~sum;
> -}
> -
> -static int generate_packet(struct xsk *xsk, __u16 dst_port)
> -{
> -	struct xdp_desc *tx_desc;
> -	struct udphdr *udph;
> -	struct ethhdr *eth;
> -	struct iphdr *iph;
> -	void *data;
> -	__u32 idx;
> -	int ret;
> -
> -	ret = xsk_ring_prod__reserve(&xsk->tx, 1, &idx);
> -	if (!ASSERT_EQ(ret, 1, "xsk_ring_prod__reserve"))
> -		return -1;
> -
> -	tx_desc = xsk_ring_prod__tx_desc(&xsk->tx, idx);
> -	tx_desc->addr = idx % (UMEM_NUM / 2) * UMEM_FRAME_SIZE;
> -	printf("%p: tx_desc[%u]->addr=%llx\n", xsk, idx, tx_desc->addr);
> -	data = xsk_umem__get_data(xsk->umem_area, tx_desc->addr);
> -
> -	eth = data;
> -	iph = (void *)(eth + 1);
> -	udph = (void *)(iph + 1);
> -
> -	memcpy(eth->h_dest, "\x00\x00\x00\x00\x00\x02", ETH_ALEN);
> -	memcpy(eth->h_source, "\x00\x00\x00\x00\x00\x01", ETH_ALEN);
> -	eth->h_proto = htons(ETH_P_IP);
> -
> -	iph->version = 0x4;
> -	iph->ihl = 0x5;
> -	iph->tos = 0x9;
> -	iph->tot_len = htons(sizeof(*iph) + sizeof(*udph) + UDP_PAYLOAD_BYTES);
> -	iph->id = 0;
> -	iph->frag_off = 0;
> -	iph->ttl = 0;
> -	iph->protocol = IPPROTO_UDP;
> -	ASSERT_EQ(inet_pton(FAMILY, TX_ADDR, &iph->saddr), 1, "inet_pton(TX_ADDR)");
> -	ASSERT_EQ(inet_pton(FAMILY, RX_ADDR, &iph->daddr), 1, "inet_pton(RX_ADDR)");
> -	ip_csum(iph);
> -
> -	udph->source = htons(AF_XDP_SOURCE_PORT);
> -	udph->dest = htons(dst_port);
> -	udph->len = htons(sizeof(*udph) + UDP_PAYLOAD_BYTES);
> -	udph->check = 0;
> -
> -	memset(udph + 1, 0xAA, UDP_PAYLOAD_BYTES);
> -
> -	tx_desc->len = sizeof(*eth) + sizeof(*iph) + sizeof(*udph) + UDP_PAYLOAD_BYTES;
> -	xsk_ring_prod__submit(&xsk->tx, 1);
> -
> -	ret = sendto(xsk_socket__fd(xsk->socket), NULL, 0, MSG_DONTWAIT, NULL, 0);
> -	if (!ASSERT_GE(ret, 0, "sendto"))
> -		return ret;
> -
> -	return 0;
> -}
> -
> -static void complete_tx(struct xsk *xsk)
> -{
> -	__u32 idx;
> -	__u64 addr;
> -
> -	if (ASSERT_EQ(xsk_ring_cons__peek(&xsk->comp, 1, &idx), 1, "xsk_ring_cons__peek")) {
> -		addr = *xsk_ring_cons__comp_addr(&xsk->comp, idx);
> -
> -		printf("%p: complete tx idx=%u addr=%llx\n", xsk, idx, addr);
> -		xsk_ring_cons__release(&xsk->comp, 1);
> -	}
> +	char udp_payload[UDP_PAYLOAD_BYTES];
> +	struct sockaddr_in rx_addr;
> +	int sock_fd, err = 0;
> +
> +	/* Build a packet */
> +	memset(udp_payload, 0xAA, UDP_PAYLOAD_BYTES);
> +	rx_addr.sin_addr.s_addr = inet_addr(RX_ADDR);
> +	rx_addr.sin_family = AF_INET;
> +	rx_addr.sin_port = htons(UDP_SOURCE_PORT);
> +
> +	sock_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
> +	if (!ASSERT_GE(sock_fd, 0, "socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)"))
> +		return sock_fd;
> +
> +	err = sendto(sock_fd, udp_payload, UDP_PAYLOAD_BYTES, MSG_DONTWAIT,
> +		     (void *)&rx_addr, sizeof(rx_addr));
> +	ASSERT_GE(err, 0, "sendto");
> +
> +	close(sock_fd);
> +	return err;
>  }
>  
>  static void refill_rx(struct xsk *xsk, __u64 addr)
> @@ -268,7 +212,8 @@ static int verify_xsk_metadata(struct xsk *xsk)
>  	if (!ASSERT_NEQ(meta->rx_hash, 0, "rx_hash"))
>  		return -1;
>  
> -	ASSERT_EQ(meta->rx_hash_type, 0, "rx_hash_type");
> +	if (!ASSERT_NEQ(meta->rx_hash_type & XDP_RSS_TYPE_L4, 0, "rx_hash_type"))
> +		return -1;
>  
>  	xsk_ring_cons__release(&xsk->rx, 1);
>  	refill_rx(xsk, comp_addr);
> @@ -281,40 +226,46 @@ void test_xdp_metadata(void)
>  	struct xdp_metadata2 *bpf_obj2 = NULL;
>  	struct xdp_metadata *bpf_obj = NULL;
>  	struct bpf_program *new_prog, *prog;
> -	struct nstoken *tok = NULL;
> +	int prev_netns, rx_netns, tx_netns;
>  	__u32 queue_id = QUEUE_ID;
>  	struct bpf_map *prog_arr;
> -	struct xsk tx_xsk = {};
