| /* |
| * Network checksum routines |
| * |
| * Copyright (C) 1999 Hewlett-Packard Co |
| * Copyright (C) 1999 Stephane Eranian <eranian@hpl.hp.com> |
| * |
| * Most of the code coming from arch/alpha/lib/checksum.c |
| * |
| * This file contains network checksum routines that are better done |
| * in an architecture-specific manner due to speed.. |
| */ |
| |
| #include <linux/string.h> |
| |
| #include <asm/byteorder.h> |
| |
| static inline unsigned short |
| from64to16(unsigned long x) |
| { |
| /* add up 32-bit words for 33 bits */ |
| x = (x & 0xffffffff) + (x >> 32); |
| /* add up 16-bit and 17-bit words for 17+c bits */ |
| x = (x & 0xffff) + (x >> 16); |
| /* add up 16-bit and 2-bit for 16+c bit */ |
| x = (x & 0xffff) + (x >> 16); |
| /* add up carry.. */ |
| x = (x & 0xffff) + (x >> 16); |
| return x; |
| } |
| |
| /* |
| * computes the checksum of the TCP/UDP pseudo-header |
| * returns a 16-bit checksum, already complemented. |
| */ |
| unsigned short int csum_tcpudp_magic(unsigned long saddr, |
| unsigned long daddr, |
| unsigned short len, |
| unsigned short proto, |
| unsigned int sum) |
| { |
| return ~from64to16(saddr + daddr + sum + |
| ((unsigned long) ntohs(len) << 16) + |
| ((unsigned long) proto << 8)); |
| } |
| |
| unsigned int csum_tcpudp_nofold(unsigned long saddr, |
| unsigned long daddr, |
| unsigned short len, |
| unsigned short proto, |
| unsigned int sum) |
| { |
| unsigned long result; |
| |
| result = (saddr + daddr + sum + |
| ((unsigned long) ntohs(len) << 16) + |
| ((unsigned long) proto << 8)); |
| |
| /* Fold down to 32-bits so we don't loose in the typedef-less network stack. */ |
| /* 64 to 33 */ |
| result = (result & 0xffffffff) + (result >> 32); |
| /* 33 to 32 */ |
| result = (result & 0xffffffff) + (result >> 32); |
| return result; |
| } |
| |
| extern unsigned long do_csum (const unsigned char *, long); |
| |
| /* |
| * computes the checksum of a memory block at buff, length len, |
| * and adds in "sum" (32-bit) |
| * |
| * returns a 32-bit number suitable for feeding into itself |
| * or csum_tcpudp_magic |
| * |
| * this function must be called with even lengths, except |
| * for the last fragment, which may be odd |
| * |
| * it's best to have buff aligned on a 32-bit boundary |
| */ |
| unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum) |
| { |
| unsigned long result = do_csum(buff, len); |
| |
| /* add in old sum, and carry.. */ |
| result += sum; |
| /* 32+c bits -> 32 bits */ |
| result = (result & 0xffffffff) + (result >> 32); |
| return result; |
| } |
| |
| |
| /* |
| * this routine is used for miscellaneous IP-like checksums, mainly |
| * in icmp.c |
| */ |
| unsigned short ip_compute_csum(unsigned char * buff, int len) |
| { |
| return ~do_csum(buff,len); |
| } |