diff --git a/sys/amd64/include/in_cksum.h b/sys/amd64/include/in_cksum.h
index 7407b4ad7104..d9830168f5ab 100644
--- a/sys/amd64/include/in_cksum.h
+++ b/sys/amd64/include/in_cksum.h
@@ -1,53 +1,51 @@
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1990 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	from tahoe:	in_cksum.c	1.2	86/01/05
  *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
  *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
  * $FreeBSD$
  */
 
 #ifndef _MACHINE_IN_CKSUM_H_
 #define	_MACHINE_IN_CKSUM_H_	1
 
-#include <sys/cdefs.h>
-
 #define in_cksum(m, len)	in_cksum_skip(m, len, 0)
 
 #ifdef _KERNEL
 #if defined(IPVERSION) && (IPVERSION == 4)
 u_int in_cksum_hdr(const struct ip *ip);
 #endif
 u_short	in_addword(u_short sum, u_short b);
 u_short	in_pseudo(u_int sum, u_int b, u_int c);
 u_short	in_cksum_skip(struct mbuf *m, int len, int skip);
 #endif
 
 #endif /* _MACHINE_IN_CKSUM_H_ */
diff --git a/sys/arm/include/in_cksum.h b/sys/arm/include/in_cksum.h
index 352d46f07e7b..343052f4556c 100644
--- a/sys/arm/include/in_cksum.h
+++ b/sys/arm/include/in_cksum.h
@@ -1,69 +1,67 @@
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1990 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	from tahoe:	in_cksum.c	1.2	86/01/05
  *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
  *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
  * $FreeBSD$
  */
 
 #ifndef _MACHINE_IN_CKSUM_H_
 #define	_MACHINE_IN_CKSUM_H_	1
 
-#include <sys/cdefs.h>
-
 #ifdef _KERNEL
 
 #define	HAVE_MD_IN_CKSUM
 
 u_short in_cksum(struct mbuf *m, int len);
 u_short in_addword(u_short sum, u_short b);
 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
 u_int do_cksum(const void *, int);
 #if defined(IPVERSION) && (IPVERSION == 4)
 u_int in_cksum_hdr(const struct ip *);
 #endif
 
 static __inline u_short
 in_pseudo(u_int sum, u_int b, u_int c)
 {
 	__asm __volatile("adds %0, %0, %1\n"
 	    		"adcs %0, %0, %2\n"
 			"adc %0, %0, #0\n"
 			: "+r" (sum)
 			: "r" (b), "r" (c));
 	sum = (sum & 0xffff) + (sum >> 16);
 	if (sum > 0xffff)
 		sum -= 0xffff;
 	return (sum);
 }
 
 #endif /* _KERNEL */
 #endif /* _MACHINE_IN_CKSUM_H_ */
diff --git a/sys/arm64/include/in_cksum.h b/sys/arm64/include/in_cksum.h
index 522ba005a0e4..add7569a9f4a 100644
--- a/sys/arm64/include/in_cksum.h
+++ b/sys/arm64/include/in_cksum.h
@@ -1,52 +1,50 @@
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	from tahoe:	in_cksum.c	1.2	86/01/05
  *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
  *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
  * $FreeBSD$
  */
 
 #ifndef _MACHINE_IN_CKSUM_H_
 #define	_MACHINE_IN_CKSUM_H_	1
 
-#include <sys/cdefs.h>
-
 #ifdef _KERNEL
 #define	in_cksum(m, len)	in_cksum_skip(m, len, 0)
 u_short in_addword(u_short sum, u_short b);
 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
 u_int do_cksum(const void *, int);
 #if defined(IPVERSION) && (IPVERSION == 4)
 u_int in_cksum_hdr(const struct ip *);
 #endif
 
 u_short in_pseudo(u_int sum, u_int b, u_int c);
 
 #endif /* _KERNEL */
 #endif /* _MACHINE_IN_CKSUM_H_ */
diff --git a/sys/powerpc/include/in_cksum.h b/sys/powerpc/include/in_cksum.h
index 7407b4ad7104..d9830168f5ab 100644
--- a/sys/powerpc/include/in_cksum.h
+++ b/sys/powerpc/include/in_cksum.h
@@ -1,53 +1,51 @@
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1990 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	from tahoe:	in_cksum.c	1.2	86/01/05
  *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
  *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
  * $FreeBSD$
  */
 
 #ifndef _MACHINE_IN_CKSUM_H_
 #define	_MACHINE_IN_CKSUM_H_	1
 
-#include <sys/cdefs.h>
-
 #define in_cksum(m, len)	in_cksum_skip(m, len, 0)
 
 #ifdef _KERNEL
 #if defined(IPVERSION) && (IPVERSION == 4)
 u_int in_cksum_hdr(const struct ip *ip);
 #endif
 u_short	in_addword(u_short sum, u_short b);
 u_short	in_pseudo(u_int sum, u_int b, u_int c);
 u_short	in_cksum_skip(struct mbuf *m, int len, int skip);
 #endif
 
 #endif /* _MACHINE_IN_CKSUM_H_ */
diff --git a/sys/riscv/include/in_cksum.h b/sys/riscv/include/in_cksum.h
index 522ba005a0e4..add7569a9f4a 100644
--- a/sys/riscv/include/in_cksum.h
+++ b/sys/riscv/include/in_cksum.h
@@ -1,52 +1,50 @@
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	from tahoe:	in_cksum.c	1.2	86/01/05
  *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
  *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
  * $FreeBSD$
  */
 
 #ifndef _MACHINE_IN_CKSUM_H_
 #define	_MACHINE_IN_CKSUM_H_	1
 
-#include <sys/cdefs.h>
-
 #ifdef _KERNEL
 #define	in_cksum(m, len)	in_cksum_skip(m, len, 0)
 u_short in_addword(u_short sum, u_short b);
 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
 u_int do_cksum(const void *, int);
 #if defined(IPVERSION) && (IPVERSION == 4)
 u_int in_cksum_hdr(const struct ip *);
 #endif
 
 u_short in_pseudo(u_int sum, u_int b, u_int c);
 
 #endif /* _KERNEL */
 #endif /* _MACHINE_IN_CKSUM_H_ */