C++ csum_partial函数代码示例

static int tcf_csum_ipv4_igmp(struct sk_buff *skb,
			      unsigned int ihl, unsigned int ipl)
{
	struct igmphdr *igmph;

	igmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*igmph));
	if (igmph == NULL)
		return 0;

	igmph->csum = 0;
	skb->csum = csum_partial(igmph, ipl - ihl, 0);
	igmph->csum = csum_fold(skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

static int dccp_v4_verify_checksum(struct sk_buff *skb,
				   const __be32 saddr, const __be32 daddr)
{
	struct dccp_hdr *dh = dccp_hdr(skb);
	int checksum_len;
	u32 tmp;

	if (dh->dccph_cscov == 0)
		checksum_len = skb->len;
	else {
		checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
		checksum_len = checksum_len < skb->len ? checksum_len :
							 skb->len;
	}
	tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
	return csum_tcpudp_magic(saddr, daddr, checksum_len,
				 IPPROTO_DCCP, tmp) == 0 ? 0 : -1;
}

void os_info_check(struct os_info *os_info)
{
	if (os_info == NULL)
		kdump_failed(EOS_INFO_MISSING);
	if (((unsigned long) os_info) % PAGE_SIZE)
		kdump_failed(EOS_INFO_MISSING);
	if (!page_is_valid((unsigned long) os_info))
		kdump_failed(EOS_INFO_MISSING);
	if (os_info->magic != OS_INFO_MAGIC)
		kdump_failed(EOS_INFO_MISSING);
	if (csum_partial(&os_info->version_major, OS_INF0_CSUM_SIZE, 0) !=
	    os_info->csum)
		kdump_failed(EOS_INFO_CSUM_FAILED);
	if (os_info->version_major > OS_INFO_VERSION_MAJOR_SUPPORTED)
		kdump_failed(EOS_INFO_VERSION);
	if (os_info->crashkernel_addr == 0)
		kdump_failed(EOS_INFO_NOCRASHKERNEL);
}

/* Compute the whole skb csum in s/w and store it, then verify GRO csum
 * starting from gro_offset.
 */
static __sum16 gro_skb_checksum(struct sk_buff *skb)
{
	__sum16 sum;

	skb->csum = skb_checksum(skb, 0, skb->len, 0);
	NAPI_GRO_CB(skb)->csum = csum_sub(skb->csum,
		csum_partial(skb->data, skb_gro_offset(skb), 0));
	sum = csum_fold(NAPI_GRO_CB(skb)->csum);
	if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE)) {
		if (unlikely(!sum) && !skb->csum_complete_sw)
			netdev_rx_csum_fault(skb->dev);
	} else {
		skb->ip_summed = CHECKSUM_COMPLETE;
		skb->csum_complete_sw = 1;
	}

	return sum;
}

static int push_vlan(struct sk_buff *skb, const struct ovs_action_push_vlan *vlan)
{
	if (unlikely(vlan_tx_tag_present(skb))) {
		u16 current_tag;

		/* push down current VLAN tag */
		current_tag = vlan_tx_tag_get(skb);

		if (!__vlan_put_tag(skb, current_tag))
			return -ENOMEM;

		if (get_ip_summed(skb) == OVS_CSUM_COMPLETE)
			skb->csum = csum_add(skb->csum, csum_partial(skb->data
					+ ETH_HLEN, VLAN_HLEN, 0));

	}
	__vlan_hwaccel_put_tag(skb, ntohs(vlan->vlan_tci) & ~VLAN_TAG_PRESENT);
	return 0;
}

/* validate checksum of entire packet */
void csum_network_interface::test4(void)
{
    /* we produced */
    unsigned char pkt[]={
        /* pseudo header */
        0xfe,0x80,0x00,0x00,0x00,0x00,0x00,0x00,
        0x02,0x16,0x3e,0xff,0xfe,0x11,0x34,0x24,
        0xff,0x02,0x00,0x00,0x00,0x00,0x00,0x00,
        0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,
        0x00,0x00,0x00,0x18,0x00,0x00,0x00,0x3a,
        /* icmp payload */
        0x9b, 0x02, 0x39, 0x8d, 0x01, 0x40, 0x00, 0x01,
        0x70, 0x61, 0x6e, 0x64, 0x6f, 0x72, 0x61, 0x20,
        0x69, 0x73, 0x20, 0x66, 0x75, 0x6e, 0x0a, 0x6c
    };

    unsigned short result = csum_partial(pkt, sizeof(pkt), 0);
    result = (~result & 0xffff);
    assert(result == 0);
}

void tcp_send_check(struct sk_buff *skb) {
	if (skb_is_nonlinear(skb)) {
		skb_linearize(skb);
	}
	struct iphdr *ip_header = ip_hdr(skb);
	struct tcphdr *tcp_header = tcp_hdr(skb);
	unsigned int tcp_header_length = (skb->len - (ip_header->ihl << 2));
	tcp_header->check = 0;
	tcp_header->check = tcp_v4_check(
		tcp_header_length,
		ip_header->saddr,
		ip_header->daddr,
		csum_partial(
			(char*)tcp_header,
			tcp_header_length,
			0
		)
	);
	skb->ip_summed = CHECKSUM_NONE;
}

