net/ipv4/netfilter.c - kernel/skids - Git at Google

 /* IPv4 specific functions of netfilter core */
 #include <linux/kernel.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv4.h>
 #include <linux/ip.h>
 #include <linux/skbuff.h>
 #include <linux/gfp.h>
 #include <net/route.h>
 #include <net/xfrm.h>
 #include <net/ip.h>
 #include <net/netfilter/nf_queue.h>

 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 {
 	struct net *net = dev_net(skb_dst(skb)->dev);
 	const struct iphdr *iph = ip_hdr(skb);
 	struct rtable *rt;
 	struct flowi fl = {};
 	unsigned long orefdst;
 	unsigned int hh_len;
 	unsigned int type;

 	type = inet_addr_type(net, iph->saddr);
 	if (skb->sk && inet_sk(skb->sk)->transparent)
 		type = RTN_LOCAL;
 	if (addr_type == RTN_UNSPEC)
 		addr_type = type;

 	/* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
 	 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
 	 */
 	if (addr_type == RTN_LOCAL) {
 		fl.nl_u.ip4_u.daddr = iph->daddr;
 		if (type == RTN_LOCAL)
 			fl.nl_u.ip4_u.saddr = iph->saddr;
 		fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
 		fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
 		fl.mark = skb->mark;
 		fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
 		if (ip_route_output_key(net, &rt, &fl) != 0)
 			return -1;

 		/* Drop old route. */
 		skb_dst_drop(skb);
 		skb_dst_set(skb, &rt->u.dst);
 	} else {
 		/* non-local src, find valid iif to satisfy
 		 * rp-filter when calling ip_route_input. */
 		fl.nl_u.ip4_u.daddr = iph->saddr;
 		if (ip_route_output_key(net, &rt, &fl) != 0)
 			return -1;

 		orefdst = skb->_skb_refdst;
 		if (ip_route_input(skb, iph->daddr, iph->saddr,
 				   RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
 			dst_release(&rt->u.dst);
 			return -1;
 		}
 		dst_release(&rt->u.dst);
 		refdst_drop(orefdst);
 	}

 	if (skb_dst(skb)->error)
 		return -1;

 #ifdef CONFIG_XFRM
 	if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
 	    xfrm_decode_session(skb, &fl, AF_INET) == 0) {
 		struct dst_entry *dst = skb_dst(skb);
 		skb_dst_set(skb, NULL);
 		if (xfrm_lookup(net, &dst, &fl, skb->sk, 0))
 			return -1;
 		skb_dst_set(skb, dst);
 	}
 #endif

 	/* Change in oif may mean change in hh_len. */
 	hh_len = skb_dst(skb)->dev->hard_header_len;
 	if (skb_headroom(skb) < hh_len &&
 	    pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
 		return -1;

 	return 0;
 }
 EXPORT_SYMBOL(ip_route_me_harder);

 #ifdef CONFIG_XFRM
 int ip_xfrm_me_harder(struct sk_buff *skb)
 {
 	struct flowi fl;
 	unsigned int hh_len;
 	struct dst_entry *dst;

 	if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
 		return 0;
 	if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
 		return -1;

 	dst = skb_dst(skb);
 	if (dst->xfrm)
 		dst = ((struct xfrm_dst *)dst)->route;
 	dst_hold(dst);

 	if (xfrm_lookup(dev_net(dst->dev), &dst, &fl, skb->sk, 0) < 0)
 		return -1;

 	skb_dst_drop(skb);
 	skb_dst_set(skb, dst);

 	/* Change in oif may mean change in hh_len. */
 	hh_len = skb_dst(skb)->dev->hard_header_len;
 	if (skb_headroom(skb) < hh_len &&
 	    pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
 		return -1;
 	return 0;
 }
 EXPORT_SYMBOL(ip_xfrm_me_harder);
 #endif

 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
 EXPORT_SYMBOL(ip_nat_decode_session);

