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

From: Larysa Zaremba <[email-masked]>
Date: Thu, 6 Jul 2023 16:11:03 +0200

On Wed, Jul 05, 2023 at 10:39:35AM -0700, Stanislav Fomichev wrote:
> 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.
>

My bad for not reading your series. Amazing work as always!

So, 'requesting vlan TX "offload"' with new hints capabilities? This would be 
pretty neat.

But you think AF_INET TX is worth keeping for now, until TX hints are mature?
  
> > 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?
> 

I have divided open_netns() into smaller pieces (see below), because the code I 
have added into xdp_metadata looked better with those smaller pieces (I had to 
switch namespace several times).

> > +
> >  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
> >