test: add msg_zerocopy test

Introduce regression test for msg_zerocopy feature. Send traffic from
one process to another with and without zerocopy.

Evaluate tcp, udp, raw and packet sockets, including variants
- udp: corking and corking with mixed copy/zerocopy calls
- raw: with and without hdrincl
- packet: at both raw and dgram level

Test on both ipv4 and ipv6, optionally with ethtool changes to
disable scatter-gather, tx checksum or tso offload. All of these
can affect zerocopy behavior.

The regression test can be run on a single machine if over a veth
pair. Then skb_orphan_frags_rx must be modified to be identical to
skb_orphan_frags to allow forwarding zerocopy locally.

The msg_zerocopy.sh script will setup the veth pair in network
namespaces and run all tests.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 811 insertions, 1 deletions

diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index afe109e5508a..9801253e4802 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -1,3 +1,4 @@
+msg_zerocopy
 socket
 psock_fanout
 psock_tpacket
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index f6c9dbf478f8..6135a8448900 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -7,7 +7,7 @@ TEST_PROGS := run_netsocktests run_afpackettests test_bpf.sh netdevice.sh
 TEST_GEN_FILES =  socket
 TEST_GEN_FILES += psock_fanout psock_tpacket
 TEST_GEN_FILES += reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
-TEST_GEN_FILES += reuseport_dualstack
+TEST_GEN_FILES += reuseport_dualstack msg_zerocopy
 
 include ../lib.mk
 
diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
new file mode 100644
index 000000000000..448c69a8af74
--- /dev/null
+++ b/tools/testing/selftests/net/msg_zerocopy.c
@@ -0,0 +1,697 @@
+/* Evaluate MSG_ZEROCOPY
+ *
+ * Send traffic between two processes over one of the supported
+ * protocols and modes:
+ *
+ * PF_INET/PF_INET6
+ * - SOCK_STREAM
+ * - SOCK_DGRAM
+ * - SOCK_DGRAM with UDP_CORK
+ * - SOCK_RAW
+ * - SOCK_RAW with IP_HDRINCL
+ *
+ * PF_PACKET
+ * - SOCK_DGRAM
+ * - SOCK_RAW
+ *
+ * Start this program on two connected hosts, one in send mode and
+ * the other with option '-r' to put it in receiver mode.
+ *
+ * If zerocopy mode ('-z') is enabled, the sender will verify that
+ * the kernel queues completions on the error queue for all zerocopy
+ * transfers.
+ */
+
+#define _GNU_SOURCE
+
+#include <arpa/inet.h>
+#include <error.h>
+#include <errno.h>
+#include <limits.h>
+#include <linux/errqueue.h>
+#include <linux/if_packet.h>
+#include <linux/ipv6.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
+#include <poll.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#ifndef SO_EE_ORIGIN_ZEROCOPY
+#define SO_EE_ORIGIN_ZEROCOPY		SO_EE_ORIGIN_UPAGE
+#endif
+
+#ifndef SO_ZEROCOPY
+#define SO_ZEROCOPY	59
+#endif
+
+#ifndef SO_EE_CODE_ZEROCOPY_COPIED
+#define SO_EE_CODE_ZEROCOPY_COPIED	1
+#endif
+
+#ifndef MSG_ZEROCOPY
+#define MSG_ZEROCOPY	0x4000000
+#endif
+
+static int  cfg_cork;
+static bool cfg_cork_mixed;
+static int  cfg_cpu		= -1;		/* default: pin to last cpu */
+static int  cfg_family		= PF_UNSPEC;
+static int  cfg_ifindex		= 1;
+static int  cfg_payload_len;
+static int  cfg_port		= 8000;
+static bool cfg_rx;
