Defined in 2 files as a macro:

• include/uapi/linux/tcp.h, line 181 (as a macro)
• tools/include/uapi/linux/tcp.h, line 168 (as a macro)

Referenced in 2 files:

• net/ipv4/tcp.c, line 4260
• tools/testing/selftests/net/tcp_ao/lib/repair.c, line 188