Commit ed1f50c3 authored by Paul Durrant's avatar Paul Durrant Committed by David S. Miller
Browse files

net: add skb_checksum_setup 



This patch adds a function to set up the partial checksum offset for IP
packets (and optionally re-calculate the pseudo-header checksum) into the
core network code.
The implementation was previously private and duplicated between xen-netback
and xen-netfront, however it is not xen-specific and is potentially useful
to any network driver.

Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b86f81cc

include/linux/skbuff.h

+2 −0
Original line number Diff line number Diff line
@@ -2893,6 +2893,8 @@ static inline void skb_checksum_none_assert(const struct sk_buff *skb) 


bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);



int skb_checksum_setup(struct sk_buff *skb, bool recalculate);



u32 __skb_get_poff(const struct sk_buff *skb);



/**

net/core/skbuff.c

+273 −0
Original line number Diff line number Diff line
@@ -65,6 +65,7 @@ 
#include <net/dst.h>

#include <net/sock.h>

#include <net/checksum.h>

#include <net/ip6_checksum.h>

#include <net/xfrm.h>



#include <asm/uaccess.h>
@@ -3549,6 +3550,278 @@ bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off) 
}

EXPORT_SYMBOL_GPL(skb_partial_csum_set);



static int skb_maybe_pull_tail(struct sk_buff *skb, unsigned int len,

			       unsigned int max)

{

	if (skb_headlen(skb) >= len)

		return 0;



	/* If we need to pullup then pullup to the max, so we

	 * won't need to do it again.

	 */

	if (max > skb->len)

		max = skb->len;



	if (__pskb_pull_tail(skb, max - skb_headlen(skb)) == NULL)

		return -ENOMEM;



	if (skb_headlen(skb) < len)

		return -EPROTO;



	return 0;

}



/* This value should be large enough to cover a tagged ethernet header plus

 * maximally sized IP and TCP or UDP headers.

 */

#define MAX_IP_HDR_LEN 128



static int skb_checksum_setup_ip(struct sk_buff *skb, bool recalculate)

{

	unsigned int off;

	bool fragment;

	int err;



	fragment = false;



	err = skb_maybe_pull_tail(skb,

				  sizeof(struct iphdr),

				  MAX_IP_HDR_LEN);

	if (err < 0)

		goto out;



	if (ip_hdr(skb)->frag_off & htons(IP_OFFSET | IP_MF))

		fragment = true;



	off = ip_hdrlen(skb);



	err = -EPROTO;



	if (fragment)

		goto out;



	switch (ip_hdr(skb)->protocol) {

	case IPPROTO_TCP:

		err = skb_maybe_pull_tail(skb,

					  off + sizeof(struct tcphdr),

					  MAX_IP_HDR_LEN);

		if (err < 0)

			goto out;



		if (!skb_partial_csum_set(skb, off,

					  offsetof(struct tcphdr, check))) {

			err = -EPROTO;

			goto out;

		}



		if (recalculate)

			tcp_hdr(skb)->check =

				~csum_tcpudp_magic(ip_hdr(skb)->saddr,

						   ip_hdr(skb)->daddr,

						   skb->len - off,

						   IPPROTO_TCP, 0);

		break;

	case IPPROTO_UDP:

		err = skb_maybe_pull_tail(skb,

					  off + sizeof(struct udphdr),

					  MAX_IP_HDR_LEN);

		if (err < 0)

			goto out;



		if (!skb_partial_csum_set(skb, off,

					  offsetof(struct udphdr, check))) {

			err = -EPROTO;

			goto out;

		}



		if (recalculate)

			udp_hdr(skb)->check =

				~csum_tcpudp_magic(ip_hdr(skb)->saddr,

						   ip_hdr(skb)->daddr,

						   skb->len - off,

						   IPPROTO_UDP, 0);

		break;

	default:

		goto out;

	}



	err = 0;



out:

	return err;

}



/* This value should be large enough to cover a tagged ethernet header plus

 * an IPv6 header, all options, and a maximal TCP or UDP header.

