diff --git a/tools/testing/selftests/net/af_unix/diag_uid.c b/tools/testing/selftests/net/af_unix/diag_uid.c
index 79a3dd75590e..279d0c5f70d3 100644
--- a/tools/testing/selftests/net/af_unix/diag_uid.c
+++ b/tools/testing/selftests/net/af_unix/diag_uid.c
@@ -1,7 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright Amazon.com Inc. or its affiliates. */
-
-#define _GNU_SOURCE
 #include <sched.h>
 
 #include <unistd.h>
diff --git a/tools/testing/selftests/net/af_unix/scm_pidfd.c b/tools/testing/selftests/net/af_unix/scm_pidfd.c
index 7e534594167e..2986b8cd0418 100644
--- a/tools/testing/selftests/net/af_unix/scm_pidfd.c
+++ b/tools/testing/selftests/net/af_unix/scm_pidfd.c
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0 OR MIT
-#define _GNU_SOURCE
 #include <error.h>
 #include <limits.h>
 #include <stddef.h>
diff --git a/tools/testing/selftests/net/af_unix/scm_rights.c b/tools/testing/selftests/net/af_unix/scm_rights.c
index bab606c9f1eb..146a8d7a8cd9 100644
--- a/tools/testing/selftests/net/af_unix/scm_rights.c
+++ b/tools/testing/selftests/net/af_unix/scm_rights.c
@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright Amazon.com Inc. or its affiliates. */
-#define _GNU_SOURCE
 #include <sched.h>
 
 #include <stdio.h>
diff --git a/tools/testing/selftests/net/af_unix/unix_connect.c b/tools/testing/selftests/net/af_unix/unix_connect.c
index d799fd8f5c7c..34e816862cc7 100644
--- a/tools/testing/selftests/net/af_unix/unix_connect.c
+++ b/tools/testing/selftests/net/af_unix/unix_connect.c
@@ -1,6 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
 #include <sched.h>
 
 #include <stddef.h>
diff --git a/tools/testing/selftests/net/csum.c b/tools/testing/selftests/net/csum.c
index b9f3fc3c3426..28f8241b8567 100644
--- a/tools/testing/selftests/net/csum.c
+++ b/tools/testing/selftests/net/csum.c
@@ -58,9 +58,6 @@
  * different seed for each run (and logs this for reproducibility). It
  * is advised to enable this for extra coverage in continuous testing.
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <asm/byteorder.h>
 #include <errno.h>
diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
index 6038b96ecee8..dd370c88af1e 100644
--- a/tools/testing/selftests/net/gro.c
+++ b/tools/testing/selftests/net/gro.c
@@ -34,9 +34,6 @@
  * flakiness is to be expected.
  *
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/ip_defrag.c b/tools/testing/selftests/net/ip_defrag.c
index f9ed749fd8c7..80c9e567a3d8 100644
--- a/tools/testing/selftests/net/ip_defrag.c
+++ b/tools/testing/selftests/net/ip_defrag.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/ipsec.c b/tools/testing/selftests/net/ipsec.c
index be4a30a0d02a..04aa06d26b09 100644
--- a/tools/testing/selftests/net/ipsec.c
+++ b/tools/testing/selftests/net/ipsec.c
@@ -3,9 +3,6 @@
  * ipsec.c - Check xfrm on veth inside a net-ns.
