Update XDP, filter out packets not sent on the correct port

.gitignore

 *.o
+*.ll
 *.d
 latency-measure/build/main
 latency-measure/build/main

clockres/src/clockres.c

@@ -45,6 +45,21 @@ static inline uint64_t calcdiff_ns(struct timespec t1, struct timespec t2);
 static inline uint64_t max(uint64_t a, uint64_t b);
 static inline uint64_t min(uint64_t a, uint64_t b);
 
+static void help(char *argv[]) {
+  printf(
+      "Usage: %s [-a CPU -p PRIO -i USEC -r USEC -s NS -l N -v]\n\n"
+      "       -h                 Show help\n"
+      "       -a CPU             Pin the real time thread to CPU\n"
+      "       -p PRIO            RT thread priority\n"
+      "       -i USEC            RT thread wake-up interval (default: 10ms)\n"
+      "       -r USEC            non-RT main thread refresh interval\n"
+      "       -l N_CYCLES        RT thread cycles amount (default: infinite)\n"
+      "       -f                 Trace\n"
+      "       -g                 Use function_graph when tracing\n"
+      "\n",
+      argv[0]);
+}
+
 // Real-time thread
 static void *timerthread(void *p) {
   struct timespec previous, current, next;
@@ -174,11 +189,15 @@ int main(int argc, char *argv[]) {
 static void process_options(int argc, char *argv[], thread_param_t *param,
                             main_param_t *main_param) {
   for (;;) {
-    int c = getopt(argc, argv, "l:p:i:r:f:ag");
+    int c = getopt(argc, argv, "hl:p:i:r:f:ag");
 
     if (c == -1) break;
 
     switch (c) {
+      case 'h':
+        help(argv);
+        exit(EXIT_SUCCESS);
+        break;
       case 'p':
         param->priority = atoi(optarg);
         break;
@@ -202,6 +221,7 @@ static void process_options(int argc, char *argv[], thread_param_t *param,
         main_param->enable_graph = 1;
         break;
       default:
+        help(argv);
         exit(EXIT_FAILURE);
         break;
     }

packet-exchange/src/bpf_endian.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copied from $(LINUX)/tools/testing/selftests/bpf/bpf_endian.h */
+#ifndef __BPF_ENDIAN__
+#define __BPF_ENDIAN__
+
+#include <linux/swab.h>
+
+/* LLVM's BPF target selects the endianness of the CPU
+ * it compiles on, or the user specifies (bpfel/bpfeb),
+ * respectively. The used __BYTE_ORDER__ is defined by
+ * the compiler, we cannot rely on __BYTE_ORDER from
+ * libc headers, since it doesn't reflect the actual
+ * requested byte order.
+ *
+ * Note, LLVM's BPF target has different __builtin_bswapX()
+ * semantics. It does map to BPF_ALU | BPF_END | BPF_TO_BE
+ * in bpfel and bpfeb case, which means below, that we map
+ * to cpu_to_be16(). We could use it unconditionally in BPF
+ * case, but better not rely on it, so that this header here
+ * can be used from application and BPF program side, which
+ * use different targets.
+ */
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+# define __bpf_ntohs(x)__builtin_bswap16(x)
+# define __bpf_htons(x)__builtin_bswap16(x)
+# define __bpf_constant_ntohs(x)___constant_swab16(x)
+# define __bpf_constant_htons(x)___constant_swab16(x)
+# define __bpf_ntohl(x)__builtin_bswap32(x)
+# define __bpf_htonl(x)__builtin_bswap32(x)
+# define __bpf_constant_ntohl(x)___constant_swab32(x)
+# define __bpf_constant_htonl(x)___constant_swab32(x)
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+# define __bpf_ntohs(x)(x)
+# define __bpf_htons(x)(x)
+# define __bpf_constant_ntohs(x)(x)
+# define __bpf_constant_htons(x)(x)
+# define __bpf_ntohl(x)(x)
+# define __bpf_htonl(x)(x)
+# define __bpf_constant_ntohl(x)(x)
+# define __bpf_constant_htonl(x)(x)
+#else
+# error "Fix your compiler's __BYTE_ORDER__?!"
+#endif
+
+#define bpf_htons(x)\
+  (__builtin_constant_p(x) ?\
+   __bpf_constant_htons(x) : __bpf_htons(x))
+#define bpf_ntohs(x)\
+  (__builtin_constant_p(x) ?\
+   __bpf_constant_ntohs(x) : __bpf_ntohs(x))
+#define bpf_htonl(x)\
+  (__builtin_constant_p(x) ?\
+   __bpf_constant_htonl(x) : __bpf_htonl(x))
+#define bpf_ntohl(x)\
+  (__builtin_constant_p(x) ?\
+   __bpf_constant_ntohl(x) : __bpf_ntohl(x))
+
+#endif /* __BPF_ENDIAN__ */
+

packet-exchange/src/client.c

@@ -166,6 +166,8 @@ static void *packet_sending_thread(void *p) {
     }
   }
 
+  printf("Will start at %" PRIu64 "\n", ts_to_uint(next));
+
   // Packet sending loop
   for (nb_cycles = 0;; nb_cycles++) {
     if (thread_params.max_cycles &&

packet-exchange/src/common.c

@@ -82,6 +82,14 @@ void add_ns(struct timespec *t, uint64_t ns) {
     t->tv_nsec -= NSEC_PER_SEC;
   }
 }
+void substract_ns(struct timespec *t, uint64_t ns) {
+  t->tv_nsec -= ns;
+
+  while (t->tv_nsec < 0) {
+    t->tv_sec -= 1;
+    t->tv_nsec += NSEC_PER_SEC;
+  }
+}
 
 uint64_t calcdiff_ns(struct timespec t1, struct timespec t2) {
   uint64_t diff;
@@ -89,6 +97,12 @@ uint64_t calcdiff_ns(struct timespec t1, struct timespec t2) {
   diff += ((int)t1.tv_nsec - (int)t2.tv_nsec);
   return diff;
 }
+int64_t calcdiff_ns_signed(struct timespec t1, struct timespec t2) {
+  int64_t diff;
+  diff = NSEC_PER_SEC * ((int)t1.tv_sec - (int)t2.tv_sec);
+  diff += ((int)t1.tv_nsec - (int)t2.tv_nsec);
+  return diff;
+}
 