 /*
  * Extra routing may needed on local out, as the QUEUE target never
  * returns control to the table.
  */

 struct ip_rt_info {
 	__be32 daddr;
 	__be32 saddr;
 	u_int8_t tos;
 	u_int32_t mark;
 };

 static void nf_ip_saveroute(const struct sk_buff *skb,
 			    struct nf_queue_entry *entry)
 {
 	struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);

 	if (entry->hook == NF_INET_LOCAL_OUT) {
 		const struct iphdr *iph = ip_hdr(skb);

 		rt_info->tos = iph->tos;
 		rt_info->daddr = iph->daddr;
 		rt_info->saddr = iph->saddr;
 		rt_info->mark = skb->mark;
 	}
 }

 static int nf_ip_reroute(struct sk_buff *skb,
 			 const struct nf_queue_entry *entry)
 {
 	const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);

 	if (entry->hook == NF_INET_LOCAL_OUT) {
 		const struct iphdr *iph = ip_hdr(skb);

 		if (!(iph->tos == rt_info->tos &&
 		      skb->mark == rt_info->mark &&
 		      iph->daddr == rt_info->daddr &&
 		      iph->saddr == rt_info->saddr))
 			return ip_route_me_harder(skb, RTN_UNSPEC);
 	}
 	return 0;
 }

 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
 			    unsigned int dataoff, u_int8_t protocol)
 {
 	const struct iphdr *iph = ip_hdr(skb);
 	__sum16 csum = 0;

 	switch (skb->ip_summed) {
 	case CHECKSUM_COMPLETE:
 		if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 			break;
 		if ((protocol == 0 && !csum_fold(skb->csum)) ||
 		    !csum_tcpudp_magic(iph->saddr, iph->daddr,
 				       skb->len - dataoff, protocol,
 				       skb->csum)) {
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 			break;
 		}
 		/* fall through */
 	case CHECKSUM_NONE:
 		if (protocol == 0)
 			skb->csum = 0;
 		else
 			skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
 						       skb->len - dataoff,
 						       protocol, 0);
 		csum = __skb_checksum_complete(skb);
 	}
 	return csum;
 }
 EXPORT_SYMBOL(nf_ip_checksum);

 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
 				      unsigned int dataoff, unsigned int len,
 				      u_int8_t protocol)
 {
 	const struct iphdr *iph = ip_hdr(skb);
 	__sum16 csum = 0;

 	switch (skb->ip_summed) {
 	case CHECKSUM_COMPLETE:
 		if (len == skb->len - dataoff)
 			return nf_ip_checksum(skb, hook, dataoff, protocol);
 		/* fall through */
 	case CHECKSUM_NONE:
 		skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
 					       skb->len - dataoff, 0);
 		skb->ip_summed = CHECKSUM_NONE;
 		csum = __skb_checksum_complete_head(skb, dataoff + len);
 		if (!csum)
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
 	return csum;
 }

 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl)
 {
 	return ip_route_output_key(&init_net, (struct rtable **)dst, fl);
 }

 static const struct nf_afinfo nf_ip_afinfo = {
 	.family			= AF_INET,
 	.checksum		= nf_ip_checksum,
 	.checksum_partial	= nf_ip_checksum_partial,
 	.route			= nf_ip_route,
 	.saveroute		= nf_ip_saveroute,
 	.reroute		= nf_ip_reroute,
 	.route_key_size		= sizeof(struct ip_rt_info),
 };

 static int ipv4_netfilter_init(void)
 {
 	return nf_register_afinfo(&nf_ip_afinfo);
 }

 static void ipv4_netfilter_fini(void)
 {
 	nf_unregister_afinfo(&nf_ip_afinfo);
 }

 module_init(ipv4_netfilter_init);
 module_exit(ipv4_netfilter_fini);