  * Copyright (c) 2018 Dmitry Safonov
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <asm/types.h>
 #include <errno.h>
diff --git a/tools/testing/selftests/net/ipv6_flowlabel.c b/tools/testing/selftests/net/ipv6_flowlabel.c
index 708a9822259d..b7e0c3c02e20 100644
--- a/tools/testing/selftests/net/ipv6_flowlabel.c
+++ b/tools/testing/selftests/net/ipv6_flowlabel.c
@@ -1,8 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Test IPV6_FLOWINFO cmsg on send and recv */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <asm/byteorder.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/ipv6_flowlabel_mgr.c b/tools/testing/selftests/net/ipv6_flowlabel_mgr.c
index af95b48acea9..ebd219ba386e 100644
--- a/tools/testing/selftests/net/ipv6_flowlabel_mgr.c
+++ b/tools/testing/selftests/net/ipv6_flowlabel_mgr.c
@@ -1,8 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Test IPV6_FLOWINFO_MGR */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <error.h>
 #include <errno.h>
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index d2043ec3bf6d..ea93030ed3ec 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <errno.h>
 #include <limits.h>
 #include <fcntl.h>
diff --git a/tools/testing/selftests/net/mptcp/mptcp_inq.c b/tools/testing/selftests/net/mptcp/mptcp_inq.c
index 218aac467321..c5bf873d76c2 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_inq.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_inq.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
index 926b0be87c99..7203ca9900e9 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
index bdc03a2097e8..9278bf585c80 100644
--- a/tools/testing/selftests/net/msg_zerocopy.c
+++ b/tools/testing/selftests/net/msg_zerocopy.c
@@ -24,9 +24,6 @@
  * 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>
diff --git a/tools/testing/selftests/net/netfilter/audit_logread.c b/tools/testing/selftests/net/netfilter/audit_logread.c
index a0a880fc2d9d..0b3dddab1c52 100644
--- a/tools/testing/selftests/net/netfilter/audit_logread.c
+++ b/tools/testing/selftests/net/netfilter/audit_logread.c
@@ -1,6 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
 #include <errno.h>
 #include <fcntl.h>
 #include <poll.h>
diff --git a/tools/testing/selftests/net/netfilter/conntrack_dump_flush.c b/tools/testing/selftests/net/netfilter/conntrack_dump_flush.c
index bd9317bf5ada..fb6c5d1b6f63 100644
--- a/tools/testing/selftests/net/netfilter/conntrack_dump_flush.c
+++ b/tools/testing/selftests/net/netfilter/conntrack_dump_flush.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <time.h>
 #include <libmnl/libmnl.h>
 #include <netinet/ip.h>
diff --git a/tools/testing/selftests/net/nettest.c b/tools/testing/selftests/net/nettest.c
index cd8a58097448..88e1d3b2ddf1 100644
--- a/tools/testing/selftests/net/nettest.c
+++ b/tools/testing/selftests/net/nettest.c
@@ -3,8 +3,6 @@
  *
  * Copyright (c) 2013-2019 David Ahern <dsahern@gmail.com>. All rights reserved.
  */
-
-#define _GNU_SOURCE
 #include <features.h>
 #include <sys/types.h>
 #include <sys/ioctl.h>
diff --git a/tools/testing/selftests/net/psock_fanout.c b/tools/testing/selftests/net/psock_fanout.c
index 1a736f700be4..5b2d34440ae9 100644
--- a/tools/testing/selftests/net/psock_fanout.c
+++ b/tools/testing/selftests/net/psock_fanout.c
@@ -26,9 +26,6 @@
  * Todo:
  * - functionality: PACKET_FANOUT_FLAG_DEFRAG
  */
-
-#define _GNU_SOURCE		/* for sched_setaffinity */
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/tools/testing/selftests/net/psock_snd.c b/tools/testing/selftests/net/psock_snd.c
index edf1e6f80d41..2f29b513e18f 100644
--- a/tools/testing/selftests/net/psock_snd.c
+++ b/tools/testing/selftests/net/psock_snd.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/reuseport_addr_any.c b/tools/testing/selftests/net/reuseport_addr_any.c
index b8475cb29be7..9ee6ece52865 100644
--- a/tools/testing/selftests/net/reuseport_addr_any.c
+++ b/tools/testing/selftests/net/reuseport_addr_any.c
@@ -3,9 +3,6 @@
 /* Test that sockets listening on a specific address are preferred
  * over sockets listening on addr_any.