/* validate calculation of pseudo-header */
void csum_network_interface::test3(void)
{
    struct ip6_hdr v6;
    unsigned char src[]={
        0xfe, 0x80, 0,    0,    0,    0,    0,    0,
        0x2,  0x16, 0x3e, 0xff, 0xfe, 0x11, 0x34, 0x24
    };
    unsigned char dst[]={
        0xff, 0x02, 0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    1
    };

    memcpy(&v6.ip6_src.s6_addr, src, 16);
    memcpy(&v6.ip6_dst.s6_addr, dst, 16);
    unsigned int icmp_len = 24;


    // 0000: fe 80 00 00  00 00 00 00  02 16 3e ff  fe 11 34 24
    // 0010: ff 02 00 00  00 00 00 00  00 00 00 00  00 00 00 01
    // 0020: 00 00 00 18  00 00 00 3a

    unsigned short icmp6sum = csum_ipv6_magic(&v6.ip6_src,
                                              &v6.ip6_dst,
                                              icmp_len, IPPROTO_ICMPV6,
                                              0);
    icmp6sum = (~icmp6sum & 0xffff);

    unsigned char all[]={
        0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x02, 0x16, 0x3e, 0xff, 0xfe, 0x11, 0x34, 0x24,
        0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
        0x00, 0x00, 0x00, 0x18, 0x00, 0x00, 0x00, 0x3a
    };
    unsigned short result2 = csum_partial(all, 5*8, 0);
    result2 = (~result2 & 0xffff);

    printf("result2=%04x\n",result2);
    assert(result2 == htons(0x8edd));
    assert(icmp6sum == result2);
}

static int push_vlan(struct sk_buff *skb, const struct ovs_action_push_vlan *vlan)
{
	if (unlikely(vlan_tx_tag_present(skb))) {
		u16 current_tag;

		/* push down current VLAN tag */
		current_tag = vlan_tx_tag_get(skb);

		skb = vlan_insert_tag_set_proto(skb, skb->vlan_proto,
						current_tag);
		if (!skb)
			return -ENOMEM;

		if (skb->ip_summed == CHECKSUM_COMPLETE)
			skb->csum = csum_add(skb->csum, csum_partial(skb->data
					+ (2 * ETH_ALEN), VLAN_HLEN, 0));

	}
	__vlan_hwaccel_put_tag(skb, vlan->vlan_tpid, ntohs(vlan->vlan_tci) & ~VLAN_TAG_PRESENT);
	return 0;
}

static int tcf_csum_ipv6_tcp(struct sk_buff *skb,
			     unsigned int ihl, unsigned int ipl)
{
	struct tcphdr *tcph;
	const struct ipv6hdr *ip6h;

	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
	if (tcph == NULL)
		return 0;

	ip6h = ipv6_hdr(skb);
	tcph->check = 0;
	skb->csum = csum_partial(tcph, ipl - ihl, 0);
	tcph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
				      ipl - ihl, IPPROTO_TCP,
				      skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
			      const struct sk_buff *oldskb,
			      const struct tcphdr *oth, unsigned int otcplen)
{
	struct tcphdr *tcph;
	int needs_ack;

	skb_reset_transport_header(nskb);
	tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
	/* Truncate to length (no data) */
	tcph->doff = sizeof(struct tcphdr)/4;
	tcph->source = oth->dest;
	tcph->dest = oth->source;

	if (oth->ack) {
		needs_ack = 0;
		tcph->seq = oth->ack_seq;
		tcph->ack_seq = 0;
	} else {
		needs_ack = 1;
		tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
				      otcplen - (oth->doff<<2));
		tcph->seq = 0;
	}

	/* Reset flags */
	((u_int8_t *)tcph)[13] = 0;
	tcph->rst = 1;
	tcph->ack = needs_ack;
	tcph->window = 0;
	tcph->urg_ptr = 0;
	tcph->check = 0;

	/* Adjust TCP checksum */
	tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
				      &ipv6_hdr(nskb)->daddr,
				      sizeof(struct tcphdr), IPPROTO_TCP,
				      csum_partial(tcph,
						   sizeof(struct tcphdr), 0));
}