+static int  cfg_runtime_ms	= 4200;
+static int  cfg_verbose;
+static int  cfg_waittime_ms	= 500;
+static bool cfg_zerocopy;
+
+static socklen_t cfg_alen;
+static struct sockaddr_storage cfg_dst_addr;
+static struct sockaddr_storage cfg_src_addr;
+
+static char payload[IP_MAXPACKET];
+static long packets, bytes, completions, expected_completions;
+static int  zerocopied = -1;
+static uint32_t next_completion;
+
+static unsigned long gettimeofday_ms(void)
+{
+	struct timeval tv;
+
+	gettimeofday(&tv, NULL);
+	return (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
+}
+
+static uint16_t get_ip_csum(const uint16_t *start, int num_words)
+{
+	unsigned long sum = 0;
+	int i;
+
+	for (i = 0; i < num_words; i++)
+		sum += start[i];
+
+	while (sum >> 16)
+		sum = (sum & 0xFFFF) + (sum >> 16);
+
+	return ~sum;
+}
+
+static int do_setcpu(int cpu)
+{
+	cpu_set_t mask;
+
+	CPU_ZERO(&mask);
+	CPU_SET(cpu, &mask);
+	if (sched_setaffinity(0, sizeof(mask), &mask))
+		error(1, 0, "setaffinity %d", cpu);
+
+	if (cfg_verbose)
+		fprintf(stderr, "cpu: %u\n", cpu);
+
+	return 0;
+}
+
+static void do_setsockopt(int fd, int level, int optname, int val)
+{
+	if (setsockopt(fd, level, optname, &val, sizeof(val)))
+		error(1, errno, "setsockopt %d.%d: %d", level, optname, val);
+}
+
+static int do_poll(int fd, int events)
+{
+	struct pollfd pfd;
+	int ret;
+
+	pfd.events = events;
+	pfd.revents = 0;
+	pfd.fd = fd;
+
+	ret = poll(&pfd, 1, cfg_waittime_ms);
+	if (ret == -1)
+		error(1, errno, "poll");
+
+	return ret && (pfd.revents & events);
+}
+
+static int do_accept(int fd)
+{
+	int fda = fd;
+
+	fd = accept(fda, NULL, NULL);
+	if (fd == -1)
+		error(1, errno, "accept");
+	if (close(fda))
+		error(1, errno, "close listen sock");
+
+	return fd;
+}
+
+static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy)
+{
+	int ret, len, i, flags;
+
+	len = 0;
+	for (i = 0; i < msg->msg_iovlen; i++)
+		len += msg->msg_iov[i].iov_len;
+
+	flags = MSG_DONTWAIT;
+	if (do_zerocopy)
+		flags |= MSG_ZEROCOPY;
+
+	ret = sendmsg(fd, msg, flags);
+	if (ret == -1 && errno == EAGAIN)
+		return false;
+	if (ret == -1)
+		error(1, errno, "send");
+	if (cfg_verbose && ret != len)
+		fprintf(stderr, "send: ret=%u != %u\n", ret, len);
+
+	if (len) {
+		packets++;
+		bytes += ret;
+		if (do_zerocopy && ret)
+			expected_completions++;
+	}
+
+	return true;
+}
+
+static void do_sendmsg_corked(int fd, struct msghdr *msg)
+{
+	bool do_zerocopy = cfg_zerocopy;
+	int i, payload_len, extra_len;
+
+	/* split up the packet. for non-multiple, make first buffer longer */
+	payload_len = cfg_payload_len / cfg_cork;
+	extra_len = cfg_payload_len - (cfg_cork * payload_len);
+
+	do_setsockopt(fd, IPPROTO_UDP, UDP_CORK, 1);
+
+	for (i = 0; i < cfg_cork; i++) {
+
+		/* in mixed-frags mode, alternate zerocopy and copy frags
+		 * start with non-zerocopy, to ensure attach later works
+		 */
+		if (cfg_cork_mixed)
+			do_zerocopy = (i & 1);
+
+		msg->msg_iov[0].iov_len = payload_len + extra_len;
+		extra_len = 0;
+
+		do_sendmsg(fd, msg, do_zerocopy);
+	}
+
+	do_setsockopt(fd, IPPROTO_UDP, UDP_CORK, 0);
+}
+
+static int setup_iph(struct iphdr *iph, uint16_t payload_len)
+{
+	struct sockaddr_in *daddr = (void *) &cfg_dst_addr;