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/reuseport_bpf_cpu.c b/tools/testing/selftests/net/reuseport_bpf_cpu.c
index 2d646174729f..e93e38cfb2a8 100644
--- a/tools/testing/selftests/net/reuseport_bpf_cpu.c
+++ b/tools/testing/selftests/net/reuseport_bpf_cpu.c
@@ -11,9 +11,6 @@
  * This entire process is done for several different core id permutations
  * and for each IPv4/IPv6 and TCP/UDP combination.
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/reuseport_bpf_numa.c b/tools/testing/selftests/net/reuseport_bpf_numa.c
index c9ba36aa688e..502fdb9ce770 100644
--- a/tools/testing/selftests/net/reuseport_bpf_numa.c
+++ b/tools/testing/selftests/net/reuseport_bpf_numa.c
@@ -3,9 +3,6 @@
  * Test functionality of BPF filters with SO_REUSEPORT. Same test as
  * in reuseport_bpf_cpu, only as one socket per NUMA node.
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/reuseport_dualstack.c b/tools/testing/selftests/net/reuseport_dualstack.c
index fb7a59ed759e..d3c3d3f39f8f 100644
--- a/tools/testing/selftests/net/reuseport_dualstack.c
+++ b/tools/testing/selftests/net/reuseport_dualstack.c
@@ -10,9 +10,6 @@
  * This test creates these mixed AF_INET/AF_INET6 sockets and asserts the
  * AF_INET preference for v4 packets.
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/so_incoming_cpu.c b/tools/testing/selftests/net/so_incoming_cpu.c
index e9fa14e10732..95bd0cdc3253 100644
--- a/tools/testing/selftests/net/so_incoming_cpu.c
+++ b/tools/testing/selftests/net/so_incoming_cpu.c
@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright Amazon.com Inc. or its affiliates. */
-#define _GNU_SOURCE
 #include <sched.h>
 
 #include <fcntl.h>
diff --git a/tools/testing/selftests/net/so_netns_cookie.c b/tools/testing/selftests/net/so_netns_cookie.c
index b39e87e967cd..18532d564f79 100644
--- a/tools/testing/selftests/net/so_netns_cookie.c
+++ b/tools/testing/selftests/net/so_netns_cookie.c
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-#define _GNU_SOURCE
 #include <sched.h>
 #include <unistd.h>
 #include <stdio.h>
diff --git a/tools/testing/selftests/net/so_txtime.c b/tools/testing/selftests/net/so_txtime.c
index 8457b7ccbc09..011a24af9786 100644
--- a/tools/testing/selftests/net/so_txtime.c
+++ b/tools/testing/selftests/net/so_txtime.c
@@ -9,9 +9,6 @@
  * the expected stream. Sender will read transmit timestamps from the error
  * queue. The streams can differ due to out-of-order delivery and drops.
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <error.h>
 #include <errno.h>
diff --git a/tools/testing/selftests/net/tap.c b/tools/testing/selftests/net/tap.c
index 247c3b3ac1c9..fa78b92d9740 100644
--- a/tools/testing/selftests/net/tap.c
+++ b/tools/testing/selftests/net/tap.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
diff --git a/tools/testing/selftests/net/tcp_fastopen_backup_key.c b/tools/testing/selftests/net/tcp_fastopen_backup_key.c
index c1cb0c75156a..d30f89bb944c 100644
--- a/tools/testing/selftests/net/tcp_fastopen_backup_key.c
+++ b/tools/testing/selftests/net/tcp_fastopen_backup_key.c
@@ -12,7 +12,6 @@
  * there are no cases in which a cookie is not accepted by verifying
  * that TcpExtTCPFastOpenPassiveFail remains 0.
  */
-#define _GNU_SOURCE
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/tcp_inq.c b/tools/testing/selftests/net/tcp_inq.c
index bd6a9c7a3e8a..71ee145f151e 100644
--- a/tools/testing/selftests/net/tcp_inq.c
+++ b/tools/testing/selftests/net/tcp_inq.c
@@ -5,8 +5,6 @@
  *
  * Simple example on how to use TCP_INQ and TCP_CM_INQ.