 int _max_(int a, int b) { return a > b ? a : b; }
 int _min_(int a, int b) { return a < b ? a : b; }

packet-exchange/src/common.h

@@ -41,7 +41,9 @@
 uint64_t ts_to_uint(struct timespec t);
 struct timespec uint_to_ts(uint64_t t);
 void add_ns(struct timespec *t, uint64_t ns);
+void substract_ns(struct timespec *t, uint64_t ns);
 uint64_t calcdiff_ns(struct timespec t1, struct timespec t2);
+int64_t calcdiff_ns_signed(struct timespec t1, struct timespec t2);
 
 void set_latency_target(void);
 void init_signals(void (*_sighand)(int));

packet-exchange/src/parsing_helpers.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This file contains parsing functions that are used in the packetXX XDP
+ * programs. The functions are marked as __always_inline, and fully defined in
+ * this header file to be included in the BPF program.
+ *
+ * Each helper parses a packet header, including doing bounds checking, and
+ * returns the type of its contents if successful, and -1 otherwise.
+ *
+ * For Ethernet and IP headers, the content type is the type of the payload
+ * (h_proto for Ethernet, nexthdr for IPv6), for ICMP it is the ICMP type field.
+ * All return values are in host byte order.
+ *
+ * The versions of the functions included here are slightly expanded versions of
+ * the functions in the packet01 lesson. For instance, the Ethernet header
+ * parsing has support for parsing VLAN tags.
+ */
+
+#ifndef __PARSING_HELPERS_H
+#define __PARSING_HELPERS_H
+
+#include <stddef.h>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/icmp.h>
+#include <linux/icmpv6.h>
+#include <linux/udp.h>
+#include <linux/tcp.h>
+
+/* Header cursor to keep track of current parsing position */
+struct hdr_cursor {
+	void *pos;
+};
+
+/*
+ *	struct vlan_hdr - vlan header
+ *	@h_vlan_TCI: priority and VLAN ID
+ *	@h_vlan_encapsulated_proto: packet type ID or len
+ */
+struct vlan_hdr {
+	__be16	h_vlan_TCI;
+	__be16	h_vlan_encapsulated_proto;
+};
+
+/*
+ * Struct icmphdr_common represents the common part of the icmphdr and icmp6hdr
+ * structures.
+ */
+struct icmphdr_common {
+	__u8		type;
+	__u8		code;
+	__sum16	cksum;
+};
+
+/* Allow users of header file to redefine VLAN max depth */
+#ifndef VLAN_MAX_DEPTH
+#define VLAN_MAX_DEPTH 4
+#endif
+
+static __always_inline int proto_is_vlan(__u16 h_proto)
+{
+	return !!(h_proto == bpf_htons(ETH_P_8021Q) ||
+		  h_proto == bpf_htons(ETH_P_8021AD));
+}
+
+/* Notice, parse_ethhdr() will skip VLAN tags, by advancing nh->pos and returns
+ * next header EtherType, BUT the ethhdr pointer supplied still points to the
+ * Ethernet header. Thus, caller can look at eth->h_proto to see if this was a
+ * VLAN tagged packet.
+ */
+static __always_inline int parse_ethhdr(struct hdr_cursor *nh, void *data_end,
+					struct ethhdr **ethhdr)
+{
+	struct ethhdr *eth = nh->pos;
+	int hdrsize = sizeof(*eth);
+	struct vlan_hdr *vlh;
+	__u16 h_proto;
+	int i;
+
+	/* Byte-count bounds check; check if current pointer + size of header
+	 * is after data_end.
+	 */
+	if (nh->pos + hdrsize > data_end)
+		return -1;
+
+	nh->pos += hdrsize;
+	*ethhdr = eth;
+	vlh = nh->pos;
+	h_proto = eth->h_proto;
+
+	/* Use loop unrolling to avoid the verifier restriction on loops;
+	 * support up to VLAN_MAX_DEPTH layers of VLAN encapsulation.
+	 */
+	#pragma unroll
+	for (i = 0; i < VLAN_MAX_DEPTH; i++) {
+		if (!proto_is_vlan(h_proto))
+			break;
+
+		if (vlh + 1 > data_end)
+			break;
+
+		h_proto = vlh->h_vlan_encapsulated_proto;
+		vlh++;
+	}
+
+	nh->pos = vlh;
+	return h_proto; /* network-byte-order */
+}
+
+static __always_inline int parse_ip6hdr(struct hdr_cursor *nh,
+					void *data_end,
+					struct ipv6hdr **ip6hdr)
+{
+	struct ipv6hdr *ip6h = nh->pos;
+
+	/* Pointer-arithmetic bounds check; pointer +1 points to after end of
+	 * thing being pointed to. We will be using this style in the remainder
+	 * of the tutorial.
+	 */
+	if (ip6h + 1 > data_end)
+		return -1;
+
+	nh->pos = ip6h + 1;
+	*ip6hdr = ip6h;
+
+	return ip6h->nexthdr;
+}
+
+static __always_inline int parse_iphdr(struct hdr_cursor *nh,
+				       void *data_end,
+				       struct iphdr **iphdr)
+{
+	struct iphdr *iph = nh->pos;
+	int hdrsize;
+
+	if (iph + 1 > data_end)
+		return -1;
+
+	hdrsize = iph->ihl * 4;
+
+	/* Variable-length IPv4 header, need to use byte-based arithmetic */
+	if (nh->pos + hdrsize > data_end)
+		return -1;
+
+	nh->pos += hdrsize;
+	*iphdr = iph;
+
+	return iph->protocol;
+}
+
+static __always_inline int parse_icmp6hdr(struct hdr_cursor *nh,
+					  void *data_end,
+					  struct icmp6hdr **icmp6hdr)
+{
+	struct icmp6hdr *icmp6h = nh->pos;
+
+	if (icmp6h + 1 > data_end)
+		return -1;
+
+	nh->pos   = icmp6h + 1;
+	*icmp6hdr = icmp6h;
+
+	return icmp6h->icmp6_type;
+}
+
+static __always_inline int parse_icmphdr(struct hdr_cursor *nh,
+					 void *data_end,
+					 struct icmphdr **icmphdr)
+{
+	struct icmphdr *icmph = nh->pos;
+
+	if (icmph + 1 > data_end)
+		return -1;
+
+	nh->pos  = icmph + 1;
+	*icmphdr = icmph;
+
+	return icmph->type;
+}
+
+static __always_inline int parse_icmphdr_common(struct hdr_cursor *nh,
+						void *data_end,
+						struct icmphdr_common **icmphdr)
+{
+	struct icmphdr_common *h = nh->pos;
+
+	if (h + 1 > data_end)
+		return -1;
+
+	nh->pos  = h + 1;
+	*icmphdr = h;
+
+	return h->type;
+}
+
+/*
+ * parse_tcphdr: parse the udp header and return the length of the udp payload
+ */
+static __always_inline int parse_udphdr(struct hdr_cursor *nh,
+					void *data_end,
+					struct udphdr **udphdr)
+{
+	int len;
+	struct udphdr *h = nh->pos;
+
+	if (h + 1 > data_end)
+		return -1;
+
+	nh->pos  = h + 1;
+	*udphdr = h;
+
+	len = bpf_ntohs(h->len) - sizeof(struct udphdr);
+	if (len < 0)
+		return -1;
+
+	return len;
+}
+
+/*
+ * parse_tcphdr: parse and return the length of the tcp header
+ */
+static __always_inline int parse_tcphdr(struct hdr_cursor *nh,
+					void *data_end,
+					struct tcphdr **tcphdr)
+{
+	int len;
+	struct tcphdr *h = nh->pos;
+
+	if (h + 1 > data_end)
+		return -1;
+
+	len = h->doff * 4;
+	if ((void *) h + len > data_end)
+		return -1;
+
+	nh->pos  = h + 1;
+	*tcphdr = h;
+
+	return len;
+}
+
+#endif /* __PARSING_HELPERS_H */

