/* * IPv4 specific functions of netfilter core * * Rusty Russell (C) 2000 -- This code is GPL. * Patrick McHardy (C) 2006-2012 */#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 <linux/export.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 int addr_type){	struct net *net = dev_net(skb_dst(skb)->dev);	const struct iphdr *iph = ip_hdr(skb);	struct rtable *rt;	struct flowi4 fl4 = {};	__be32 saddr = iph->saddr;	__u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;	unsigned int hh_len; 	if (addr_type == RTN_UNSPEC)		addr_type = inet_addr_type(net, saddr);	if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)		flags |= FLOWI_FLAG_ANYSRC;	else		saddr = 0; 	/* 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.	 */	fl4.daddr = iph->daddr;	fl4.saddr = saddr;	fl4.flowi4_tos = RT_TOS(iph->tos);	fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;	fl4.flowi4_mark = skb->mark;	fl4.flowi4_flags = flags;	rt = ip_route_output_key(net, &fl4);	if (IS_ERR(rt))		return PTR_ERR(rt); 	/* Drop old route. */	skb_dst_drop(skb);	skb_dst_set(skb, &rt->dst); 	if (skb_dst(skb)->error)		return skb_dst(skb)->error; #ifdef CONFIG_XFRM	if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&	    xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {		struct dst_entry *dst = skb_dst(skb);		skb_dst_set(skb, NULL);		dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);		if (IS_ERR(dst))			return PTR_ERR(dst);;		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_DATA_ALIGN(hh_len - skb_headroom(skb)),				0, GFP_ATOMIC))		return -ENOMEM; 	return 0;}EXPORT_SYMBOL(ip_route_me_harder); /* * 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;		return __skb_checksum_complete_head(skb, dataoff + len);	}	return csum;} static int nf_ip_route(struct net *net, struct dst_entry **dst,		       struct flowi *fl, bool strict __always_unused){	struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);	if (IS_ERR(rt))		return PTR_ERR(rt);	*dst = &rt->dst;	return 0;} 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 __init ipv4_netfilter_init(void){	return nf_register_afinfo(&nf_ip_afinfo);} static void __exit ipv4_netfilter_fini(void){	nf_unregister_afinfo(&nf_ip_afinfo);} module_init(ipv4_netfilter_init);module_exit(ipv4_netfilter_fini);