+	struct sockaddr_in *saddr = (void *) &cfg_src_addr;
+
+	memset(iph, 0, sizeof(*iph));
+
+	iph->version	= 4;
+	iph->tos	= 0;
+	iph->ihl	= 5;
+	iph->ttl	= 2;
+	iph->saddr	= saddr->sin_addr.s_addr;
+	iph->daddr	= daddr->sin_addr.s_addr;
+	iph->protocol	= IPPROTO_EGP;
+	iph->tot_len	= htons(sizeof(*iph) + payload_len);
+	iph->check	= get_ip_csum((void *) iph, iph->ihl << 1);
+
+	return sizeof(*iph);
+}
+
+static int setup_ip6h(struct ipv6hdr *ip6h, uint16_t payload_len)
+{
+	struct sockaddr_in6 *daddr = (void *) &cfg_dst_addr;
+	struct sockaddr_in6 *saddr = (void *) &cfg_src_addr;
+
+	memset(ip6h, 0, sizeof(*ip6h));
+
+	ip6h->version		= 6;
+	ip6h->payload_len	= htons(payload_len);
+	ip6h->nexthdr		= IPPROTO_EGP;
+	ip6h->hop_limit		= 2;
+	ip6h->saddr		= saddr->sin6_addr;
+	ip6h->daddr		= daddr->sin6_addr;
+
+	return sizeof(*ip6h);
+}
+
+static void setup_sockaddr(int domain, const char *str_addr, void *sockaddr)
+{
+	struct sockaddr_in6 *addr6 = (void *) sockaddr;
+	struct sockaddr_in *addr4 = (void *) sockaddr;
+
+	switch (domain) {
+	case PF_INET:
+		addr4->sin_family = AF_INET;
+		addr4->sin_port = htons(cfg_port);
+		if (inet_pton(AF_INET, str_addr, &(addr4->sin_addr)) != 1)
+			error(1, 0, "ipv4 parse error: %s", str_addr);
+		break;
+	case PF_INET6:
+		addr6->sin6_family = AF_INET6;
+		addr6->sin6_port = htons(cfg_port);
+		if (inet_pton(AF_INET6, str_addr, &(addr6->sin6_addr)) != 1)
+			error(1, 0, "ipv6 parse error: %s", str_addr);
+		break;
+	default:
+		error(1, 0, "illegal domain");
+	}
+}
+
+static int do_setup_tx(int domain, int type, int protocol)
+{
+	int fd;
+
+	fd = socket(domain, type, protocol);
+	if (fd == -1)
+		error(1, errno, "socket t");
+
+	do_setsockopt(fd, SOL_SOCKET, SO_SNDBUF, 1 << 21);
+	if (cfg_zerocopy)
+		do_setsockopt(fd, SOL_SOCKET, SO_ZEROCOPY, 1);
+
+	if (domain != PF_PACKET)
+		if (connect(fd, (void *) &cfg_dst_addr, cfg_alen))
+			error(1, errno, "connect");
+
+	return fd;
+}
+
+static bool do_recv_completion(int fd)
+{
+	struct sock_extended_err *serr;
+	struct msghdr msg = {};
+	struct cmsghdr *cm;
+	uint32_t hi, lo, range;
+	int ret, zerocopy;
+	char control[100];
+
+	msg.msg_control = control;
+	msg.msg_controllen = sizeof(control);
+
+	ret = recvmsg(fd, &msg, MSG_ERRQUEUE);
+	if (ret == -1 && errno == EAGAIN)
+		return false;
+	if (ret == -1)
+		error(1, errno, "recvmsg notification");
+	if (msg.msg_flags & MSG_CTRUNC)
+		error(1, errno, "recvmsg notification: truncated");
+
+	cm = CMSG_FIRSTHDR(&msg);
+	if (!cm)
+		error(1, 0, "cmsg: no cmsg");
+	if (!((cm->cmsg_level == SOL_IP && cm->cmsg_type == IP_RECVERR) ||
+	      (cm->cmsg_level == SOL_IPV6 && cm->cmsg_type == IPV6_RECVERR) ||
+	      (cm->cmsg_level == SOL_PACKET && cm->cmsg_type == PACKET_TX_TIMESTAMP)))
+		error(1, 0, "serr: wrong type: %d.%d",
+		      cm->cmsg_level, cm->cmsg_type);
+
+	serr = (void *) CMSG_DATA(cm);
+	if (serr->ee_origin != SO_EE_ORIGIN_ZEROCOPY)
+		error(1, 0, "serr: wrong origin: %u", serr->ee_origin);
+	if (serr->ee_errno != 0)
+		error(1, 0, "serr: wrong error code: %u", serr->ee_errno);
+
+	hi = serr->ee_data;
+	lo = serr->ee_info;
+	range = hi - lo + 1;
+
+	/* Detect notification gaps. These should not happen often, if at all.