packet-exchange/src/recv_packet.c

@@ -256,11 +256,11 @@ static void open_xdp_socket(char *network_if) {
 /*
  * Init XDP socket
  */
-void init_xdp_recv(ingress_param_t * _params) {
+void init_xdp_recv(ingress_param_t * _params, ingress_stat_t *_stats) {
 	int ret, prog_fd, xsks_map = 0;
 	struct bpf_prog_load_attr prog_load_attr = {
 	    .prog_type = BPF_PROG_TYPE_XDP,
-	    .file = "/home/oli/rt-measures/packet-exchange/build/xdp_kern.o",
+	    .file = "/home/oli/tsn-measures/packet-exchange/build/xdp_kern.o",
 	};
 	struct xsk_umem_config cfg = {
 	    .fill_size = XSK_RING_PROD__DEFAULT_NUM_DESCS,
@@ -274,6 +274,7 @@ void init_xdp_recv(ingress_param_t * _params) {
 	void *buffer = NULL;
 
 	params = _params;
+	stats = _stats;
 
 	ret = bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd);
 	if (ret || prog_fd < 0) err("bpf_prog_load_xattr() failed");
@@ -312,11 +313,55 @@ void setup_poll_fd(void) {
 static int received;
 static uint32_t idx_rx = 0, idx;
 
+static void poll_wakeup(struct timespec ts, int margin) {
+  int ret;
+  struct timespec ts_prev, current;
+
+  ts_prev = ts;
+  substract_ns(&ts_prev, margin * 1000);
+
+  ret = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts_prev, NULL);
+  if (ret) {
+    fprintf(stderr, "clock_nanosleep returned error: %d, aborting...\n", ret);
+    exit(EXIT_FAILURE);
+  }
+
+  do {
+    clock_gettime(CLOCK_REALTIME, &current);
+  } while(calcdiff_ns_signed(ts, current) > 1000);
+}
+
+static void parse_raw_packet(uint64_t addr, size_t len)
+{
+    char *packet;
+    struct ethhdr *eth;
+    struct iphdr *ip;
+    struct udphdr *udp;
+    size_t min_len = sizeof(*eth) + sizeof(*ip) + sizeof(*udp);
+
+    if (len <= min_len) {
+      stats->xdp_data = NULL;
+        return;
+    }
+
+    packet = xsk_umem__get_data(xdp_socket.umem.buffer, addr);
+
+    eth = (struct ethhdr *)packet;
+    ip  = (struct iphdr *)(packet + sizeof(*eth));
+    udp = (struct udphdr *)(packet + sizeof(*eth) + sizeof(*ip));
+
+    stats->xdp_data = packet + sizeof(*eth) + sizeof(*ip) + sizeof(*udp);
+}
+
 /*
  * Receive XDP socket
  */
-int recv_xdp_packet(void) {
+int recv_xdp_packet(struct timespec next) {
 	int ret;
+        uint64_t addr;
+        uint32_t len;
+        struct timespec next_pre, current;
+        int k = 0;
 
 	if (params->xdp_polling_mode == 0) {
 		ret = poll(fds, 1, -1);
@@ -327,17 +372,31 @@ int recv_xdp_packet(void) {
 			error(EXIT_FAILURE, errno, "poll failed");
 		received = xsk_ring_cons__peek(&xdp_socket.rx, 1, &idx_rx);
 	} else {
-		do {
-			received =
-			    xsk_ring_cons__peek(&xdp_socket.rx, 1, &idx_rx);
-		} while (!received);
-	}
 
-	if (!received) return 1;
+          next_pre = next;
+          substract_ns(&next_pre, 120 * 1000);
+
+          ret = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &next_pre, NULL);
+          if (ret) {
+            fprintf(stderr, "clock_nanosleep returned error: %d, aborting...\n", ret);
+            exit(EXIT_FAILURE);
+          }
+
+          do {
+            received = xsk_ring_cons__peek(&xdp_socket.rx, 1, &idx_rx);
+          } while(!received);
+	}
 
 	if (received != 1)
-		error(EXIT_FAILURE, errno,
-		      "Received more packets than expected");
+		error(EXIT_FAILURE, errno, "Received %d packets", received);
+
+         /* Get the packet */
+        addr = xsk_ring_cons__rx_desc(&xdp_socket.rx, idx_rx)->addr;
+        len  = xsk_ring_cons__rx_desc(&xdp_socket.rx, idx_rx)->len;
+
+        /* Parse it */
+        parse_raw_packet(xsk_umem__add_offset_to_addr(addr), len);
+
 	return 0;
 }
 void recv_xdp_cleanup(void) {
@@ -368,10 +427,10 @@ void close_xdp_socket(void) {
 }
 