 #ifdef CONFIG_SYSCTL
 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
 	{ .procname = "net", },
 	{ .procname = "ipv4", },
 	{ .procname = "netfilter", },
 	{ }
 };
 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
 #endif /* CONFIG_SYSCTL */
	/* IPv4 specific functions of netfilter core */
	#include <linux/kernel.h>
	#include <linux/netfilter.h>
	#include <linux/netfilter_ipv4.h>
	#include <linux/ip.h>
	#include <linux/skbuff.h>
	#include <linux/gfp.h>
	#include <net/route.h>
	#include <net/xfrm.h>
	#include <net/ip.h>
	#include <net/netfilter/nf_queue.h>

	/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
	int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
	{
	struct net *net = dev_net(skb_dst(skb)->dev);
	const struct iphdr *iph = ip_hdr(skb);
	struct rtable *rt;
	struct flowi fl = {};
	unsigned long orefdst;
	unsigned int hh_len;
	unsigned int type;

	type = inet_addr_type(net, iph->saddr);
	if (skb->sk && inet_sk(skb->sk)->transparent)
	type = RTN_LOCAL;
	if (addr_type == RTN_UNSPEC)
	addr_type = type;

	/* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
	* packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
	*/
	if (addr_type == RTN_LOCAL) {
	fl.nl_u.ip4_u.daddr = iph->daddr;
	if (type == RTN_LOCAL)
	fl.nl_u.ip4_u.saddr = iph->saddr;
	fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
	fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
	fl.mark = skb->mark;
	fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
	if (ip_route_output_key(net, &rt, &fl) != 0)
	return -1;

	/* Drop old route. */
	skb_dst_drop(skb);
	skb_dst_set(skb, &rt->u.dst);
	} else {
	/* non-local src, find valid iif to satisfy
	* rp-filter when calling ip_route_input. */
	fl.nl_u.ip4_u.daddr = iph->saddr;
	if (ip_route_output_key(net, &rt, &fl) != 0)
	return -1;

	orefdst = skb->_skb_refdst;
	if (ip_route_input(skb, iph->daddr, iph->saddr,
	RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
	dst_release(&rt->u.dst);
	return -1;
	}
	dst_release(&rt->u.dst);
	refdst_drop(orefdst);
	}

	if (skb_dst(skb)->error)
	return -1;

	#ifdef CONFIG_XFRM
	if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
	xfrm_decode_session(skb, &fl, AF_INET) == 0) {
	struct dst_entry *dst = skb_dst(skb);
	skb_dst_set(skb, NULL);
	if (xfrm_lookup(net, &dst, &fl, skb->sk, 0))
	return -1;
	skb_dst_set(skb, dst);
	}
	#endif

	/* Change in oif may mean change in hh_len. */
	hh_len = skb_dst(skb)->dev->hard_header_len;
	if (skb_headroom(skb) < hh_len &&
	pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
	return -1;

	return 0;
	}
	EXPORT_SYMBOL(ip_route_me_harder);

	#ifdef CONFIG_XFRM
	int ip_xfrm_me_harder(struct sk_buff *skb)
	{
	struct flowi fl;
	unsigned int hh_len;
	struct dst_entry *dst;

	if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
	return 0;
	if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
	return -1;

	dst = skb_dst(skb);
	if (dst->xfrm)
	dst = ((struct xfrm_dst *)dst)->route;
	dst_hold(dst);

	if (xfrm_lookup(dev_net(dst->dev), &dst, &fl, skb->sk, 0) < 0)
	return -1;

	skb_dst_drop(skb);
	skb_dst_set(skb, dst);

	/* Change in oif may mean change in hh_len. */
	hh_len = skb_dst(skb)->dev->hard_header_len;
	if (skb_headroom(skb) < hh_len &&
	pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
	return -1;
	return 0;
	}
	EXPORT_SYMBOL(ip_xfrm_me_harder);
	#endif

	void (ip_nat_decode_session)(struct sk_buff , struct flowi *);
	EXPORT_SYMBOL(ip_nat_decode_session);