+	 * Gaps can occur due to drops, reordering and retransmissions.
+	 */
+	if (lo != next_completion)
+		fprintf(stderr, "gap: %u..%u does not append to %u\n",
+			lo, hi, next_completion);
+	next_completion = hi + 1;
+
+	zerocopy = !(serr->ee_code & SO_EE_CODE_ZEROCOPY_COPIED);
+	if (zerocopied == -1)
+		zerocopied = zerocopy;
+	else if (zerocopied != zerocopy) {
+		fprintf(stderr, "serr: inconsistent\n");
+		zerocopied = zerocopy;
+	}
+
+	if (cfg_verbose >= 2)
+		fprintf(stderr, "completed: %u (h=%u l=%u)\n",
+			range, hi, lo);
+
+	completions += range;
+	return true;
+}
+
+/* Read all outstanding messages on the errqueue */
+static void do_recv_completions(int fd)
+{
+	while (do_recv_completion(fd)) {}
+}
+
+/* Wait for all remaining completions on the errqueue */
+static void do_recv_remaining_completions(int fd)
+{
+	int64_t tstop = gettimeofday_ms() + cfg_waittime_ms;
+
+	while (completions < expected_completions &&
+	       gettimeofday_ms() < tstop) {
+		if (do_poll(fd, POLLERR))
+			do_recv_completions(fd);
+	}
+
+	if (completions < expected_completions)
+		error(1, 0, "missing notifications: %lu < %lu\n",
+		      completions, expected_completions);
+}
+
+static void do_tx(int domain, int type, int protocol)
+{
+	struct iovec iov[3] = { {0} };
+	struct sockaddr_ll laddr;
+	struct msghdr msg = {0};
+	struct ethhdr eth;
+	union {
+		struct ipv6hdr ip6h;
+		struct iphdr iph;
+	} nh;
+	uint64_t tstop;
+	int fd;
+
+	fd = do_setup_tx(domain, type, protocol);
+
+	if (domain == PF_PACKET) {
+		uint16_t proto = cfg_family == PF_INET ? ETH_P_IP : ETH_P_IPV6;
+
+		/* sock_raw passes ll header as data */
+		if (type == SOCK_RAW) {
+			memset(eth.h_dest, 0x06, ETH_ALEN);
+			memset(eth.h_source, 0x02, ETH_ALEN);
+			eth.h_proto = htons(proto);
+			iov[0].iov_base = &eth;
+			iov[0].iov_len = sizeof(eth);
+			msg.msg_iovlen++;
+		}
+
+		/* both sock_raw and sock_dgram expect name */
+		memset(&laddr, 0, sizeof(laddr));
+		laddr.sll_family	= AF_PACKET;
+		laddr.sll_ifindex	= cfg_ifindex;
+		laddr.sll_protocol	= htons(proto);
+		laddr.sll_halen		= ETH_ALEN;
+
+		memset(laddr.sll_addr, 0x06, ETH_ALEN);
+
+		msg.msg_name		= &laddr;
+		msg.msg_namelen		= sizeof(laddr);
+	}
+
+	/* packet and raw sockets with hdrincl must pass network header */
+	if (domain == PF_PACKET || protocol == IPPROTO_RAW) {
+		if (cfg_family == PF_INET)
+			iov[1].iov_len = setup_iph(&nh.iph, cfg_payload_len);
+		else
+			iov[1].iov_len = setup_ip6h(&nh.ip6h, cfg_payload_len);
+
+		iov[1].iov_base = (void *) &nh;
+		msg.msg_iovlen++;
+	}
+
+	iov[2].iov_base = payload;
+	iov[2].iov_len = cfg_payload_len;
+	msg.msg_iovlen++;
+	msg.msg_iov = &iov[3 - msg.msg_iovlen];
+
+	tstop = gettimeofday_ms() + cfg_runtime_ms;
+	do {
+		if (cfg_cork)
+			do_sendmsg_corked(fd, &msg);
+		else
+			do_sendmsg(fd, &msg, cfg_zerocopy);
+
+		while (!do_poll(fd, POLLOUT)) {
+			if (cfg_zerocopy)
+				do_recv_completions(fd);
+		}
+
+	} while (gettimeofday_ms() < tstop);