 #else
-void init_xdp_recv(ingress_param_t * _params) { (void) _params; }
+void init_xdp_recv(ingress_param_t * _params, ingress_stat_t *_stats) { (void) _params; (void) _stats; }
 void setup_poll_fd(void) {}
 void close_xdp_socket(void) {}
-int recv_xdp_packet(void) { return 0; }
+int recv_xdp_packet(struct timespec next) { (void) next; return 0; }
 void recv_xdp_cleanup(void) {}
 #endif
 

packet-exchange/src/recv_packet.h

@@ -29,6 +29,7 @@ typedef struct ingress_stat {
 	uint64_t high_jitter;
 
 	char data[MAX_BUFFER_SIZE];
+	char * xdp_data;
 } ingress_stat_t;
 
 void init_udp_recv(ingress_param_t *_params, ingress_stat_t *stats,
@@ -55,8 +56,8 @@ struct xdpsock {
 };
 #endif
 
-void init_xdp_recv(ingress_param_t * _params);
-int recv_xdp_packet(void);
+void init_xdp_recv(ingress_param_t * _params, ingress_stat_t *_stats);
+int recv_xdp_packet(struct timespec next);
 void recv_xdp_cleanup(void);
 void setup_poll_fd(void);
 void close_xdp_socket(void);

packet-exchange/src/xdp_kern.c

@@ -9,6 +9,10 @@
 #include <linux/udp.h>
 
 #include "bpf_helpers.h"
+#include "bpf_endian.h"
+#include "parsing_helpers.h"
+
+#define UDP_PORT 50000
 
 #define bpf_printk(fmt, ...)                                               \
 	({                                                                 \
@@ -17,44 +21,51 @@
 	})
 
 struct bpf_map_def SEC("maps") xsks_map = {
-    .type = BPF_MAP_TYPE_XSKMAP,
-    .key_size = sizeof(int),
-    .value_size = sizeof(int),
-    .max_entries = 64,
+	.type = BPF_MAP_TYPE_XSKMAP,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = 64,
 };
 
-static inline int parse_ipv4(void *data, unsigned long long nh_off,
-			     void *data_end) {
-	struct iphdr *iph = data + nh_off;
-
-	if ((void *)(iph + 1) > data_end) return 0;
-
-	return iph->protocol;
-}
-
 SEC("xdp_sock")
-int xdp_sock_prog(struct xdp_md *ctx) {
+int xdp_sock_prog(struct xdp_md *ctx)
+{
+	int eth_type, ip_type, index;
+	struct ethhdr *eth;
+	struct iphdr *iphdr;
+	struct ipv6hdr *ipv6hdr;
 	void *data_end = (void *)(long)ctx->data_end;
 	void *data = (void *)(long)ctx->data;
-	struct ethhdr *eth = data;
-	int idx = ctx->rx_queue_index;
-	unsigned int ipproto = 0;
-	unsigned long long nh_off;
+	struct hdr_cursor nh = { .pos = data };
+
+        index = ctx->rx_queue_index;
+
+	eth_type = parse_ethhdr(&nh, data_end, &eth);
+	if (eth_type < 0)
+		return XDP_PASS;
 
-	/* Check if it's a UDP frame: If UDP -> Redirect to active xsk for user
-	 * space. If not -> pass to stack.
-	 */
-	nh_off = sizeof(*eth);
-	if (data + nh_off > data_end) return XDP_PASS;
+	if (eth_type == bpf_htons(ETH_P_IP)) {
+		ip_type = parse_iphdr(&nh, data_end, &iphdr);
+	} else if (eth_type == bpf_htons(ETH_P_IPV6)) {
+		ip_type = parse_ip6hdr(&nh, data_end, &ipv6hdr);
+	} else {
+		return XDP_PASS;
+	}
 
-	if (eth->h_proto == __builtin_bswap16(ETH_P_IP))
-		ipproto = parse_ipv4(data, nh_off, data_end);
+	// only support UDP for now
+	if (ip_type != IPPROTO_UDP)
+		return XDP_PASS;
 
-	if (ipproto != IPPROTO_UDP) return XDP_PASS;
+	struct udphdr *udphdr;
+	// don't mess with ports outside our purview, if specified
+	if (parse_udphdr(&nh, data_end, &udphdr) < 0)
+		return XDP_PASS;
+	if (bpf_ntohs(udphdr->dest) != UDP_PORT)
+		return XDP_PASS;
 
 	/* If socket bound to rx_queue then redirect to user space */
-	if (bpf_map_lookup_elem(&xsks_map, &idx))
-		return bpf_redirect_map(&xsks_map, idx, 0);
+	if (bpf_map_lookup_elem(&xsks_map, &index))
+		return bpf_redirect_map(&xsks_map, index, 0);
 
 	/* Else pass to Linux' network stack */
 	return XDP_PASS;

scripts/exec-ssh-nohup

@@ -7,7 +7,7 @@ send -- "sudo echo\r"
 expect "assword"
 send -- "olimex\r"
 expect "oli@"
-send -- "sudo nohup [lindex $argv 1] > /dev/null > /dev/null &\r"
+send -- "sudo nohup [lindex $argv 1] > /dev/null > [lindex $argv 2] &\r"
 expect "stdout\r"
 send -- \x03
 expect "oli@"

scripts/packet-histogram-start

@@ -97,8 +97,8 @@ stop_opt_filename=${stop_opt_name}${stop_opt_index}
 # Client histogram
 if [ -n "$client_histogram" ]; then
 
-  $script_dir/exec-ssh-nohup $server_board "run-server";
-  $script_dir/exec-ssh-nohup $client_board "run-client -p -i $interval -t -g $server_board";
+  $script_dir/exec-ssh-nohup $server_board "run-server" server_log;
+  $script_dir/exec-ssh-nohup $client_board "run-client -p -i $interval -t -g $server_board" client_log;
 
   echo "$stop_opts -c client_i${interval}_pfast -i $interval $client_board $server_board" > $script_dir/${stop_opt_filename};
 
@@ -107,16 +107,16 @@ elif [ -n "$server_histogram" ]; then
   # Server pfifo_fast qdisc histogram
   if [ -n "$server_pfifo" ]; then
 
