| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Network checksum routines |
| 3 | * |
| 4 | * Copyright (C) 1999, 2003 Hewlett-Packard Co |
| 5 | * Stephane Eranian <eranian@hpl.hp.com> |
| 6 | * |
| 7 | * Most of the code coming from arch/alpha/lib/checksum.c |
| 8 | * |
| 9 | * This file contains network checksum routines that are better done |
| 10 | * in an architecture-specific manner due to speed.. |
| 11 | */ |
| 12 | |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/string.h> |
| 15 | |
| 16 | #include <asm/byteorder.h> |
| 17 | |
| 18 | static inline unsigned short |
| 19 | from64to16 (unsigned long x) |
| 20 | { |
| 21 | /* add up 32-bit words for 33 bits */ |
| 22 | x = (x & 0xffffffff) + (x >> 32); |
| 23 | /* add up 16-bit and 17-bit words for 17+c bits */ |
| 24 | x = (x & 0xffff) + (x >> 16); |
| 25 | /* add up 16-bit and 2-bit for 16+c bit */ |
| 26 | x = (x & 0xffff) + (x >> 16); |
| 27 | /* add up carry.. */ |
| 28 | x = (x & 0xffff) + (x >> 16); |
| 29 | return x; |
| 30 | } |
| 31 | |
| 32 | /* |
| 33 | * computes the checksum of the TCP/UDP pseudo-header |
| 34 | * returns a 16-bit checksum, already complemented. |
| 35 | */ |
| 36 | unsigned short int |
| 37 | csum_tcpudp_magic (unsigned long saddr, unsigned long daddr, unsigned short len, |
| 38 | unsigned short proto, unsigned int sum) |
| 39 | { |
| 40 | return ~from64to16(saddr + daddr + sum + ((unsigned long) ntohs(len) << 16) + |
| 41 | ((unsigned long) proto << 8)); |
| 42 | } |
| 43 | |
| 44 | EXPORT_SYMBOL(csum_tcpudp_magic); |
| 45 | |
| 46 | unsigned int |
| 47 | csum_tcpudp_nofold (unsigned long saddr, unsigned long daddr, unsigned short len, |
| 48 | unsigned short proto, unsigned int sum) |
| 49 | { |
| 50 | unsigned long result; |
| 51 | |
| 52 | result = (saddr + daddr + sum + |
| 53 | ((unsigned long) ntohs(len) << 16) + |
| 54 | ((unsigned long) proto << 8)); |
| 55 | |
| 56 | /* Fold down to 32-bits so we don't lose in the typedef-less network stack. */ |
| 57 | /* 64 to 33 */ |
| 58 | result = (result & 0xffffffff) + (result >> 32); |
| 59 | /* 33 to 32 */ |
| 60 | result = (result & 0xffffffff) + (result >> 32); |
| 61 | return result; |
| 62 | } |
| 63 | |
| 64 | extern unsigned long do_csum (const unsigned char *, long); |
| 65 | |
| 66 | /* |
| 67 | * computes the checksum of a memory block at buff, length len, |
| 68 | * and adds in "sum" (32-bit) |
| 69 | * |
| 70 | * returns a 32-bit number suitable for feeding into itself |
| 71 | * or csum_tcpudp_magic |
| 72 | * |
| 73 | * this function must be called with even lengths, except |
| 74 | * for the last fragment, which may be odd |
| 75 | * |
| 76 | * it's best to have buff aligned on a 32-bit boundary |
| 77 | */ |
| 78 | unsigned int |
| 79 | csum_partial (const unsigned char * buff, int len, unsigned int sum) |
| 80 | { |
| 81 | unsigned long result = do_csum(buff, len); |
| 82 | |
| 83 | /* add in old sum, and carry.. */ |
| 84 | result += sum; |
| 85 | /* 32+c bits -> 32 bits */ |
| 86 | result = (result & 0xffffffff) + (result >> 32); |
| 87 | return result; |
| 88 | } |
| 89 | |
| 90 | EXPORT_SYMBOL(csum_partial); |
| 91 | |
| 92 | /* |
| 93 | * this routine is used for miscellaneous IP-like checksums, mainly |
| 94 | * in icmp.c |
| 95 | */ |
| 96 | unsigned short |
| 97 | ip_compute_csum (unsigned char * buff, int len) |
| 98 | { |
| 99 | return ~do_csum(buff,len); |
| 100 | } |
| 101 | |
| 102 | EXPORT_SYMBOL(ip_compute_csum); |