Defined in 2 files as a macro:

• include/uapi/linux/tcp.h, line 325 (as a macro)
• tools/include/uapi/linux/tcp.h, line 324 (as a macro)

Referenced in 3 files:

• net/ipv4/tcp_ipv4.c, line 1250
• net/ipv6/tcp_ipv6.c, line 608
• tools/testing/selftests/net/nettest.c, line 267