+
+	if (cfg_zerocopy)
+		do_recv_remaining_completions(fd);
+
+	if (close(fd))
+		error(1, errno, "close");
+
+	fprintf(stderr, "tx=%lu (%lu MB) txc=%lu zc=%c\n",
+		packets, bytes >> 20, completions,
+		zerocopied == 1 ? 'y' : 'n');
+}
+
+static int do_setup_rx(int domain, int type, int protocol)
+{
+	int fd;
+
+	/* If tx over PF_PACKET, rx over PF_INET(6)/SOCK_RAW,
+	 * to recv the only copy of the packet, not a clone
+	 */
+	if (domain == PF_PACKET)
+		error(1, 0, "Use PF_INET/SOCK_RAW to read");
+
+	if (type == SOCK_RAW && protocol == IPPROTO_RAW)
+		error(1, 0, "IPPROTO_RAW: not supported on Rx");
+
+	fd = socket(domain, type, protocol);
+	if (fd == -1)
+		error(1, errno, "socket r");
+
+	do_setsockopt(fd, SOL_SOCKET, SO_RCVBUF, 1 << 21);
+	do_setsockopt(fd, SOL_SOCKET, SO_RCVLOWAT, 1 << 16);
+	do_setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, 1);
+
+	if (bind(fd, (void *) &cfg_dst_addr, cfg_alen))
+		error(1, errno, "bind");
+
+	if (type == SOCK_STREAM) {
+		if (listen(fd, 1))
+			error(1, errno, "listen");
+		fd = do_accept(fd);
+	}
+
+	return fd;
+}
+
+/* Flush all outstanding bytes for the tcp receive queue */
+static void do_flush_tcp(int fd)
+{
+	int ret;
+
+	/* MSG_TRUNC flushes up to len bytes */
+	ret = recv(fd, NULL, 1 << 21, MSG_TRUNC | MSG_DONTWAIT);
+	if (ret == -1 && errno == EAGAIN)
+		return;
+	if (ret == -1)
+		error(1, errno, "flush");
+	if (!ret)
+		return;
+
+	packets++;
+	bytes += ret;
+}
+
+/* Flush all outstanding datagrams. Verify first few bytes of each. */
+static void do_flush_datagram(int fd, int type)
+{
+	int ret, off = 0;
+	char buf[64];
+
+	/* MSG_TRUNC will return full datagram length */
+	ret = recv(fd, buf, sizeof(buf), MSG_DONTWAIT | MSG_TRUNC);
+	if (ret == -1 && errno == EAGAIN)
+		return;
+
+	/* raw ipv4 return with header, raw ipv6 without */
+	if (cfg_family == PF_INET && type == SOCK_RAW) {
+		off += sizeof(struct iphdr);
+		ret -= sizeof(struct iphdr);
+	}
+
+	if (ret == -1)
+		error(1, errno, "recv");
+	if (ret != cfg_payload_len)
+		error(1, 0, "recv: ret=%u != %u", ret, cfg_payload_len);
+	if (ret > sizeof(buf) - off)
+		ret = sizeof(buf) - off;
+	if (memcmp(buf + off, payload, ret))
+		error(1, 0, "recv: data mismatch");
+
+	packets++;
+	bytes += cfg_payload_len;
+}
+
+static void do_rx(int domain, int type, int protocol)
+{
+	uint64_t tstop;
+	int fd;
+
+	fd = do_setup_rx(domain, type, protocol);
+
+	tstop = gettimeofday_ms() + cfg_runtime_ms;
+	do {
+		if (type == SOCK_STREAM)
+			do_flush_tcp(fd);
+		else
+			do_flush_datagram(fd, type);
+
+		do_poll(fd, POLLIN);
+
+	} while (gettimeofday_ms() < tstop);
+
+	if (close(fd))
+		error(1, errno, "close");
+
+	fprintf(stderr, "rx=%lu (%lu MB)\n", packets, bytes >> 20);
+}
+
+static void do_test(int domain, int type, int protocol)
+{
+	int i;
+
+	if (cfg_cork && (domain == PF_PACKET || type != SOCK_DGRAM))
+		error(1, 0, "can only cork udp sockets");
+
+	do_setcpu(cfg_cpu);