>  	struct xsk rx_xsk = {};
>  	__u32 val, key = 0;
>  	int retries = 10;
>  	int rx_ifindex;
> -	int tx_ifindex;
>  	int sock_fd;
>  	int ret;
>  
> -	/* Setup new networking namespace, with a veth pair. */
> +	/* Setup new networking namespaces, with a veth pair. */
>  
> -	SYS(out, "ip netns add xdp_metadata");
> -	tok = open_netns("xdp_metadata");
> +	SYS(out, "ip netns add " TX_NETNS_NAME);
> +	SYS(out, "ip netns add " RX_NETNS_NAME);
> +	prev_netns = get_cur_netns();
> +	tx_netns = get_netns(TX_NETNS_NAME);
> +	rx_netns = get_netns(RX_NETNS_NAME);
> +	if (prev_netns < 0 || tx_netns < 0 || rx_netns < 0)
> +		goto close_ns;
> +
> +	set_netns(tx_netns);
>  	SYS(out, "ip link add numtxqueues 1 numrxqueues 1 " TX_NAME
>  	    " type veth peer " RX_NAME " numtxqueues 1 numrxqueues 1");
> -	SYS(out, "ip link set dev " TX_NAME " address 00:00:00:00:00:01");
> -	SYS(out, "ip link set dev " RX_NAME " address 00:00:00:00:00:02");
> +	SYS(out, "ip link set " RX_NAME " netns " RX_NETNS_NAME);
> +
> +	SYS(out, "ip link set dev " TX_NAME " address " TX_MAC);
>  	SYS(out, "ip link set dev " TX_NAME " up");
> -	SYS(out, "ip link set dev " RX_NAME " up");
>  	SYS(out, "ip addr add " TX_ADDR "/" PREFIX_LEN " dev " TX_NAME);
> -	SYS(out, "ip addr add " RX_ADDR "/" PREFIX_LEN " dev " RX_NAME);
>  
> +	/* Avoid ARP calls */
> +	SYS(out, "ip -4 neigh add " RX_ADDR " lladdr " RX_MAC " dev " TX_NAME);
> +
> +	set_netns(rx_netns);
> +	SYS(out, "ip link set dev " RX_NAME " address " RX_MAC);
> +	SYS(out, "ip link set dev " RX_NAME " up");
> +	SYS(out, "ip addr add " RX_ADDR "/" PREFIX_LEN " dev " RX_NAME);
>  	rx_ifindex = if_nametoindex(RX_NAME);
> -	tx_ifindex = if_nametoindex(TX_NAME);
>  
>  	/* Setup separate AF_XDP for TX and RX interfaces. */
>  
> -	ret = open_xsk(tx_ifindex, &tx_xsk);
> -	if (!ASSERT_OK(ret, "open_xsk(TX_NAME)"))
> -		goto out;
> -
>  	ret = open_xsk(rx_ifindex, &rx_xsk);
>  	if (!ASSERT_OK(ret, "open_xsk(RX_NAME)"))
>  		goto out;
> @@ -355,17 +306,16 @@ void test_xdp_metadata(void)
>  		goto out;
>  
>  	/* Send packet destined to RX AF_XDP socket. */
> -	if (!ASSERT_GE(generate_packet(&tx_xsk, AF_XDP_CONSUMER_PORT), 0,
> -		       "generate AF_XDP_CONSUMER_PORT"))
> +	set_netns(tx_netns);
> +	if (!ASSERT_GE(generate_packet_udp(), 0, "generate UDP packet"))
>  		goto out;
>  
>  	/* Verify AF_XDP RX packet has proper metadata. */
> +	set_netns(rx_netns);
>  	if (!ASSERT_GE(verify_xsk_metadata(&rx_xsk), 0,
>  		       "verify_xsk_metadata"))
>  		goto out;
>  
> -	complete_tx(&tx_xsk);
> -
>  	/* Make sure freplace correctly picks up original bound device
>  	 * and doesn't crash.
>  	 */
> @@ -384,10 +334,11 @@ void test_xdp_metadata(void)
>  		goto out;
>  
>  	/* Send packet to trigger . */
> -	if (!ASSERT_GE(generate_packet(&tx_xsk, AF_XDP_CONSUMER_PORT), 0,
> -		       "generate freplace packet"))
> +	set_netns(tx_netns);
> +	if (!ASSERT_GE(generate_packet_udp(), 0, "generate freplace packet"))
>  		goto out;
>  
> +	set_netns(rx_netns);
>  	while (!retries--) {
>  		if (bpf_obj2->bss->called)
>  			break;
> @@ -397,10 +348,14 @@ void test_xdp_metadata(void)
>  
>  out:
>  	close_xsk(&rx_xsk);
> -	close_xsk(&tx_xsk);
>  	xdp_metadata2__destroy(bpf_obj2);
>  	xdp_metadata__destroy(bpf_obj);
> -	if (tok)
> -		close_netns(tok);
> -	SYS_NOFAIL("ip netns del xdp_metadata");
> +	set_netns(prev_netns);
> +close_ns:
> +	close(prev_netns);
> +	close(tx_netns);
> +	close(rx_netns);
> +
> +	SYS_NOFAIL("ip netns del " RX_NETNS_NAME);
> +	SYS_NOFAIL("ip netns del " TX_NETNS_NAME);
>  }
> -- 
> 2.41.0
>