-    $script_dir/exec-ssh-nohup $server_board "run-server -g ${interval}$server_opts";
-    $script_dir/exec-ssh-nohup $client_board "run-client -p -i $interval $server_board";
+    $script_dir/exec-ssh-nohup $server_board "run-server -g ${interval}$server_opts" server_log;
+    $script_dir/exec-ssh-nohup $client_board "run-client -p -i $interval $server_board" client_log;
 
     echo "$stop_opts -s server_i${interval} $server_opts -p $client_board $server_board" > $script_dir/${stop_opt_filename};
 
   # Server ETF qdisc histogram
   elif [ -n "$server_etf" ]; then
 
-    $script_dir/exec-ssh-nohup $server_board "run-server -g ${interval}$server_opts";
-    $script_dir/exec-ssh-nohup $client_board "run-client -e $etf_delta -o $etf_offset -i $interval $server_board";
+    $script_dir/exec-ssh-nohup $server_board "run-server -g ${interval}$server_opts" server_log;
+    $script_dir/exec-ssh-nohup $client_board "run-client -e $etf_delta -o $etf_offset -i $interval $server_board" client_log;
 
     echo "$stop_opts -s server_i${interval} $server_opts -e $etf_delta -o $etf_offset $client_board $server_board" > $script_dir/${stop_opt_filename};
 
@@ -127,7 +127,7 @@ elif [ -n "$server_histogram" ]; then
 # cyclictest histogram
 elif [ -n "$cyclictest_histogram" ]; then
 
-  $script_dir/exec-ssh-nohup $board "run-cyclictest -g $cyclictest_opts -i $interval";
+  $script_dir/exec-ssh-nohup $board "run-cyclictest -g $cyclictest_opts -i $interval" cyclictest_log;
 
   echo "$stop_opts -C cyclictest_hist $cyclictest_opts $board" > $script_dir/${stop_opt_filename};
 

scripts/run-client

@@ -6,14 +6,13 @@ usage() {
   cat << ENDUSAGE
 Usage: $0 [-h] QDISC_OPT [CLIENT_OPTS] BOARD_HOSTNAME
    -h              Show help
-   QDISC_OPTS: (-e DELTA [-o USEC] -H | -p) [-q]
+   QDISC_OPTS: [-e DELTA [-o USEC] -H] [-q]
          Which qdisc to use (will call create-qdisc script)
          -e DELTA       Use ETF (Earlier Txtime First) qdisc with specified delta
                         (check tc-etf man page for more information)
          -o USEC        Offset in userspace program to set the timestamp passed to ETF qdisc
          -H             Use hardware offloading for the ETF qdisc (not all hardware supports this)
-         -p             Use pfifo_fast qdisc (default one)
-         -q             Don't setup qdiscs with create-qdisc script
+         -q             Setup qdiscs with create-qdisc script
    CLIENT_OPTS:    -bgt (-c DELAY -s NS | -d TX_BUF_LEN) -i INTERVAL -I if -a CPU [TRACE_OPTS]
          Options passed to the C client program (everything here is optional)
          -b             Measure round trip time 
@@ -46,19 +45,22 @@ ENDUSAGE
 }
 
 # Default interval
-interval=100000
+interval=1000
 
 # Default options
 interface="eth0"
 cpu="1"
-client_options="-p 98"
+client_options="-p 95"
 qdisc_options=""
 etf_offset=500
 tracecmd_events="-e irq -e sched -e net_dev_start_xmit -e net_dev_xmit -e net_dev_xmit_timeout"
 tracecmd_opts=""
 
-while getopts "a:bc:d:e:o:ghi:pqs:tB:E:I:HP:TS:" opt; do
+while getopts "a:bc:d:e:o:ghi:qs:tB:E:I:HP:TS:" opt; do
   case "${opt}" in
+    h )
+        usage
+        ;;
     a )
         cpu=${OPTARG}
         ;;
@@ -74,7 +76,6 @@ while getopts "a:bc:d:e:o:ghi:pqs:tB:E:I:HP:TS:" opt; do
     e )
         use_etf=1
         delta=$((${OPTARG}*1000))
-        qdisc_options+="-e $delta"
         ;;
     o )
         etf_offset=${OPTARG}
@@ -83,20 +84,14 @@ while getopts "a:bc:d:e:o:ghi:pqs:tB:E:I:HP:TS:" opt; do
         client_options+=" -g"
         use_histogram=1
         ;;
-    h )
-        usage
-        exit 1
-        ;;
     i )
         interval=${OPTARG}
         ;;
     p )
         use_pfast=1
-        client_options+=" -q 1"
-        qdisc_options+="-p"
       ;;
     q )
-        dont_create_qdisc=1
+        create_qdisc=1
       ;;
     s )
         client_options+=" -s ${OPTARG}"
@@ -133,27 +128,16 @@ while getopts "a:bc:d:e:o:ghi:pqs:tB:E:I:HP:TS:" opt; do
       ;;
   esac
 done
-
-
 shift $((OPTIND-1))
-
 if [ -z "$1" ]; then
   usage
 fi
 
 qdisc_options+=" -I $interface"
 client_options+=" -a $cpu"
-
 board_name=$1
 board_ip=$(cat /etc/hosts | grep $board_name | awk '{print $1}')
 
-if [ -z "${use_etf}" ] && [ -z "${use_pfast}" ]; then
-  usage
-fi
-if [ -n "${use_etf}" ] && [ -n "${use_pfast}" ]; then
-  usage
-fi
-
 if [ -z "${use_histogram}" ]; then
   client_options+=" -v"
 else
@@ -170,11 +154,15 @@ fi
 
 if [ -n "${use_etf}" ]; then
   client_options+=" -e $etf_offset -q 8"
+  qdisc_options+="-e $delta"
+else
+  client_options+=" -q 1"
+  qdisc_options+="-p"
 fi
 
 client_options+=" -i $interval"
 
