selftests/bpf: Extend netkit tests to validate set {head,tail}room

Extend the netkit selftests to specify and validate the {head,tail}room
on the netdevice:

  # ./vmtest.sh -- ./test_progs -t netkit
  [...]
  ./test_progs -t netkit
  [    1.174147] bpf_testmod: loading out-of-tree module taints kernel.
  [    1.174585] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
  [    1.422307] tsc: Refined TSC clocksource calibration: 3407.983 MHz
  [    1.424511] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fc3e5084, max_idle_ns: 440795359833 ns
  [    1.428092] clocksource: Switched to clocksource tsc
  #363     tc_netkit_basic:OK
  #364     tc_netkit_device:OK
  #365     tc_netkit_multi_links:OK
  #366     tc_netkit_multi_opts:OK
  #367     tc_netkit_neigh_links:OK
  #368     tc_netkit_pkt_type:OK
  #369     tc_netkit_scrub:OK
  Summary: 7/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Nikolay Aleksandrov <razor@blackwall.org>

Author: borkmann

tools/testing/selftests/bpf/prog_tests/tc_netkit.c

@@ -14,6 +14,9 @@
 #include "netlink_helpers.h"
 #include "tc_helpers.h"
 
+#define NETKIT_HEADROOM	32
+#define NETKIT_TAILROOM	8
+
 #define MARK		42
 #define PRIO		0xeb9f
 #define ICMP_ECHO	8
@@ -35,7 +38,7 @@ struct iplink_req {
 };
 
 static int create_netkit(int mode, int policy, int peer_policy, int *ifindex,
-			 bool same_netns, int scrub, int peer_scrub)
+			 bool same_netns, int scrub, int peer_scrub, bool room)
 {
 	struct rtnl_handle rth = { .fd = -1 };
 	struct iplink_req req = {};
@@ -63,6 +66,10 @@ static int create_netkit(int mode, int policy, int peer_policy, int *ifindex,
 	addattr32(&req.n, sizeof(req), IFLA_NETKIT_SCRUB, scrub);
 	addattr32(&req.n, sizeof(req), IFLA_NETKIT_PEER_SCRUB, peer_scrub);
 	addattr32(&req.n, sizeof(req), IFLA_NETKIT_MODE, mode);
+	if (room) {
+		addattr16(&req.n, sizeof(req), IFLA_NETKIT_HEADROOM, NETKIT_HEADROOM);
+		addattr16(&req.n, sizeof(req), IFLA_NETKIT_TAILROOM, NETKIT_TAILROOM);
+	}
 	addattr_nest_end(&req.n, data);
 	addattr_nest_end(&req.n, linkinfo);
 
@@ -185,7 +192,7 @@ void serial_test_tc_netkit_basic(void)
 
 	err = create_netkit(NETKIT_L2, NETKIT_PASS, NETKIT_PASS,
 			    &ifindex, false, NETKIT_SCRUB_DEFAULT,
-			    NETKIT_SCRUB_DEFAULT);
+			    NETKIT_SCRUB_DEFAULT, false);
 	if (err)
 		return;
 
@@ -300,7 +307,7 @@ static void serial_test_tc_netkit_multi_links_target(int mode, int target)
 
 	err = create_netkit(mode, NETKIT_PASS, NETKIT_PASS,
 			    &ifindex, false, NETKIT_SCRUB_DEFAULT,
-			    NETKIT_SCRUB_DEFAULT);
+			    NETKIT_SCRUB_DEFAULT, false);
 	if (err)
 		return;
 
@@ -429,7 +436,7 @@ static void serial_test_tc_netkit_multi_opts_target(int mode, int target)
 
 	err = create_netkit(mode, NETKIT_PASS, NETKIT_PASS,
 			    &ifindex, false, NETKIT_SCRUB_DEFAULT,
-			    NETKIT_SCRUB_DEFAULT);
+			    NETKIT_SCRUB_DEFAULT, false);
 	if (err)
 		return;
 
@@ -544,7 +551,7 @@ void serial_test_tc_netkit_device(void)
 
 	err = create_netkit(NETKIT_L3, NETKIT_PASS, NETKIT_PASS,
 			    &ifindex, true, NETKIT_SCRUB_DEFAULT,
-			    NETKIT_SCRUB_DEFAULT);
+			    NETKIT_SCRUB_DEFAULT, false);
 	if (err)
 		return;
 