+
+	for (i = 0; i < IP_MAXPACKET; i++)
+		payload[i] = 'a' + (i % 26);
+
+	if (cfg_rx)
+		do_rx(domain, type, protocol);
+	else
+		do_tx(domain, type, protocol);
+}
+
+static void usage(const char *filepath)
+{
+	error(1, 0, "Usage: %s [options] <test>", filepath);
+}
+
+static void parse_opts(int argc, char **argv)
+{
+	const int max_payload_len = sizeof(payload) -
+				    sizeof(struct ipv6hdr) -
+				    sizeof(struct tcphdr) -
+				    40 /* max tcp options */;
+	int c;
+
+	cfg_payload_len = max_payload_len;
+
+	while ((c = getopt(argc, argv, "46c:C:D:i:mp:rs:S:t:vz")) != -1) {
+		switch (c) {
+		case '4':
+			if (cfg_family != PF_UNSPEC)
+				error(1, 0, "Pass one of -4 or -6");
+			cfg_family = PF_INET;
+			cfg_alen = sizeof(struct sockaddr_in);
+			break;
+		case '6':
+			if (cfg_family != PF_UNSPEC)
+				error(1, 0, "Pass one of -4 or -6");
+			cfg_family = PF_INET6;
+			cfg_alen = sizeof(struct sockaddr_in6);
+			break;
+		case 'c':
+			cfg_cork = strtol(optarg, NULL, 0);
+			break;
+		case 'C':
+			cfg_cpu = strtol(optarg, NULL, 0);
+			break;
+		case 'D':
+			setup_sockaddr(cfg_family, optarg, &cfg_dst_addr);
+			break;
+		case 'i':
+			cfg_ifindex = if_nametoindex(optarg);
+			if (cfg_ifindex == 0)
+				error(1, errno, "invalid iface: %s", optarg);
+			break;
+		case 'm':
+			cfg_cork_mixed = true;
+			break;
+		case 'p':
+			cfg_port = htons(strtoul(optarg, NULL, 0));
+			break;
+		case 'r':
+			cfg_rx = true;
+			break;
+		case 's':
+			cfg_payload_len = strtoul(optarg, NULL, 0);
+			break;
+		case 'S':
+			setup_sockaddr(cfg_family, optarg, &cfg_src_addr);
+			break;
+		case 't':
+			cfg_runtime_ms = 200 + strtoul(optarg, NULL, 10) * 1000;
+			break;
+		case 'v':
+			cfg_verbose++;
+			break;
+		case 'z':
+			cfg_zerocopy = true;
+			break;
+		}
+	}
+
+	if (cfg_payload_len > max_payload_len)
+		error(1, 0, "-s: payload exceeds max (%d)", max_payload_len);
+	if (cfg_cork_mixed && (!cfg_zerocopy || !cfg_cork))
+		error(1, 0, "-m: cork_mixed requires corking and zerocopy");
+
+	if (optind != argc - 1)
+		usage(argv[0]);
+}
+
+int main(int argc, char **argv)
+{
+	const char *cfg_test;
+
+	parse_opts(argc, argv);
+
+	cfg_test = argv[argc - 1];
+
+	if (!strcmp(cfg_test, "packet"))
+		do_test(PF_PACKET, SOCK_RAW, 0);
+	else if (!strcmp(cfg_test, "packet_dgram"))
+		do_test(PF_PACKET, SOCK_DGRAM, 0);
+	else if (!strcmp(cfg_test, "raw"))
+		do_test(cfg_family, SOCK_RAW, IPPROTO_EGP);
+	else if (!strcmp(cfg_test, "raw_hdrincl"))
+		do_test(cfg_family, SOCK_RAW, IPPROTO_RAW);
+	else if (!strcmp(cfg_test, "tcp"))
+		do_test(cfg_family, SOCK_STREAM, 0);
+	else if (!strcmp(cfg_test, "udp"))
+		do_test(cfg_family, SOCK_DGRAM, 0);
+	else
+		error(1, 0, "unknown cfg_test %s", cfg_test);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
new file mode 100755
index 000000000000..d571d213418d
--- /dev/null
+++ b/tools/testing/selftests/net/msg_zerocopy.sh
@@ -0,0 +1,112 @@
+#!/bin/bash
+#