__wsum csum_and_copy_from_user(const void __user *src, void *dst,
			       int len, __wsum sum, int *err_ptr)
{
	unsigned int csum;

	might_sleep();

	*err_ptr = 0;

	if (!len) {
		csum = 0;
		goto out;
	}

	if (unlikely((len < 0) || !access_ok(VERIFY_READ, src, len))) {
		*err_ptr = -EFAULT;
		csum = (__force unsigned int)sum;
		goto out;
	}

	csum = csum_partial_copy_generic((void __force *)src, dst,
					 len, sum, err_ptr, NULL);

	if (unlikely(*err_ptr)) {
		int missing = __copy_from_user(dst, src, len);

		if (missing) {
			memset(dst + len - missing, 0, missing);
			*err_ptr = -EFAULT;
		} else {
			*err_ptr = 0;
		}

		csum = csum_partial(dst, len, sum);
	}

out:
	return (__force __wsum)csum;
}

static bool ipv6_validate_packet_len(struct sk_buff *skb_in, struct sk_buff *skb_out)
{
	struct ipv6hdr *ip6_hdr = ipv6_hdr(skb_out);
	struct hdr_iterator iterator = HDR_ITERATOR_INIT(ip6_hdr);
	unsigned int ipv6_mtu;
	unsigned int ipv4_mtu;

	if (skb_out->len <= skb_out->dev->mtu)
		return true;

	hdr_iterator_last(&iterator);
	if (iterator.hdr_type == IPPROTO_ICMPV6) {
		struct icmp6hdr *icmpv6_hdr = icmp6_hdr(skb_out);
		if (is_icmp6_error(icmpv6_hdr->icmp6_type)) {
			int new_packet_len = skb_out->dev->mtu;
			int l3_payload_len = new_packet_len - (iterator.data - (void *) ip6_hdr);

			skb_trim(skb_out, new_packet_len);

			ip6_hdr->payload_len = cpu_to_be16(l3_payload_len);

			icmpv6_hdr->icmp6_cksum = 0;
			icmpv6_hdr->icmp6_cksum = csum_ipv6_magic(&ip6_hdr->saddr, &ip6_hdr->daddr,
					l3_payload_len, IPPROTO_ICMPV6, csum_partial(icmpv6_hdr, l3_payload_len, 0));

			return true;
		}
	}

	ipv6_mtu = skb_out->dev->mtu;
	ipv4_mtu = skb_in->dev->mtu;

	log_debug("Packet is too large for the outgoing MTU and IPv6 routers don't do fragmentation. "
			"Dropping...");
	icmp_send(skb_in, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
			cpu_to_be32(min_uint(ipv6_mtu, ipv4_mtu + 20)));
	return false;
}

/**
 *	skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.
 *	@skb: skbuff
 *	@hlen: hardware length
 *	@iov: io vector
 *
 *	Caller _must_ check that skb will fit to this iovec.
 *
 *	Returns: 0       - success.
 *		 -EINVAL - checksum failure.
 *		 -EFAULT - fault during copy. Beware, in this case iovec
 *			   can be modified!
 */
int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
				     int hlen, struct iovec *iov)
{
	__wsum csum;
	int chunk = skb->len - hlen;

	if (!chunk)
		return 0;

	/* Skip filled elements.
	 * Pretty silly, look at memcpy_toiovec, though 8)
	 */
	while (!iov->iov_len)
		iov++;

	if (iov->iov_len < chunk) {
		if (__skb_checksum_complete(skb))
			goto csum_error;
		if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
			goto fault;
	} else {
		csum = csum_partial(skb->data, hlen, skb->csum);
		if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
					       chunk, &csum))
			goto fault;
		if (csum_fold(csum))
			goto csum_error;
		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
			netdev_rx_csum_fault(skb->dev);
		iov->iov_len -= chunk;
		iov->iov_base += chunk;
	}
	return 0;
csum_error:
	return -EINVAL;
fault:
	return -EFAULT;
}

/* set ECT codepoint from IP header.
 * 	return 0 if there was an error. */
static inline int
set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo)
{
	if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK)
	    != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
		u_int16_t diffs[2];

		if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))
			return 0;

		diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
		(*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK;
		(*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
		diffs[1] = htons((*pskb)->nh.iph->tos);
		(*pskb)->nh.iph->check
			= csum_fold(csum_partial((char *)diffs,
						 sizeof(diffs),
						 (*pskb)->nh.iph->check
						 ^0xFFFF));
		(*pskb)->nfcache |= NFC_ALTERED;
	} 
	return 1;
}