4 files changed, 191 insertions, 1 deletions
diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index 8cf22b3c2563..7f57b916e6b2 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -14,4 +14,5 @@ udpgso_bench_rx
 udpgso_bench_tx
 tcp_inq
 tls
+txring_overwrite
 ip_defrag
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index eec359895feb..7aebbcaa91bf 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -11,7 +11,7 @@ TEST_PROGS += udpgro_bench.sh udpgro.sh
 TEST_PROGS_EXTENDED := in_netns.sh
 TEST_GEN_FILES =  socket
 TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy
-TEST_GEN_FILES += tcp_mmap tcp_inq psock_snd
+TEST_GEN_FILES += tcp_mmap tcp_inq psock_snd txring_overwrite
 TEST_GEN_FILES += udpgso udpgso_bench_tx udpgso_bench_rx ip_defrag
 TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
 TEST_GEN_PROGS += reuseport_dualstack reuseaddr_conflict tls
diff --git a/tools/testing/selftests/net/run_afpackettests b/tools/testing/selftests/net/run_afpackettests
index bea079edc278..2dc95fda7ef7 100755
--- a/tools/testing/selftests/net/run_afpackettests
+++ b/tools/testing/selftests/net/run_afpackettests
@@ -25,3 +25,13 @@ if [ $? -ne 0 ]; then
 else
 	echo "[PASS]"
 fi
+
+echo "--------------------"
+echo "running txring_overwrite test"
+echo "--------------------"
+./in_netns.sh ./txring_overwrite
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+else
+	echo "[PASS]"
+fi
diff --git a/tools/testing/selftests/net/txring_overwrite.c b/tools/testing/selftests/net/txring_overwrite.c
new file mode 100644
index 000000000000..fd8b1c663c39
--- /dev/null
+++ b/tools/testing/selftests/net/txring_overwrite.c
@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Verify that consecutive sends over packet tx_ring are mirrored
+ * with their original content intact.
+ */
+
+#define _GNU_SOURCE
+
+#include <arpa/inet.h>
+#include <assert.h>
+#include <error.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/filter.h>
+#include <linux/if_packet.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/udp.h>
+#include <poll.h>
+#include <pthread.h>
+#include <sched.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+const int eth_off = TPACKET_HDRLEN - sizeof(struct sockaddr_ll);
+const int cfg_frame_size = 1000;
+
+static void build_packet(void *buffer, size_t blen, char payload_char)
+{
+	struct udphdr *udph;
+	struct ethhdr *eth;
+	struct iphdr *iph;
+	size_t off = 0;
+
+	memset(buffer, 0, blen);
+
+	eth = buffer;
+	eth->h_proto = htons(ETH_P_IP);
+
+	off += sizeof(*eth);
+	iph = buffer + off;
+	iph->ttl	= 8;
+	iph->ihl	= 5;
+	iph->version	= 4;
+	iph->saddr	= htonl(INADDR_LOOPBACK);
+	iph->daddr	= htonl(INADDR_LOOPBACK + 1);
+	iph->protocol	= IPPROTO_UDP;
+	iph->tot_len	= htons(blen - off);
+	iph->check	= 0;
+
+	off += sizeof(*iph);
+	udph = buffer + off;
+	udph->dest	= htons(8000);
+	udph->source	= htons(8001);
+	udph->len	= htons(blen - off);
+	udph->check	= 0;
+
+	off += sizeof(*udph);
+	memset(buffer + off, payload_char, blen - off);
+}
+
+static int setup_rx(void)
+{
+	int fdr;
+
+	fdr = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));
+	if (fdr == -1)
+		error(1, errno, "socket r");
+
+	return fdr;
+}
+
+static int setup_tx(char **ring)
+{
+	struct sockaddr_ll laddr = {};
+	struct tpacket_req req = {};
+	int fdt;
+
+	fdt = socket(PF_PACKET, SOCK_RAW, 0);
+	if (fdt == -1)
+		error(1, errno, "socket t");
+
+	laddr.sll_family = AF_PACKET;
+	laddr.sll_protocol = htons(0);
+	laddr.sll_ifindex = if_nametoindex("lo");
+	if (!laddr.sll_ifindex)
+		error(1, errno, "if_nametoindex");
+
+	if (bind(fdt, (void *)&laddr, sizeof(laddr)))
+		error(1, errno, "bind fdt");
+
+	req.tp_block_size = getpagesize();
+	req.tp_block_nr   = 1;
+	req.tp_frame_size = getpagesize();
+	req.tp_frame_nr   = 1;
+
+	if (setsockopt(fdt, SOL_PACKET, PACKET_TX_RING,
+		       (void *)&req, sizeof(req)))
+		error(1, errno, "setsockopt ring");
+
+	*ring = mmap(0, req.tp_block_size * req.tp_block_nr,
+		     PROT_READ | PROT_WRITE, MAP_SHARED, fdt, 0);
+	if (!*ring)
+		error(1, errno, "mmap");
+
+	return fdt;
+}
+
+static void send_pkt(int fdt, void *slot, char payload_char)
+{
+	struct tpacket_hdr *header = slot;
+	int ret;
+
+	while (header->tp_status != TP_STATUS_AVAILABLE)
+		usleep(1000);
+
+	build_packet(slot + eth_off, cfg_frame_size, payload_char);
+
+	header->tp_len = cfg_frame_size;
+	header->tp_status = TP_STATUS_SEND_REQUEST;
+
+	ret = sendto(fdt, NULL, 0, 0, NULL, 0);
+	if (ret == -1)
+		error(1, errno, "kick tx");
+}
+
+static int read_verify_pkt(int fdr, char payload_char)
+{
+	char buf[100];
+	int ret;
+
+	ret = read(fdr, buf, sizeof(buf));
+	if (ret != sizeof(buf))
+		error(1, errno, "read");
+
+	if (buf[60] != payload_char) {
+		printf("wrong pattern: 0x%x != 0x%x\n", buf[60], payload_char);
+		return 1;
+	}
+
+	printf("read: %c (0x%x)\n", buf[60], buf[60]);
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	const char payload_patterns[] = "ab";
+	char *ring;
+	int fdr, fdt, ret = 0;
+
+	fdr = setup_rx();
+	fdt = setup_tx(&ring);
+
+	send_pkt(fdt, ring, payload_patterns[0]);
+	send_pkt(fdt, ring, payload_patterns[1]);
+
+	ret |= read_verify_pkt(fdr, payload_patterns[0]);
+	ret |= read_verify_pkt(fdr, payload_patterns[1]);
+
+	if (close(fdt))
+		error(1, errno, "close t");
+	if (close(fdr))
+		error(1, errno, "close r");
+
+	return ret;
+}