1*33840Skarels /* 2*33840Skarels * Copyright (c) 1988 Regents of the University of California. 3*33840Skarels * All rights reserved. 4*33840Skarels * 5*33840Skarels * Redistribution and use in source and binary forms are permitted 6*33840Skarels * provided that this notice is preserved and that due credit is given 7*33840Skarels * to the University of California at Berkeley. The name of the University 8*33840Skarels * may not be used to endorse or promote products derived from this 9*33840Skarels * software without specific prior written permission. This software 10*33840Skarels * is provided ``as is'' without express or implied warranty. 11*33840Skarels * 12*33840Skarels * @(#)in_cksum.c 7.1 (Berkeley) 03/29/88 13*33840Skarels */ 14*33840Skarels 15*33840Skarels #include "../h/types.h" 16*33840Skarels #include "../h/mbuf.h" 17*33840Skarels 18*33840Skarels /* 19*33840Skarels * Checksum routine for Internet Protocol family headers (Portable Version). 20*33840Skarels * 21*33840Skarels * This routine is very heavily used in the network 22*33840Skarels * code and should be modified for each CPU to be as fast as possible. 23*33840Skarels */ 24*33840Skarels 25*33840Skarels #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) 26*33840Skarels #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} 27*33840Skarels 28*33840Skarels in_cksum_c(m, len) 29*33840Skarels register struct mbuf *m; 30*33840Skarels register int len; 31*33840Skarels { 32*33840Skarels register u_short *w; 33*33840Skarels register int sum = 0; 34*33840Skarels register int mlen = 0; 35*33840Skarels int byte_swapped = 0; 36*33840Skarels 37*33840Skarels union { 38*33840Skarels char c[2]; 39*33840Skarels u_short s; 40*33840Skarels } s_util; 41*33840Skarels union { 42*33840Skarels u_short s[2]; 43*33840Skarels long l; 44*33840Skarels } l_util; 45*33840Skarels 46*33840Skarels for (;m && len; m = m->m_next) { 47*33840Skarels if (m->m_len == 0) 48*33840Skarels continue; 49*33840Skarels w = mtod(m, u_short *); 50*33840Skarels if (mlen == -1) { 51*33840Skarels /* 52*33840Skarels * The first byte of this mbuf is the continuation 53*33840Skarels * of a word spanning between this mbuf and the 54*33840Skarels * last mbuf. 55*33840Skarels * 56*33840Skarels * s_util.c[0] is already saved when scanning previous 57*33840Skarels * mbuf. 58*33840Skarels */ 59*33840Skarels s_util.c[1] = *(char *)w; 60*33840Skarels sum += s_util.s; 61*33840Skarels w = (u_short *)((char *)w + 1); 62*33840Skarels mlen = m->m_len - 1; 63*33840Skarels len--; 64*33840Skarels } else 65*33840Skarels mlen = m->m_len; 66*33840Skarels if (len < mlen) 67*33840Skarels mlen = len; 68*33840Skarels len -= mlen; 69*33840Skarels /* 70*33840Skarels * Force to even boundary. 71*33840Skarels */ 72*33840Skarels if ((1 & (int) w) && (mlen > 0)) { 73*33840Skarels REDUCE; 74*33840Skarels sum <<= 8; 75*33840Skarels s_util.c[0] = *(u_char *)w; 76*33840Skarels w = (u_short *)((char *)w + 1); 77*33840Skarels mlen--; 78*33840Skarels byte_swapped = 1; 79*33840Skarels } 80*33840Skarels /* 81*33840Skarels * Unroll the loop to make overhead from 82*33840Skarels * branches &c small. 83*33840Skarels */ 84*33840Skarels while ((mlen -= 32) >= 0) { 85*33840Skarels sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 86*33840Skarels sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; 87*33840Skarels sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; 88*33840Skarels sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; 89*33840Skarels w += 16; 90*33840Skarels } 91*33840Skarels mlen += 32; 92*33840Skarels while ((mlen -= 8) >= 0) { 93*33840Skarels sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; 94*33840Skarels w += 4; 95*33840Skarels } 96*33840Skarels mlen += 8; 97*33840Skarels if (mlen == 0 && byte_swapped == 0) 98*33840Skarels continue; 99*33840Skarels REDUCE; 100*33840Skarels while ((mlen -= 2) >= 0) { 101*33840Skarels sum += *w++; 102*33840Skarels } 103*33840Skarels if (byte_swapped) { 104*33840Skarels REDUCE; 105*33840Skarels sum <<= 8; 106*33840Skarels byte_swapped = 0; 107*33840Skarels if (mlen == -1) { 108*33840Skarels s_util.c[1] = *(char *)w; 109*33840Skarels sum += s_util.s; 110*33840Skarels mlen = 0; 111*33840Skarels } else 112*33840Skarels mlen = -1; 113*33840Skarels } else if (mlen == -1) 114*33840Skarels s_util.c[0] = *(char *)w; 115*33840Skarels } 116*33840Skarels if (len) 117*33840Skarels printf("cksum: out of data\n"); 118*33840Skarels if (mlen == -1) { 119*33840Skarels /* The last mbuf has odd # of bytes. Follow the 120*33840Skarels standard (the odd byte may be shifted left by 8 bits 121*33840Skarels or not as determined by endian-ness of the machine) */ 122*33840Skarels s_util.c[1] = 0; 123*33840Skarels sum += s_util.s; 124*33840Skarels } 125*33840Skarels REDUCE; 126*33840Skarels return (~sum & 0xffff); 127*33840Skarels } 128