// SPDX-License-Identifier: GPL-2.0
/*
 * arch/alpha/lib/checksum.c
 *
 * This file contains network checksum routines that are better done
 * in an architecture-specific manner due to speed..
 * Comments in other versions indicate that the algorithms are from RFC1071
 *
 * accelerated versions (and 21264 assembly versions ) contributed by
 *      Rick Gorton     <rick.gorton@alpha-processor.com>
 */
 
#include <linux/module.h>
#include <linux/string.h>
#include <net/checksum.h>

#include <asm/byteorder.h>
#include <asm/checksum.h>

static inline unsigned short from64to16(unsigned long x)
{
        /* Using extract instructions is a bit more efficient
           than the original shift/bitmask version.  */

        union {
                unsigned long   ul;
                unsigned int    ui[2];
                unsigned short  us[4];
        } in_v, tmp_v, out_v;

        in_v.ul = x;
        tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1];

        /* Since the bits of tmp_v.sh[3] are going to always be zero,
           we don't have to bother to add that in.  */
        out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1]
                        + (unsigned long) tmp_v.us[2];

        /* Similarly, out_v.us[2] is always zero for the final add.  */
        return out_v.us[0] + out_v.us[1];
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented.
 */
__sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
                          __u32 len, __u8 proto, __wsum sum)
{
        return (__force __sum16)~from64to16(
                (__force u64)saddr + (__force u64)daddr +
                (__force u64)sum + ((len + proto) << 8));
}
EXPORT_SYMBOL(csum_tcpudp_magic);

__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
                          __u32 len, __u8 proto, __wsum sum)
{
        unsigned long result;

        result = (__force u64)saddr + (__force u64)daddr +
                 (__force u64)sum + ((len + proto) << 8);

        /* Fold down to 32-bits so we don't lose in the typedef-less 
           network stack.  */
        /* 64 to 33 */
        result = (result & 0xffffffff) + (result >> 32);
        /* 33 to 32 */
        result = (result & 0xffffffff) + (result >> 32);
        return (__force __wsum)result;
}
EXPORT_SYMBOL(csum_tcpudp_nofold);

/*
 * Do a 64-bit checksum on an arbitrary memory area..
 *
 * This isn't a great routine, but it's not _horrible_ either. The
 * inner loop could be unrolled a bit further, and there are better
 * ways to do the carry, but this is reasonable.
 */
static inline unsigned long do_csum(const unsigned char * buff, int len)
{
        int odd, count;
        unsigned long result = 0;

        if (len <= 0)
                goto out;
        odd = 1 & (unsigned long) buff;
        if (odd) {
                result = *buff << 8;
                len--;
                buff++;
        }
        count = len >> 1;               /* nr of 16-bit words.. */
        if (count) {
                if (2 & (unsigned long) buff) {
                        result += *(unsigned short *) buff;
                        count--;
                        len -= 2;
                        buff += 2;
                }
                count >>= 1;            /* nr of 32-bit words.. */
                if (count) {
                        if (4 & (unsigned long) buff) {
                                result += *(unsigned int *) buff;
                                count--;
                                len -= 4;
                                buff += 4;
                        }
                        count >>= 1;    /* nr of 64-bit words.. */
                        if (count) {
                                unsigned long carry = 0;
                                do {
                                        unsigned long w = *(unsigned long *) buff;
                                        count--;
                                        buff += 8;
                                        result += carry;
                                        result += w;
                                        carry = (w > result);
                                } while (count);
                                result += carry;
                                result = (result & 0xffffffff) + (result >> 32);
                        }
                        if (len & 4) {
                                result += *(unsigned int *) buff;
                                buff += 4;
                        }
                }
                if (len & 2) {
                        result += *(unsigned short *) buff;
                        buff += 2;
                }
        }
        if (len & 1)
                result += *buff;
        result = from64to16(result);
        if (odd)
                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
out:
        return result;
}

/*
 *      This is a version of ip_compute_csum() optimized for IP headers,
 *      which always checksum on 4 octet boundaries.
 */
__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
        return (__force __sum16)~do_csum(iph,ihl*4);
}
EXPORT_SYMBOL(ip_fast_csum);

/*
 * 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
 */
__wsum csum_partial(const void *buff, int len, __wsum sum)
{
        unsigned long result = do_csum(buff, len);

        /* add in old sum, and carry.. */
        result += (__force u32)sum;
        /* 32+c bits -> 32 bits */
        result = (result & 0xffffffff) + (result >> 32);
        return (__force __wsum)result;
}

EXPORT_SYMBOL(csum_partial);

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */
__sum16 ip_compute_csum(const void *buff, int len)
{
        return (__force __sum16)~from64to16(do_csum(buff,len));
}
EXPORT_SYMBOL(ip_compute_csum);