1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Network checksum routines 4 * 5 * Copyright (C) 1999, 2003 Hewlett-Packard Co 6 * Stephane Eranian <eranian@hpl.hp.com> 7 * 8 * Most of the code coming from arch/alpha/lib/checksum.c 9 * 10 * This file contains network checksum routines that are better done 11 * in an architecture-specific manner due to speed.. 12 */ 13 14 #include <linux/module.h> 15 #include <linux/string.h> 16 17 #include <asm/byteorder.h> 18 19 static inline unsigned short 20 from64to16 (unsigned long x) 21 { 22 /* add up 32-bit words for 33 bits */ 23 x = (x & 0xffffffff) + (x >> 32); 24 /* add up 16-bit and 17-bit words for 17+c bits */ 25 x = (x & 0xffff) + (x >> 16); 26 /* add up 16-bit and 2-bit for 16+c bit */ 27 x = (x & 0xffff) + (x >> 16); 28 /* add up carry.. */ 29 x = (x & 0xffff) + (x >> 16); 30 return x; 31 } 32 33 /* 34 * computes the checksum of the TCP/UDP pseudo-header 35 * returns a 16-bit checksum, already complemented. 36 */ 37 __sum16 38 csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len, 39 __u8 proto, __wsum sum) 40 { 41 return (__force __sum16)~from64to16( 42 (__force u64)saddr + (__force u64)daddr + 43 (__force u64)sum + ((len + proto) << 8)); 44 } 45 46 EXPORT_SYMBOL(csum_tcpudp_magic); 47 48 __wsum 49 csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len, 50 __u8 proto, __wsum sum) 51 { 52 unsigned long result; 53 54 result = (__force u64)saddr + (__force u64)daddr + 55 (__force u64)sum + ((len + proto) << 8); 56 57 /* Fold down to 32-bits so we don't lose in the typedef-less network stack. */ 58 /* 64 to 33 */ 59 result = (result & 0xffffffff) + (result >> 32); 60 /* 33 to 32 */ 61 result = (result & 0xffffffff) + (result >> 32); 62 return (__force __wsum)result; 63 } 64 EXPORT_SYMBOL(csum_tcpudp_nofold); 65 66 extern unsigned long do_csum (const unsigned char *, long); 67 68 /* 69 * computes the checksum of a memory block at buff, length len, 70 * and adds in "sum" (32-bit) 71 * 72 * returns a 32-bit number suitable for feeding into itself 73 * or csum_tcpudp_magic 74 * 75 * this function must be called with even lengths, except 76 * for the last fragment, which may be odd 77 * 78 * it's best to have buff aligned on a 32-bit boundary 79 */ 80 __wsum csum_partial(const void *buff, int len, __wsum sum) 81 { 82 u64 result = do_csum(buff, len); 83 84 /* add in old sum, and carry.. */ 85 result += (__force u32)sum; 86 /* 32+c bits -> 32 bits */ 87 result = (result & 0xffffffff) + (result >> 32); 88 return (__force __wsum)result; 89 } 90 91 EXPORT_SYMBOL(csum_partial); 92 93 /* 94 * this routine is used for miscellaneous IP-like checksums, mainly 95 * in icmp.c 96 */ 97 __sum16 ip_compute_csum (const void *buff, int len) 98 { 99 return (__force __sum16)~do_csum(buff,len); 100 } 101 102 EXPORT_SYMBOL(ip_compute_csum); 103