/* * Copyright (c) 1982, 1988 Regents of the University of California. * All rights reserved. * * Redistribution is only permitted until one year after the first shipment * of 4.4BSD by the Regents. Otherwise, redistribution and use in source and * binary forms are permitted provided that: (1) source distributions retain * this entire copyright notice and comment, and (2) distributions including * binaries display the following acknowledgement: This product includes * software developed by the University of California, Berkeley and its * contributors'' in the documentation or other materials provided with the * distribution and in all advertising materials mentioning features or use * of this software. 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 AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. * * @(#)in_cksum.c 7.5 (Berkeley) 6/28/90 */ #include "param.h" #include "mbuf.h" /* * Checksum routine for Internet Protocol family headers (CCI 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) { if ((x) > 65535) (x) -= 65535; } #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} #define ADD(n) asm("adwc n (r10),r9") #define MOP asm("adwc $0,r9") #define BOTCH asm("addl2 r7,r9") in_cksum(m, len) register struct mbuf *m; register int len; { register u_short *w; /* On CCI, known to be r10 */ register int sum = 0; /* On CCI, known to be r9 */ register int mlen = 0; #ifndef lint register int ClearCarry = 0; /* On CCI, known to be r7; see BOTCH */ #endif 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. sum was REDUCEd when we found mlen == -1. */ 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 long boundary so we do longword aligned * memory operations. */ if (3 & (int) w) { REDUCE; if ((1 & (int) w) && (mlen > 0)) { sum <<= 8; s_util.c[0] = *(char *)w; w = (u_short *)((char *)w + 1); mlen--; byte_swapped = 1; } if ((2 & (int) w) && (mlen >= 2)) { sum += *w++; mlen -= 2; } } /* * Do as much of the checksum as possible 32 bits at at time. * In fact, this loop is unrolled to make overhead from * branches &c small. */ while ((mlen -= 32) >= 0) { /* * The loop construct clears carry for us * on vaxen, however, on the CCI machine subtracting * a small postive number from a larger one doesn't. * * Doing a bicpsw is very slow (slows down the routine * by a factor of 2); explicitly adding an immediate * 0 to a register is optimized out; so we fake out * the optimizer and add a register whose contents * is always zero. */ BOTCH; ADD(0); ADD(4); ADD(8); ADD(12); ADD(16); ADD(20); ADD(24); ADD(28); MOP; w += 16; } mlen += 32; while ((mlen -= 8) >= 0) { BOTCH; ADD(0); ADD(4); MOP; w += 4; } mlen += 8; if (mlen == 0 && byte_swapped == 0) continue; /* worth 1% maybe ?? */ REDUCE; while ((mlen -= 2) >= 0) { sum += *w++; } if (byte_swapped) { 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) /* * This mbuf has odd number of bytes. * There could be a word split betwen * this mbuf and the next mbuf. * Save the last byte (to prepend to next mbuf). */ 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 is shifted left by 8 bits) */ s_util.c[1] = 0; sum += s_util.s; } REDUCE; return (~sum & 0xffff); }