Defined in 2 files as a macro:

• include/uapi/linux/tcp.h, line 324 (as a macro)
• tools/include/uapi/linux/tcp.h, line 323 (as a macro)

Referenced in 3 files:

• net/ipv4/tcp_ipv4.c, line 1243
• net/ipv6/tcp_ipv6.c, line 598
• tools/testing/selftests/net/nettest.c, line 258