diff options
Diffstat (limited to 'slirp/cksum.c')
| -rw-r--r-- | slirp/cksum.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/slirp/cksum.c b/slirp/cksum.c new file mode 100644 index 0000000..f8f7512 --- /dev/null +++ b/slirp/cksum.c @@ -0,0 +1,141 @@ +/* + * 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. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. 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 + * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp + */ + +#include <slirp.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. + * + * XXX Since we will never span more than 1 mbuf, we can optimise this + */ + +#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 cksum(struct mbuf *m, int len) +{ + register u_int16_t *w; + register int sum = 0; + register int mlen = 0; + int byte_swapped = 0; + + union { + u_int8_t c[2]; + u_int16_t s; + } s_util; + union { + u_int16_t s[2]; + u_int32_t l; + } l_util; + + if (m->m_len == 0) + goto cont; + w = mtod(m, u_int16_t *); + + mlen = m->m_len; + + if (len < mlen) + mlen = len; + len -= mlen; + /* + * Force to even boundary. + */ + if ((1 & (long) w) && (mlen > 0)) { + REDUCE; + sum <<= 8; + s_util.c[0] = *(u_int8_t *)w; + w = (u_int16_t *)((int8_t *)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) + goto cont; + REDUCE; + while ((mlen -= 2) >= 0) { + sum += *w++; + } + + if (byte_swapped) { + REDUCE; + sum <<= 8; + byte_swapped = 0; + if (mlen == -1) { + s_util.c[1] = *(u_int8_t *)w; + sum += s_util.s; + mlen = 0; + } else + + mlen = -1; + } else if (mlen == -1) + s_util.c[0] = *(u_int8_t *)w; + +cont: +#ifdef DEBUG + if (len) { + DEBUG_ERROR((dfd, "cksum: out of data\n")); + DEBUG_ERROR((dfd, " len = %d\n", len)); + } +#endif + 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); +} |
