Defined in 2 files as a macro:

• include/uapi/linux/tcp.h, line 386 (as a macro)
• tools/include/uapi/linux/tcp.h, line 323 (as a macro)

Referenced in 4 files:

• net/ipv4/tcp_ipv4.c, line 1503
• net/ipv6/tcp_ipv6.c, line 655
• tools/testing/selftests/net/nettest.c, line 277
• tools/testing/selftests/net/tcp_ao/lib/sock.c, line 195