 */

#define MAX_IPV6_HDR_LEN 256



#define OPT_HDR(type, skb, off) \

	(type *)(skb_network_header(skb) + (off))



static int skb_checksum_setup_ipv6(struct sk_buff *skb, bool recalculate)

{

	int err;

	u8 nexthdr;

	unsigned int off;

	unsigned int len;

	bool fragment;

	bool done;



	fragment = false;

	done = false;



	off = sizeof(struct ipv6hdr);



	err = skb_maybe_pull_tail(skb, off, MAX_IPV6_HDR_LEN);

	if (err < 0)

		goto out;



	nexthdr = ipv6_hdr(skb)->nexthdr;



	len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);

	while (off <= len && !done) {

		switch (nexthdr) {

		case IPPROTO_DSTOPTS:

		case IPPROTO_HOPOPTS:

		case IPPROTO_ROUTING: {

			struct ipv6_opt_hdr *hp;



			err = skb_maybe_pull_tail(skb,

						  off +

						  sizeof(struct ipv6_opt_hdr),

						  MAX_IPV6_HDR_LEN);

			if (err < 0)

				goto out;



			hp = OPT_HDR(struct ipv6_opt_hdr, skb, off);

			nexthdr = hp->nexthdr;

			off += ipv6_optlen(hp);

			break;

		}

		case IPPROTO_AH: {

			struct ip_auth_hdr *hp;



			err = skb_maybe_pull_tail(skb,

						  off +

						  sizeof(struct ip_auth_hdr),

						  MAX_IPV6_HDR_LEN);

			if (err < 0)

				goto out;



			hp = OPT_HDR(struct ip_auth_hdr, skb, off);

			nexthdr = hp->nexthdr;

			off += ipv6_authlen(hp);

			break;

		}

		case IPPROTO_FRAGMENT: {

			struct frag_hdr *hp;



			err = skb_maybe_pull_tail(skb,

						  off +

						  sizeof(struct frag_hdr),

						  MAX_IPV6_HDR_LEN);

			if (err < 0)

				goto out;



			hp = OPT_HDR(struct frag_hdr, skb, off);



			if (hp->frag_off & htons(IP6_OFFSET | IP6_MF))

				fragment = true;



			nexthdr = hp->nexthdr;

			off += sizeof(struct frag_hdr);

			break;

		}

		default:

			done = true;

			break;

		}

	}



	err = -EPROTO;



	if (!done || fragment)

		goto out;



	switch (nexthdr) {

	case IPPROTO_TCP:

		err = skb_maybe_pull_tail(skb,

					  off + sizeof(struct tcphdr),

					  MAX_IPV6_HDR_LEN);

		if (err < 0)

			goto out;



		if (!skb_partial_csum_set(skb, off,

					  offsetof(struct tcphdr, check))) {

			err = -EPROTO;

			goto out;

		}



		if (recalculate)

			tcp_hdr(skb)->check =

				~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,

						 &ipv6_hdr(skb)->daddr,

						 skb->len - off,

						 IPPROTO_TCP, 0);

		break;

	case IPPROTO_UDP:

		err = skb_maybe_pull_tail(skb,

					  off + sizeof(struct udphdr),

					  MAX_IPV6_HDR_LEN);

		if (err < 0)

			goto out;



		if (!skb_partial_csum_set(skb, off,

					  offsetof(struct udphdr, check))) {

			err = -EPROTO;

			goto out;

		}



		if (recalculate)

			udp_hdr(skb)->check =

				~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,

						 &ipv6_hdr(skb)->daddr,

						 skb->len - off,

						 IPPROTO_UDP, 0);

		break;

	default:

		goto out;

	}



	err = 0;



out:

	return err;

}



/**

 * skb_checksum_setup - set up partial checksum offset

 * @skb: the skb to set up

 * @recalculate: if true the pseudo-header checksum will be recalculated

 */

int skb_checksum_setup(struct sk_buff *skb, bool recalculate)

{

	int err;



	switch (skb->protocol) {

	case htons(ETH_P_IP):

		err = skb_checksum_setup_ip(skb, recalculate);

		break;



	case htons(ETH_P_IPV6):

		err = skb_checksum_setup_ipv6(skb, recalculate);

		break;



	default:

		err = -EPROTO;

		break;

	}



	return err;

}

EXPORT_SYMBOL(skb_checksum_setup);



void __skb_warn_lro_forwarding(const struct sk_buff *skb)

{

	net_warn_ratelimited("%s: received packets cannot be forwarded while LRO is enabled\n",

CRA Git | Maintained and supported by SUSTech CRA and CCSE