-if [ -z "$dont_create_qdisc" ]; then
+if [ -n "$create_qdisc" ]; then
   echo "create-qdisc $qdisc_options";
   $script_dir/create-qdisc $qdisc_options;
 fi
@@ -185,13 +173,19 @@ make client;
 cd $script_dir;
 
 if [ -n "${use_histogram}" ]; then
+
   echo "client $client_options $interface $board_ip > $output;mv $output ~/";
   $script_dir/../packet-exchange/build/client $client_options $interface $board_ip > $output;
   mv $output ~/;
+
 elif [ -n "${use_tracer}" ]; then
+
   echo "trace-cmd record $tracecmd_opts $tracecmd_events ./client $client_options $interface $board_ip";
   trace-cmd record $tracecmd_opts $tracecmd_events $script_dir/../packet-exchange/build/client $client_options $interface $board_ip;
+
 else
+
   echo "client $client_options $interface $board_ip";
   $script_dir/../packet-exchange/build/client $client_options $interface $board_ip;
+
 fi

scripts/run-server

@@ -13,14 +13,18 @@ Usage: $0 [-h] [-I if] [SERVER] | TCPDUMP [TRACE_OPTS]
    SERVER: -bct ((-x | -X) POLL) -g INTERVAL -a CPU
          Options passed to the C server program (everything here is optional)
          -b             Send back packets for round trip measurements
-         -c             Emit a signal on GPIO at the timestamp given in packet
+         -c USEC        Emit a signal on GPIO at the timestamp given in packet, specify interval
                         (to be used with -c option in client program)
-         -C             Measure difference between current time and timestamp sent in tx data
+         -O USEC        Do polling to wakeup signal thread with specified margin
+         -C USEC        Measure difference between current time and timestamp sent in tx data
          -t             Use SO_TIMESTAMPS to see how much time packet spent in kernel
          -x POLL        Use XDP sockets, with a global libbpf installation
          -X POLL        Use XDP sockets, with libbpf located in \$HOME/libbpf folder
             POLL: Polling mode used in server program, 0 to poll with poll function,
                   1 to do active polling
+         -s NS          Specify a CLOCK_REALTIME timestamp at which client should start
+                        (to be used with PTP) (interval needs to be specified with -j)
+         -j USEC        Specify interval (used with -s)
          -g USEC        Generate histograms for measures with the specified interval
          -a CPU         CPU on which to pin the program
    TCPDUMP: -d NB_PACKETS [-i INTERVAL]
@@ -48,7 +52,7 @@ ENDUSAGE
 
 # Default options
 interface="eth0"
-server_options="-p 98"
+server_options="-p 95"
 make_opts=""
 ip="10.100.21."
 tcpdump_interval=1000000
@@ -56,8 +60,14 @@ tracecmd_events="-e irq -e sched -e net -e napi"
 tracecmd_opts=""
 cpu=1
 
-while getopts "a:b:cChtx:X:d:i:g:I:T:E:P:B:MSQ" opt; do
+while getopts "j:a:b:c:C:htx:X:s:d:i:g:I:T:E:P:B:MSQO:" opt; do
   case "${opt}" in
+    h )
+        usage
+        ;;
+    j )
+        server_options+=" -i ${OPTARG}"
+        ;;
     a )
         cpu=${OPTARG}
         ;;
@@ -66,10 +76,13 @@ while getopts "a:b:cChtx:X:d:i:g:I:T:E:P:B:MSQ" opt; do
         board_name=${OPTARG}
         ;;
     c )
-        server_options+=" -c"
+        server_options+=" -c -i ${OPTARG}"
         ;;
+    O )
+        server_options+=" -P ${OPTARG} "
+      ;;
     C )
-        server_options+=" -C"
+        server_options+=" -C -i ${OPTARG}"
         ;;
     d )
         use_tcpdump=1
@@ -83,10 +96,6 @@ while getopts "a:b:cChtx:X:d:i:g:I:T:E:P:B:MSQ" opt; do
         server_options+=" -g -i $interval"
         use_histogram=1
         ;;
-    h )
-        usage
-        exit 1
-        ;;
     t )
         server_options+=" -t"
         ;;
@@ -101,6 +110,9 @@ while getopts "a:b:cChtx:X:d:i:g:I:T:E:P:B:MSQ" opt; do
         server_options+=" -x ${OPTARG}"
 	make_opts=" -e WITH_GIT_XDP=1"
         ;;
+    s )
+        server_options+=" -s ${OPTARG}"
+      ;;
     B )
         tracecmd_opts+=" -m ${OPTARG} -b ${OPTARG}"
       ;;

scripts/run-software-pps

@@ -9,6 +9,7 @@ Usage: $0 [-h] [-i USEC -g -s -t MSEC] BOARD1_HOSTNAME BOARD2_HOSTNAME
    -i USEC        Signal period
    -g             Use GPIO instead of serial
    -t MSEC        Set the start timestamp offset
+   -P USEC        Do polling to wakeup with specified margin
    BOARD_HOSTNAME Uses /etc/hosts to find the IP address associated to the hostname
 ENDUSAGE
 1>&2;
@@ -20,7 +21,7 @@ interval=1000
 pp_opts=""
 ts_offset=6000
 
-while getopts "hi:gt:" opt; do
+while getopts "hi:gt:P:" opt; do
   case "$opt" in
     h)
       usage
@@ -34,6 +35,9 @@ while getopts "hi:gt:" opt; do
     t )
       ts_offset=${OPTARG}
       ;;
+    P )
+      pps_opts+=" -P ${OPTARG} "
+      ;;
     *)
       usage
       ;;
@@ -54,7 +58,9 @@ ts=$($script_dir/get-ptp-time -m $ts_offset)
 echo "Timestamp: $ts";
 
 ssh $board1 "cd tsn-measures/software-pps/build;make";
-$script_dir/exec-ssh-nohup $board1 "tsn-measures/software-pps/build/software-pps -a1 -p97 -i $interval $pps_opts -s $ts";
+echo "$script_dir/exec-ssh-nohup $board1 \"tsn-measures/software-pps/build/software-pps -a1 -p97 -i $interval $pps_opts -s $ts\"" server_log;
+$script_dir/exec-ssh-nohup $board1 "tsn-measures/software-pps/build/software-pps -a1 -p97 -i $interval $pps_opts -s $ts" server_log;
 
 ssh $board2 "cd tsn-measures/software-pps/build;make";
-$script_dir/exec-ssh-nohup $board2 "tsn-measures/software-pps/build/software-pps -a1 -p97 -i $interval $pps_opts -s $ts";
+echo "$script_dir/exec-ssh-nohup $board2 \"tsn-measures/software-pps/build/software-pps -a1 -p97 -i $interval $pps_opts -s $ts\"" server_log;
+$script_dir/exec-ssh-nohup $board2 "tsn-measures/software-pps/build/software-pps -a1 -p97 -i $interval $pps_opts -s $ts" server_log;

scripts/test-board-synchro

@@ -9,6 +9,8 @@ Usage: $0 [-h] [-i USEC -c USEC -t MSEC] [-T] BOARD1_HOSTNAME BOARD2_HOSTNAME
    -i USEC        Specify which interval to use in client
    -c USEC        Specify which offset to use for the timestamp in the packet
    -t MSEC        Set the start timestamp offset
+   -P USEC        Do polling to wakeup signal thread with specified margin
+   -X POLL_MODE   Use XDP with specified poll mode
    -T             Enable tracing on the boards
    BOARD_HOSTNAME Uses /etc/hosts to find the IP address associated to the hostname
 ENDUSAGE
@@ -21,7 +23,7 @@ interval=1000
 server_opts=""
 ts_offset=2000
 
