diff --git a/sys/netinet/in_cksum.c b/sys/netinet/in_cksum.c
deleted file mode 100644
--- a/sys/netinet/in_cksum.c
+++ /dev/null
@@ -1,148 +0,0 @@
-/*-
- * SPDX-License-Identifier: BSD-3-Clause
- *
- * Copyright (c) 1988, 1992, 1993
- *	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.
- *
- *	@(#)in_cksum.c	8.1 (Berkeley) 6/10/93
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-#include <sys/param.h>
-#include <sys/mbuf.h>
-
-/*
- * Checksum routine for Internet Protocol family headers (Portable Version).
- *
- * This routine is very heavily used in the network
- * code and should be modified for each CPU to be as fast as possible.
- */
-
-#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
-#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
-
-int
-in_cksum(struct mbuf *m, int len)
-{
-	u_short *w;
-	int sum = 0;
-	int mlen = 0;
-	int byte_swapped = 0;
-
-	union {
-		char	c[2];
-		u_short	s;
-	} s_util;
-	union {
-		u_short s[2];
-		long	l;
-	} l_util;
-
-	for (;m && len; m = m->m_next) {
-		if (m->m_len == 0)
-			continue;
-		w = mtod(m, u_short *);
-		if (mlen == -1) {
-			/*
-			 * The first byte of this mbuf is the continuation
-			 * of a word spanning between this mbuf and the
-			 * last mbuf.
-			 *
-			 * s_util.c[0] is already saved when scanning previous
-			 * mbuf.
-			 */
-			s_util.c[1] = *(char *)w;
-			sum += s_util.s;
-			w = (u_short *)((char *)w + 1);
-			mlen = m->m_len - 1;
-			len--;
-		} else
-			mlen = m->m_len;
-		if (len < mlen)
-			mlen = len;
-		len -= mlen;
-		/*
-		 * Force to even boundary.
-		 */
-		if ((1 & (uintptr_t) w) && (mlen > 0)) {
-			REDUCE;
-			sum <<= 8;
-			s_util.c[0] = *(u_char *)w;
-			w = (u_short *)((char *)w + 1);
-			mlen--;
-			byte_swapped = 1;
-		}
-		/*
-		 * Unroll the loop to make overhead from
-		 * branches &c small.
-		 */
-		while ((mlen -= 32) >= 0) {
-			sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
-			sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
-			sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
-			sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
-			w += 16;
-		}
-		mlen += 32;
-		while ((mlen -= 8) >= 0) {
-			sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
-			w += 4;
-		}
-		mlen += 8;
-		if (mlen == 0 && byte_swapped == 0)
-			continue;
-		REDUCE;
-		while ((mlen -= 2) >= 0) {
-			sum += *w++;
-		}
-		if (byte_swapped) {
-			REDUCE;
-			sum <<= 8;
-			byte_swapped = 0;
-			if (mlen == -1) {
-				s_util.c[1] = *(char *)w;
-				sum += s_util.s;
-				mlen = 0;
-			} else
-				mlen = -1;
-		} else if (mlen == -1)
-			s_util.c[0] = *(char *)w;
-	}
-	if (len)
-		printf("cksum: out of data\n");
-	if (mlen == -1) {
-		/* The last mbuf has odd # of bytes. Follow the
-		   standard (the odd byte may be shifted left by 8 bits
-		   or not as determined by endian-ness of the machine) */
-		s_util.c[1] = 0;
-		sum += s_util.s;
-	}
-	REDUCE;
-	return (~sum & 0xffff);
-}