+# Send data between two processes across namespaces
+# Run twice: once without and once with zerocopy
+
+set -e
+
+readonly DEV="veth0"
+readonly DEV_MTU=65535
+readonly BIN="./msg_zerocopy"
+
+readonly RAND="$(mktemp -u XXXXXX)"
+readonly NSPREFIX="ns-${RAND}"
+readonly NS1="${NSPREFIX}1"
+readonly NS2="${NSPREFIX}2"
+
+readonly SADDR4='192.168.1.1'
+readonly DADDR4='192.168.1.2'
+readonly SADDR6='fd::1'
+readonly DADDR6='fd::2'
+
+readonly path_sysctl_mem="net.core.optmem_max"
+
+# Argument parsing
+if [[ "$#" -lt "2" ]]; then
+	echo "Usage: $0 [4|6] [tcp|udp|raw|raw_hdrincl|packet|packet_dgram] <args>"
+	exit 1
+fi
+
+readonly IP="$1"
+shift
+readonly TXMODE="$1"
+shift
+readonly EXTRA_ARGS="$@"
+
+# Argument parsing: configure addresses
+if [[ "${IP}" == "4" ]]; then
+	readonly SADDR="${SADDR4}"
+	readonly DADDR="${DADDR4}"
+elif [[ "${IP}" == "6" ]]; then
+	readonly SADDR="${SADDR6}"
+	readonly DADDR="${DADDR6}"
+else
+	echo "Invalid IP version ${IP}"
+	exit 1
+fi
+
+# Argument parsing: select receive mode
+#
+# This differs from send mode for
+# - packet:	use raw recv, because packet receives skb clones
+# - raw_hdrinc: use raw recv, because hdrincl is a tx-only option
+case "${TXMODE}" in
+'packet' | 'packet_dgram' | 'raw_hdrincl')
+	RXMODE='raw'
+	;;
+*)
+	RXMODE="${TXMODE}"
+	;;
+esac
+
+# Start of state changes: install cleanup handler
+save_sysctl_mem="$(sysctl -n ${path_sysctl_mem})"
+
+cleanup() {
+	ip netns del "${NS2}"
+	ip netns del "${NS1}"
+	sysctl -w -q "${path_sysctl_mem}=${save_sysctl_mem}"
+}
+
+trap cleanup EXIT
+
+# Configure system settings
+sysctl -w -q "${path_sysctl_mem}=1000000"
+
+# Create virtual ethernet pair between network namespaces
+ip netns add "${NS1}"
+ip netns add "${NS2}"
+
+ip link add "${DEV}" mtu "${DEV_MTU}" netns "${NS1}" type veth \
+  peer name "${DEV}" mtu "${DEV_MTU}" netns "${NS2}"
+
+# Bring the devices up
+ip -netns "${NS1}" link set "${DEV}" up
+ip -netns "${NS2}" link set "${DEV}" up
+
+# Set fixed MAC addresses on the devices
+ip -netns "${NS1}" link set dev "${DEV}" address 02:02:02:02:02:02
+ip -netns "${NS2}" link set dev "${DEV}" address 06:06:06:06:06:06
+
+# Add fixed IP addresses to the devices
+ip -netns "${NS1}" addr add 192.168.1.1/24 dev "${DEV}"
+ip -netns "${NS2}" addr add 192.168.1.2/24 dev "${DEV}"
+ip -netns "${NS1}" addr add       fd::1/64 dev "${DEV}" nodad
+ip -netns "${NS2}" addr add       fd::2/64 dev "${DEV}" nodad
+
+# Optionally disable sg or csum offload to test edge cases
+# ip netns exec "${NS1}" ethtool -K "${DEV}" sg off
+
+do_test() {
+	local readonly ARGS="$1"
+
+	echo "ipv${IP} ${TXMODE} ${ARGS}"
+	ip netns exec "${NS2}" "${BIN}" "-${IP}" -i "${DEV}" -t 2 -C 2 -S "${SADDR}" -D "${DADDR}" ${ARGS} -r "${RXMODE}" &
+	sleep 0.2
+	ip netns exec "${NS1}" "${BIN}" "-${IP}" -i "${DEV}" -t 1 -C 3 -S "${SADDR}" -D "${DADDR}" ${ARGS} "${TXMODE}"
+	wait
+}
+
+do_test "${EXTRA_ARGS}"
+do_test "-z ${EXTRA_ARGS}"
+echo ok