projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 7c060394 MK |
1 | /* |
| 2 | * Copyright (c) 1988 Regents of the University of California. | |
| 3 | * All rights reserved. | |
| 4 | * | |
| dbf0c423 | 5 | * %sccs.include.redist.c% |
| 7c060394 | 6 | * |
| dbf0c423 | 7 | * @(#)in_cksum.c 7.3 (Berkeley) %G% |
| 7c060394 MK |
8 | */ |
| 9 | ||
| 10 | #include "../h/types.h" | |
| 11 | #include "../h/mbuf.h" | |
| 12 | ||
| 13 | /* | |
| 14 | * Checksum routine for Internet Protocol family headers (Portable Version). | |
| 15 | * | |
| 16 | * This routine is very heavily used in the network | |
| 17 | * code and should be modified for each CPU to be as fast as possible. | |
| 18 | */ | |
| 19 | ||
| 20 | #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) | |
| 21 | #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} | |
| 22 | ||
| 23 | in_cksum_c(m, len) | |
| 24 | register struct mbuf *m; | |
| 25 | register int len; | |
| 26 | { | |
| 27 | register u_short *w; | |
| 28 | register int sum = 0; | |
| 29 | register int mlen = 0; | |
| 30 | int byte_swapped = 0; | |
| 31 | ||
| 32 | union { | |
| 33 | char c[2]; | |
| 34 | u_short s; | |
| 35 | } s_util; | |
| 36 | union { | |
| 37 | u_short s[2]; | |
| 38 | long l; | |
| 39 | } l_util; | |
| 40 | ||
| 41 | for (;m && len; m = m->m_next) { | |
| 42 | if (m->m_len == 0) | |
| 43 | continue; | |
| 44 | w = mtod(m, u_short *); | |
| 45 | if (mlen == -1) { | |
| 46 | /* | |
| 47 | * The first byte of this mbuf is the continuation | |
| 48 | * of a word spanning between this mbuf and the | |
| 49 | * last mbuf. | |
| 50 | * | |
| 51 | * s_util.c[0] is already saved when scanning previous | |
| 52 | * mbuf. | |
| 53 | */ | |
| 54 | s_util.c[1] = *(char *)w; | |
| 55 | sum += s_util.s; | |
| 56 | w = (u_short *)((char *)w + 1); | |
| 57 | mlen = m->m_len - 1; | |
| 58 | len--; | |
| 59 | } else | |
| 60 | mlen = m->m_len; | |
| 61 | if (len < mlen) | |
| 62 | mlen = len; | |
| 63 | len -= mlen; | |
| 64 | /* | |
| 65 | * Force to even boundary. | |
| 66 | */ | |
| 67 | if ((1 & (int) w) && (mlen > 0)) { | |
| 68 | REDUCE; | |
| 69 | sum <<= 8; | |
| 70 | s_util.c[0] = *(u_char *)w; | |
| 71 | w = (u_short *)((char *)w + 1); | |
| 72 | mlen--; | |
| 73 | byte_swapped = 1; | |
| 74 | } | |
| 75 | /* | |
| 76 | * Unroll the loop to make overhead from | |
| 77 | * branches &c small. | |
| 78 | */ | |
| 79 | while ((mlen -= 32) >= 0) { | |
| 80 | sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; | |
| 81 | sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; | |
| 82 | sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; | |
| 83 | sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; | |
| 84 | w += 16; | |
| 85 | } | |
| 86 | mlen += 32; | |
| 87 | while ((mlen -= 8) >= 0) { | |
| 88 | sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; | |
| 89 | w += 4; | |
| 90 | } | |
| 91 | mlen += 8; | |
| 92 | if (mlen == 0 && byte_swapped == 0) | |
| 93 | continue; | |
| 94 | REDUCE; | |
| 95 | while ((mlen -= 2) >= 0) { | |
| 96 | sum += *w++; | |
| 97 | } | |
| 98 | if (byte_swapped) { | |
| 99 | REDUCE; | |
| 100 | sum <<= 8; | |
| 101 | byte_swapped = 0; | |
| 102 | if (mlen == -1) { | |
| 103 | s_util.c[1] = *(char *)w; | |
| 104 | sum += s_util.s; | |
| 105 | mlen = 0; | |
| 106 | } else | |
| 107 | mlen = -1; | |
| 108 | } else if (mlen == -1) | |
| 109 | s_util.c[0] = *(char *)w; | |
| 110 | } | |
| 111 | if (len) | |
| 112 | printf("cksum: out of data\n"); | |
| 113 | if (mlen == -1) { | |
| 114 | /* The last mbuf has odd # of bytes. Follow the | |
| 115 | standard (the odd byte may be shifted left by 8 bits | |
| 116 | or not as determined by endian-ness of the machine) */ | |
| 117 | s_util.c[1] = 0; | |
| 118 | sum += s_util.s; | |
| 119 | } | |
| 120 | REDUCE; | |
| 121 | return (~sum & 0xffff); | |
| 122 | } |