-while getopts "hc:i:o:rt:T" opt; do
+while getopts "hc:i:o:rt:TP:X:" opt; do
   case "${opt}" in
     h )
         usage
@@ -38,6 +40,12 @@ while getopts "hc:i:o:rt:T" opt; do
     T )
         enable_tracing=1
         ;;
+    P )
+        server_opts+=" -P ${OPTARG} "
+      ;;
+    X )
+        server_opts+=" -X ${OPTARG} "
+      ;;
     * )
         usage
         ;;
@@ -62,8 +70,8 @@ $script_dir/sudossh $board2 "killall server";
 killall client;
 killall run-client;
 
-$script_dir/exec-ssh-nohup $board1 "run-server -c $server_opts";
-$script_dir/exec-ssh-nohup $board2 "run-server -c $server_opts";
+$script_dir/exec-ssh-nohup $board1 "run-server -c $interval $server_opts" server_log;
+$script_dir/exec-ssh-nohup $board2 "run-server -c $interval $server_opts" server_log;
 
 ts=$($script_dir/get-ptp-time -m $ts_offset)
 
@@ -76,8 +84,8 @@ if [ -z "$delay" ]; then
   delay=$((interval / 2))
 fi
 
-echo "$script_dir/run-client -a 1 -q -i $interval -p -I enp1s0 -c $delay -s $ts $board1 &> client_enp1s0_log&";
-echo "$script_dir/run-client -a 2 -q -i $interval -p -I enp2s0 -c $delay -s $ts $board2 &> client_enp2s0_log&";
+echo "$script_dir/run-client -a 1 -i $interval -I enp1s0 -c $delay -s $ts $board1 &> client_enp1s0_log&";
+echo "$script_dir/run-client -a 2 -i $interval -I enp2s0 -c $delay -s $ts $board2 &> client_enp2s0_log&";
 
-$script_dir/run-client -a 1 -q -i $interval -p -I enp1s0 -c $delay -s $ts $board1 &> client_enp1s0_log&
-$script_dir/run-client -a 2 -q -i $interval -p -I enp2s0 -c $delay -s $ts $board2 &> client_enp2s0_log&
+$script_dir/run-client -a 1 -i $interval -I enp1s0 -c $delay -s $ts $board1 &> client_enp1s0_log&
+$script_dir/run-client -a 2 -i $interval -I enp2s0 -c $delay -s $ts $board2 &> client_enp2s0_log&

software-pps/src/common.c

@@ -28,6 +28,15 @@ void add_ns(struct timespec *t, uint64_t ns) {
   }
 }
 
+void substract_ns(struct timespec *t, uint64_t ns) {
+  t->tv_nsec -= ns;
+
+  while (t->tv_nsec < 0) {
+    t->tv_sec -= 1;
+    t->tv_nsec += NSEC_PER_SEC;
+  }
+}
+
 uint64_t calcdiff_ns(struct timespec t1, struct timespec t2) {
   uint64_t diff;
   diff = NSEC_PER_SEC * (uint64_t)((int)t1.tv_sec - (int)t2.tv_sec);
@@ -35,6 +44,13 @@ uint64_t calcdiff_ns(struct timespec t1, struct timespec t2) {
   return diff;
 }
 
+int64_t calcdiff_ns_signed(struct timespec t1, struct timespec t2) {
+  int64_t diff;
+  diff = NSEC_PER_SEC * ((int)t1.tv_sec - (int)t2.tv_sec);
+  diff += ((int)t1.tv_nsec - (int)t2.tv_nsec);
+  return diff;
+}
+
 int _max_(int a, int b) { return a > b ? a : b; }
 int _min_(int a, int b) { return a < b ? a : b; }
 

software-pps/src/common.h

@@ -41,7 +41,9 @@
 uint64_t ts_to_uint(struct timespec t);
 struct timespec uint_to_ts(uint64_t t);
 void add_ns(struct timespec *t, uint64_t ns);
+void substract_ns(struct timespec *t, uint64_t ns);
 uint64_t calcdiff_ns(struct timespec t1, struct timespec t2);
+int64_t calcdiff_ns_signed(struct timespec t1, struct timespec t2);
 
 void init_signals(void (*_sighand)(int));
 

software-pps/src/software-pps.c

@@ -20,9 +20,9 @@
 #include <time.h>
 #include <unistd.h>
 
-#include "pulse.h"
-#include "gpio.h"
 #include "common.h"
+#include "gpio.h"
+#include "pulse.h"
 
 // Structs
 
@@ -31,6 +31,8 @@ typedef struct thread_param {
   unsigned int max_cycles;
   int priority;
   int affinity_cpu;
+  int poll;
+  int poll_margin;
   uint64_t start_ts;
 
 } thread_param_t;
@@ -62,11 +64,30 @@ static void help(char *argv[]) {
       "       -l N_CYCLES        RT thread cycles amount (default: infinite)\n"
       "       -s NS              Common start time reference\n"
       "       -g                 Use GPIO instead of serial\n"
+      "       -P USEC            Do polling to wakeup with specified margin\n"
       "       -v                 Verbose\n"
       "\n",
       argv[0]);
 }
 