  */
-#define _GNU_SOURCE
-
 #include <error.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
diff --git a/tools/testing/selftests/net/tcp_mmap.c b/tools/testing/selftests/net/tcp_mmap.c
index 4fcce5150850..72d5f1207ee0 100644
--- a/tools/testing/selftests/net/tcp_mmap.c
+++ b/tools/testing/selftests/net/tcp_mmap.c
@@ -46,7 +46,6 @@
  * received 32768 MB (99.9939 % mmap'ed) in 7.43764 s, 36.9577 Gbit
  *   cpu usage user:0.035 sys:3.467, 106.873 usec per MB, 65530 c-switches
  */
-#define _GNU_SOURCE
 #include <pthread.h>
 #include <sys/types.h>
 #include <fcntl.h>
diff --git a/tools/testing/selftests/net/tls.c b/tools/testing/selftests/net/tls.c
index f27a12d2a2c9..6dbad97d1d0a 100644
--- a/tools/testing/selftests/net/tls.c
+++ b/tools/testing/selftests/net/tls.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/toeplitz.c b/tools/testing/selftests/net/toeplitz.c
index 9ba03164d73a..e2d739892ce4 100644
--- a/tools/testing/selftests/net/toeplitz.c
+++ b/tools/testing/selftests/net/toeplitz.c
@@ -20,9 +20,6 @@
  * 5. Compute the cpu that RPS should select based on rx_hash and $rps_bitmap
  * 6. Compare the cpus from 4 and 5
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/tun.c b/tools/testing/selftests/net/tun.c
index fa83918b62d1..a64dcfb242c1 100644
--- a/tools/testing/selftests/net/tun.c
+++ b/tools/testing/selftests/net/tun.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
diff --git a/tools/testing/selftests/net/txring_overwrite.c b/tools/testing/selftests/net/txring_overwrite.c
index 7d9ea039450a..96972e0110a0 100644
--- a/tools/testing/selftests/net/txring_overwrite.c
+++ b/tools/testing/selftests/net/txring_overwrite.c
@@ -4,9 +4,6 @@
  * 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>
diff --git a/tools/testing/selftests/net/txtimestamp.c b/tools/testing/selftests/net/txtimestamp.c
index ec60a16c9307..33dba9e90dea 100644
--- a/tools/testing/selftests/net/txtimestamp.c
+++ b/tools/testing/selftests/net/txtimestamp.c
@@ -16,9 +16,6 @@
  * This test requires a dummy TCP server.
  * A simple `nc6 [-u] -l -p $DESTPORT` will do
  */
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <asm/types.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/udpgso.c b/tools/testing/selftests/net/udpgso.c
index 85b3baa3f7f3..9dc1026a033a 100644
--- a/tools/testing/selftests/net/udpgso.c
+++ b/tools/testing/selftests/net/udpgso.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <stddef.h>
 #include <arpa/inet.h>
 #include <error.h>
diff --git a/tools/testing/selftests/net/udpgso_bench_rx.c b/tools/testing/selftests/net/udpgso_bench_rx.c
index 1cbadd267c96..999df1236320 100644
--- a/tools/testing/selftests/net/udpgso_bench_rx.c
+++ b/tools/testing/selftests/net/udpgso_bench_rx.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <error.h>
 #include <errno.h>
diff --git a/tools/testing/selftests/net/udpgso_bench_tx.c b/tools/testing/selftests/net/udpgso_bench_tx.c
index 477392715a9a..d7632993b354 100644
--- a/tools/testing/selftests/net/udpgso_bench_tx.c
+++ b/tools/testing/selftests/net/udpgso_bench_tx.c
@@ -1,7 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
-#define _GNU_SOURCE
-
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
