99f0b958b1
When changing one 16bit value by another in IP header, we can adjust the IP checksum by doing a simple operation described in RFC 1624, as reminded by David. csum_partial() is a complex function on x86_64, not really suited for small number of checksummed bytes. I spotted csum_partial() being in the top 20 most consuming functions (more than 1 %) in a GRO workload, which was rather unexpected. The caller was inet_gro_complete() doing a csum_replace2() when building the new IP header for the GRO packet. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
155 lines
3.9 KiB
C
155 lines
3.9 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Checksumming functions for IP, TCP, UDP and so on
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*
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* Authors: Jorge Cwik, <jorge@laser.satlink.net>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Borrows very liberally from tcp.c and ip.c, see those
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* files for more names.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#ifndef _CHECKSUM_H
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#define _CHECKSUM_H
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#include <linux/errno.h>
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#include <asm/types.h>
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#include <asm/byteorder.h>
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#include <asm/uaccess.h>
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#include <asm/checksum.h>
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#ifndef _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
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static inline
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__wsum csum_and_copy_from_user (const void __user *src, void *dst,
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int len, __wsum sum, int *err_ptr)
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{
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if (access_ok(VERIFY_READ, src, len))
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return csum_partial_copy_from_user(src, dst, len, sum, err_ptr);
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if (len)
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*err_ptr = -EFAULT;
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return sum;
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}
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#endif
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#ifndef HAVE_CSUM_COPY_USER
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static __inline__ __wsum csum_and_copy_to_user
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(const void *src, void __user *dst, int len, __wsum sum, int *err_ptr)
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{
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sum = csum_partial(src, len, sum);
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if (access_ok(VERIFY_WRITE, dst, len)) {
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if (copy_to_user(dst, src, len) == 0)
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return sum;
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}
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if (len)
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*err_ptr = -EFAULT;
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return (__force __wsum)-1; /* invalid checksum */
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}
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#endif
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static inline __wsum csum_add(__wsum csum, __wsum addend)
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{
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u32 res = (__force u32)csum;
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res += (__force u32)addend;
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return (__force __wsum)(res + (res < (__force u32)addend));
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}
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static inline __wsum csum_sub(__wsum csum, __wsum addend)
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{
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return csum_add(csum, ~addend);
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}
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static inline __sum16 csum16_add(__sum16 csum, __be16 addend)
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{
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u16 res = (__force u16)csum;
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res += (__force u16)addend;
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return (__force __sum16)(res + (res < (__force u16)addend));
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}
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static inline __sum16 csum16_sub(__sum16 csum, __be16 addend)
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{
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return csum16_add(csum, ~addend);
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}
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static inline __wsum
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csum_block_add(__wsum csum, __wsum csum2, int offset)
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{
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u32 sum = (__force u32)csum2;
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if (offset&1)
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sum = ((sum&0xFF00FF)<<8)+((sum>>8)&0xFF00FF);
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return csum_add(csum, (__force __wsum)sum);
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}
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static inline __wsum
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csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)
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{
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return csum_block_add(csum, csum2, offset);
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}
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static inline __wsum
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csum_block_sub(__wsum csum, __wsum csum2, int offset)
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{
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u32 sum = (__force u32)csum2;
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if (offset&1)
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sum = ((sum&0xFF00FF)<<8)+((sum>>8)&0xFF00FF);
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return csum_sub(csum, (__force __wsum)sum);
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}
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static inline __wsum csum_unfold(__sum16 n)
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{
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return (__force __wsum)n;
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}
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static inline __wsum csum_partial_ext(const void *buff, int len, __wsum sum)
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{
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return csum_partial(buff, len, sum);
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}
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#define CSUM_MANGLED_0 ((__force __sum16)0xffff)
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static inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
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{
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__be32 diff[] = { ~from, to };
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*sum = csum_fold(csum_partial(diff, sizeof(diff), ~csum_unfold(*sum)));
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}
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/* Implements RFC 1624 (Incremental Internet Checksum)
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* 3. Discussion states :
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* HC' = ~(~HC + ~m + m')
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* m : old value of a 16bit field
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* m' : new value of a 16bit field
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*/
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static inline void csum_replace2(__sum16 *sum, __be16 old, __be16 new)
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{
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*sum = ~csum16_add(csum16_sub(~(*sum), old), new);
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}
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struct sk_buff;
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void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
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__be32 from, __be32 to, int pseudohdr);
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void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
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const __be32 *from, const __be32 *to,
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int pseudohdr);
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static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
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__be16 from, __be16 to,
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int pseudohdr)
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{
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inet_proto_csum_replace4(sum, skb, (__force __be32)from,
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(__force __be32)to, pseudohdr);
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}
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#endif
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