	/*
	* Extra routing may needed on local out, as the QUEUE target never
	* returns control to the table.
	*/

	struct ip_rt_info {
	__be32 daddr;
	__be32 saddr;
	u_int8_t tos;
	u_int32_t mark;
	};

	static void nf_ip_saveroute(const struct sk_buff *skb,
	struct nf_queue_entry *entry)
	{
	struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);

	if (entry->hook == NF_INET_LOCAL_OUT) {
	const struct iphdr *iph = ip_hdr(skb);

	rt_info->tos = iph->tos;
	rt_info->daddr = iph->daddr;
	rt_info->saddr = iph->saddr;
	rt_info->mark = skb->mark;
	}
	}

	static int nf_ip_reroute(struct sk_buff *skb,
	const struct nf_queue_entry *entry)
	{
	const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);

	if (entry->hook == NF_INET_LOCAL_OUT) {
	const struct iphdr *iph = ip_hdr(skb);

	if (!(iph->tos == rt_info->tos &&
	skb->mark == rt_info->mark &&
	iph->daddr == rt_info->daddr &&
	iph->saddr == rt_info->saddr))
	return ip_route_me_harder(skb, RTN_UNSPEC);
	}
	return 0;
	}

	__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
	unsigned int dataoff, u_int8_t protocol)
	{
	const struct iphdr *iph = ip_hdr(skb);
	__sum16 csum = 0;

	switch (skb->ip_summed) {
	case CHECKSUM_COMPLETE:
	if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
	break;
	if ((protocol == 0 && !csum_fold(skb->csum)) \|\|
	!csum_tcpudp_magic(iph->saddr, iph->daddr,
	skb->len - dataoff, protocol,
	skb->csum)) {
	skb->ip_summed = CHECKSUM_UNNECESSARY;
	break;
	}
	/* fall through */
	case CHECKSUM_NONE:
	if (protocol == 0)
	skb->csum = 0;
	else
	skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
	skb->len - dataoff,
	protocol, 0);
	csum = __skb_checksum_complete(skb);
	}
	return csum;
	}
	EXPORT_SYMBOL(nf_ip_checksum);

	static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
	unsigned int dataoff, unsigned int len,
	u_int8_t protocol)
	{
	const struct iphdr *iph = ip_hdr(skb);
	__sum16 csum = 0;

	switch (skb->ip_summed) {
	case CHECKSUM_COMPLETE:
	if (len == skb->len - dataoff)
	return nf_ip_checksum(skb, hook, dataoff, protocol);
	/* fall through */
	case CHECKSUM_NONE:
	skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
	skb->len - dataoff, 0);
	skb->ip_summed = CHECKSUM_NONE;
	csum = __skb_checksum_complete_head(skb, dataoff + len);
	if (!csum)
	skb->ip_summed = CHECKSUM_UNNECESSARY;
	}
	return csum;
	}

	static int nf_ip_route(struct dst_entry *dst, struct flowi fl)
	{
	return ip_route_output_key(&init_net, (struct rtable **)dst, fl);
	}

	static const struct nf_afinfo nf_ip_afinfo = {
	.family = AF_INET,
	.checksum = nf_ip_checksum,
	.checksum_partial = nf_ip_checksum_partial,
	.route = nf_ip_route,
	.saveroute = nf_ip_saveroute,
	.reroute = nf_ip_reroute,
	.route_key_size = sizeof(struct ip_rt_info),
	};

	static int ipv4_netfilter_init(void)
	{
	return nf_register_afinfo(&nf_ip_afinfo);
	}

	static void ipv4_netfilter_fini(void)
	{
	nf_unregister_afinfo(&nf_ip_afinfo);
	}

	module_init(ipv4_netfilter_init);
	module_exit(ipv4_netfilter_fini);

	#ifdef CONFIG_SYSCTL
	struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
	{ .procname = "net", },
	{ .procname = "ipv4", },
	{ .procname = "netfilter", },
	{ }
	};
	EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
	#endif /* CONFIG_SYSCTL */