+static void poll_wakeup(struct timespec ts, int margin) {
+  int ret;
+  struct timespec ts_prev, current;
+
+  ts_prev = ts;
+  substract_ns(&ts_prev, margin * 1000);
+
+  ret = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts_prev, NULL);
+  if (ret) {
+    fprintf(stderr, "clock_nanosleep returned error: %d, aborting...\n", ret);
+    exit(EXIT_FAILURE);
+  }
+
+  do {
+    clock_gettime(CLOCK_REALTIME, &current);
+  } while(calcdiff_ns_signed(ts, current) > 1000);
+}
+
 /*
  * Real-time thread:
  */
@@ -88,11 +109,11 @@ static void *pps_thread(void *p) {
   clock_gettime(CLOCK_REALTIME, &next);
 
   if (thread_params.start_ts) {
-    if(thread_params.start_ts < ts_to_uint(next)) {
+    if (thread_params.start_ts < ts_to_uint(next)) {
       fprintf(stderr, "start timestamp is in the past, aborting...\n");
       exit(EXIT_FAILURE);
     }
-    if(thread_params.start_ts > (ts_to_uint(next) + UINT64_C(3600000000000))) {
+    if (thread_params.start_ts > (ts_to_uint(next) + UINT64_C(3600000000000))) {
       fprintf(stderr, "start timestamp is too high, aborting...\n");
       exit(EXIT_FAILURE);
     }
@@ -105,18 +126,22 @@ static void *pps_thread(void *p) {
         nb_cycles >= ((unsigned int)thread_params.max_cycles))
       break;
 
-
-    if(use_gpio)
+    if (use_gpio)
       toggle_gpio();
     else
       send_pulse();
 
     add_ns(&next, thread_params.interval);
 
-    ret = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &next, NULL);
-    if(ret) {
-      fprintf(stderr, "clock_nanosleep returned error: %d, aborting...\n", ret);
-      exit(EXIT_FAILURE);
+    if(thread_params.poll) {
+      poll_wakeup(next, thread_params.poll_margin);
+    }
+    else {
+      ret = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &next, NULL);
+      if (ret) {
+        fprintf(stderr, "clock_nanosleep returned error: %d, aborting...\n", ret);
+        exit(EXIT_FAILURE);
+      }
     }
   }
 
@@ -139,6 +164,8 @@ int main(int argc, char *argv[]) {
   thread_params.priority = 98;
   thread_params.affinity_cpu = -1;
   thread_params.start_ts = 0;
+  thread_params.poll = 0;
+  thread_params.poll_margin = 75;
   main_params.refresh_rate = 50000;
   main_params.verbose = 0;
   use_gpio = 0;
@@ -153,7 +180,7 @@ int main(int argc, char *argv[]) {
   // Process bash options
   process_options(argc, argv);
 
-  if(use_gpio)
+  if (use_gpio)
     enable_gpio(86);
   else
     enable_pulse();
@@ -193,8 +220,8 @@ int main(int argc, char *argv[]) {
     usleep(main_params.refresh_rate);
 
     if (main_params.verbose) {
-        printf("Toggles: %9" PRIu64 "\n", nb_cycles);
-        printf("\033[%dA", 1);
+      printf("Toggles: %9" PRIu64 "\n", nb_cycles);
+      printf("\033[%dA", 1);
     }
 
     if (thread_params.max_cycles)
@@ -204,12 +231,11 @@ int main(int argc, char *argv[]) {
   exit(EXIT_SUCCESS);
 }
 
-
 /* Process bash options
  */
 static void process_options(int argc, char *argv[]) {
   for (;;) {
-    int c = getopt(argc, argv, "a:hgi:l:p:r:s:v");
+    int c = getopt(argc, argv, "a:hgi:l:p:r:s:vP:");
 
     if (c == -1) break;
 
@@ -242,6 +268,10 @@ static void process_options(int argc, char *argv[]) {
       case 'v':
         main_params.verbose = 1;
         break;
+      case 'P':
+        thread_params.poll = 1;
+        thread_params.poll_margin = atoi(optarg);
+        break;
     }
   }
 }

xdp-testing/Makefile

+IFLAGS += -I ${HOME}/libbpf/include
+
+xdp_%.o: xdp_%.c
+	clang $(IFLAGS) -isystem /usr/include/arm-linux-gnueabihf -S -target bpf -D __BPF_TRACING__ -Wall -O2 -emit-llvm -c -g -o xdp_$*.ll $^
+	llc -march=bpf -filetype=obj -o $@ xdp_$*.ll
+
+clean:
+	$(RM) xdp_*.o xdp_*.ll
+
+.PHONY: clean

xdp-testing/xdp_kern.c

+#define KBUILD_MODNAME "blub"
+
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/if_link.h>
+#include <linux/if_xdp.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+
+#include "bpf_helpers.h"
+
+#define bpf_printk(fmt, ...)                                               \
+	({                                                                 \
+		char ____fmt[] = fmt;                                      \
+		bpf_trace_printk(____fmt, sizeof(____fmt), ##__VA_ARGS__); \
+	})
+
+struct bpf_map_def SEC("maps") xsks_map = {
+    .type = BPF_MAP_TYPE_XSKMAP,
+    .key_size = sizeof(int),
+    .value_size = sizeof(int),
+    .max_entries = 64,
+};
+
+static inline int parse_ipv4(void *data, unsigned long long nh_off,
+			     void *data_end) {
+	struct iphdr *iph = data + nh_off;
+
+	if ((void *)(iph + 1) > data_end) return 0;
+
+	return iph->protocol;
+}
+
+SEC("xdp_sock")
+int xdp_sock_prog(struct xdp_md *ctx) {
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data = (void *)(long)ctx->data;
+	struct ethhdr *eth = data;
+	int idx = ctx->rx_queue_index;
+	unsigned int ipproto = 0;
+	unsigned long long nh_off;
+
+	/* Check if it's a UDP frame: If UDP -> Redirect to active xsk for user
+	 * space. If not -> pass to stack.
+	 */
+	nh_off = sizeof(*eth);
+	if (data + nh_off > data_end) return XDP_PASS;
+
+	if (eth->h_proto == __builtin_bswap16(ETH_P_IP))
+		ipproto = parse_ipv4(data, nh_off, data_end);
+
+	if (ipproto != IPPROTO_UDP) return XDP_PASS;
+
+	/* If socket bound to rx_queue then redirect to user space */
+	if (bpf_map_lookup_elem(&xsks_map, &idx))
+		return bpf_redirect_map(&xsks_map, idx, 0);
+
+	/* Else pass to Linux' network stack */
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";
+

xdp-testing/xdp_pass_kern.c

+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("xdp")
+int  xdp_prog_simple(struct xdp_md *ctx)
+{
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";