@@ -656,7 +663,7 @@ static void serial_test_tc_netkit_neigh_links_target(int mode, int target)
 
 	err = create_netkit(mode, NETKIT_PASS, NETKIT_PASS,
 			    &ifindex, false, NETKIT_SCRUB_DEFAULT,
-			    NETKIT_SCRUB_DEFAULT);
+			    NETKIT_SCRUB_DEFAULT, false);
 	if (err)
 		return;
 
@@ -734,7 +741,7 @@ static void serial_test_tc_netkit_pkt_type_mode(int mode)
 
 	err = create_netkit(mode, NETKIT_PASS, NETKIT_PASS,
 			    &ifindex, true, NETKIT_SCRUB_DEFAULT,
-			    NETKIT_SCRUB_DEFAULT);
+			    NETKIT_SCRUB_DEFAULT, false);
 	if (err)
 		return;
 
@@ -799,15 +806,15 @@ void serial_test_tc_netkit_pkt_type(void)
 	serial_test_tc_netkit_pkt_type_mode(NETKIT_L3);
 }
 
-static void serial_test_tc_netkit_scrub_type(int scrub)
+static void serial_test_tc_netkit_scrub_type(int scrub, bool room)
 {
 	LIBBPF_OPTS(bpf_netkit_opts, optl);
 	struct test_tc_link *skel;
 	struct bpf_link *link;
 	int err, ifindex;
 
 	err = create_netkit(NETKIT_L2, NETKIT_PASS, NETKIT_PASS,
-			    &ifindex, false, scrub, scrub);
+			    &ifindex, false, scrub, scrub, room);
 	if (err)
 		return;
 
@@ -842,6 +849,8 @@ static void serial_test_tc_netkit_scrub_type(int scrub)
 	ASSERT_EQ(skel->bss->seen_tc8, true, "seen_tc8");
 	ASSERT_EQ(skel->bss->mark, scrub == NETKIT_SCRUB_NONE ? MARK : 0, "mark");
 	ASSERT_EQ(skel->bss->prio, scrub == NETKIT_SCRUB_NONE ? PRIO : 0, "prio");
+	ASSERT_EQ(skel->bss->headroom, room ? NETKIT_HEADROOM : 0, "headroom");
+	ASSERT_EQ(skel->bss->tailroom, room ? NETKIT_TAILROOM : 0, "tailroom");
 cleanup:
 	test_tc_link__destroy(skel);
 
@@ -852,6 +861,6 @@ static void serial_test_tc_netkit_scrub_type(int scrub)
 
 void serial_test_tc_netkit_scrub(void)
 {
-	serial_test_tc_netkit_scrub_type(NETKIT_SCRUB_DEFAULT);
-	serial_test_tc_netkit_scrub_type(NETKIT_SCRUB_NONE);
+	serial_test_tc_netkit_scrub_type(NETKIT_SCRUB_DEFAULT, false);
+	serial_test_tc_netkit_scrub_type(NETKIT_SCRUB_NONE, true);
 }

tools/testing/selftests/bpf/progs/test_tc_link.c

@@ -8,6 +8,7 @@
 #include <linux/if_packet.h>
 #include <bpf/bpf_endian.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
 
 char LICENSE[] SEC("license") = "GPL";
 
@@ -27,6 +28,7 @@ bool seen_host;
 bool seen_mcast;
 
 int mark, prio;
+unsigned short headroom, tailroom;
 
 SEC("tc/ingress")
 int tc1(struct __sk_buff *skb)
@@ -104,11 +106,24 @@ int tc7(struct __sk_buff *skb)
 	return TCX_PASS;
 }
 
+struct sk_buff {
+	struct net_device *dev;
+};
+
+struct net_device {
+	unsigned short needed_headroom;
+	unsigned short needed_tailroom;
+};
+
 SEC("tc/egress")
 int tc8(struct __sk_buff *skb)
 {
+	struct net_device *dev = BPF_CORE_READ((struct sk_buff *)skb, dev);
+
 	seen_tc8 = true;
 	mark = skb->mark;
 	prio = skb->priority;
+	headroom = BPF_CORE_READ(dev, needed_headroom);
+	tailroom = BPF_CORE_READ(dev, needed_tailroom);
 	return TCX_PASS;
 }