ARK-OS/arkos/kernel/include/net/ip.h

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Definitions for the IP module.
 *
 * Version:	@(#)ip.h	1.0.2	05/07/93
 *
 * Authors:	Ross Biro
 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *
 * Changes:
 *		Mike McLagan    :       Routing by source
 */
#ifndef _IP_H
#define _IP_H

#include <linux/types.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/skbuff.h>
#include <linux/jhash.h>
#include <linux/sockptr.h>
#include <linux/static_key.h>

#include <net/inet_sock.h>
#include <net/route.h>
#include <net/snmp.h>
#include <net/flow.h>
#include <net/flow_dissector.h>
#include <net/netns/hash.h>
#include <net/lwtunnel.h>
#include <net/inet_dscp.h>

#define IPV4_MAX_PMTU		65535U		/* RFC 2675, Section 5.1 */
#define IPV4_MIN_MTU		68			/* RFC 791 */

extern unsigned int sysctl_fib_sync_mem;
extern unsigned int sysctl_fib_sync_mem_min;
extern unsigned int sysctl_fib_sync_mem_max;

struct sock;

struct inet_skb_parm {
	int			iif;
	struct ip_options	opt;		/* Compiled IP options		*/
	u16			flags;

#define IPSKB_FORWARDED		BIT(0)
#define IPSKB_XFRM_TUNNEL_SIZE	BIT(1)
#define IPSKB_XFRM_TRANSFORMED	BIT(2)
#define IPSKB_FRAG_COMPLETE	BIT(3)
#define IPSKB_REROUTED		BIT(4)
#define IPSKB_DOREDIRECT	BIT(5)
#define IPSKB_FRAG_PMTU		BIT(6)
#define IPSKB_L3SLAVE		BIT(7)
#define IPSKB_NOPOLICY		BIT(8)
#define IPSKB_MULTIPATH		BIT(9)
#define IPSKB_MCROUTE		BIT(10)

	u16			frag_max_size;
};

static inline bool ipv4_l3mdev_skb(u16 flags)
{
	return !!(flags & IPSKB_L3SLAVE);
}

static inline unsigned int ip_hdrlen(const struct sk_buff *skb)
{
	return ip_hdr(skb)->ihl * 4;
}

struct ipcm_cookie {
	struct sockcm_cookie	sockc;
	__be32			addr;
	int			oif;
	struct ip_options_rcu	*opt;
	__u8			protocol;
	__u8			ttl;
	__s16			tos;
	__u16			gso_size;
};

static inline void ipcm_init(struct ipcm_cookie *ipcm)
{
	*ipcm = (struct ipcm_cookie) { .tos = -1 };
}

static inline void ipcm_init_sk(struct ipcm_cookie *ipcm,
				const struct inet_sock *inet)
{
	*ipcm = (struct ipcm_cookie) {
		.tos = READ_ONCE(inet->tos),
	};

	sockcm_init(&ipcm->sockc, &inet->sk);

	ipcm->oif = READ_ONCE(inet->sk.sk_bound_dev_if);
	ipcm->addr = inet->inet_saddr;
	ipcm->protocol = READ_ONCE(inet->inet_num);
}

#define IPCB(skb) ((struct inet_skb_parm*)((skb)->cb))
#define PKTINFO_SKB_CB(skb) ((struct in_pktinfo *)((skb)->cb))

/* return enslaved device index if relevant */
static inline int inet_sdif(const struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
	if (skb && ipv4_l3mdev_skb(IPCB(skb)->flags))
		return IPCB(skb)->iif;
#endif
	return 0;
}

/* Special input handler for packets caught by router alert option.
   They are selected only by protocol field, and then processed likely
   local ones; but only if someone wants them! Otherwise, router
   not running rsvpd will kill RSVP.

   It is user level problem, what it will make with them.
   I have no idea, how it will masquearde or NAT them (it is joke, joke :-)),
   but receiver should be enough clever f.e. to forward mtrace requests,
   sent to multicast group to reach destination designated router.
 */

struct ip_ra_chain {
	struct ip_ra_chain __rcu *next;
	struct sock		*sk;
	union {
		void			(*destructor)(struct sock *);
		struct sock		*saved_sk;
	};
	struct rcu_head		rcu;
};

/* IP flags. */
#define IP_CE		0x8000		/* Flag: "Congestion"		*/
#define IP_DF		0x4000		/* Flag: "Don't Fragment"	*/
#define IP_MF		0x2000		/* Flag: "More Fragments"	*/
#define IP_OFFSET	0x1FFF		/* "Fragment Offset" part	*/

#define IP_FRAG_TIME	(30 * HZ)		/* fragment lifetime	*/

struct msghdr;
struct net_device;
struct packet_type;
struct rtable;
struct sockaddr;

int igmp_mc_init(void);

/*
 *	Functions provided by ip.c
 */

int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
			  __be32 saddr, __be32 daddr,
			  struct ip_options_rcu *opt, u8 tos);
int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
	   struct net_device *orig_dev);
void ip_list_rcv(struct list_head *head, struct packet_type *pt,
		 struct net_device *orig_dev);
int ip_local_deliver(struct sk_buff *skb);
void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int proto);
int ip_mr_input(struct sk_buff *skb);
int ip_mr_output(struct net *net, struct sock *sk, struct sk_buff *skb);
int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb);
int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb);
int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
		   int (*output)(struct net *, struct sock *, struct sk_buff *));

struct ip_fraglist_iter {
	struct sk_buff	*frag;
	struct iphdr	*iph;
	int		offset;
	unsigned int	hlen;
};

void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
		      unsigned int hlen, struct ip_fraglist_iter *iter);
void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter);

static inline struct sk_buff *ip_fraglist_next(struct ip_fraglist_iter *iter)
{
	struct sk_buff *skb = iter->frag;

	iter->frag = skb->next;
	skb_mark_not_on_list(skb);

	return skb;
}

struct ip_frag_state {
	bool		DF;
	unsigned int	hlen;
	unsigned int	ll_rs;
	unsigned int	mtu;
	unsigned int	left;
	int		offset;
	int		ptr;
	__be16		not_last_frag;
};

void ip_frag_init(struct sk_buff *skb, unsigned int hlen, unsigned int ll_rs,
		  unsigned int mtu, bool DF, struct ip_frag_state *state);
struct sk_buff *ip_frag_next(struct sk_buff *skb,
			     struct ip_frag_state *state);

void ip_send_check(struct iphdr *ip);
int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb);
int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb);

int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
		    __u8 tos);
void ip_init(void);
int ip_append_data(struct sock *sk, struct flowi4 *fl4,
		   int getfrag(void *from, char *to, int offset, int len,
			       int odd, struct sk_buff *skb),
		   void *from, int len, int protolen,
		   struct ipcm_cookie *ipc,
		   struct rtable **rt,
		   unsigned int flags);
int ip_generic_getfrag(void *from, char *to, int offset, int len, int odd,
		       struct sk_buff *skb);
struct sk_buff *__ip_make_skb(struct sock *sk, struct flowi4 *fl4,
			      struct sk_buff_head *queue,
			      struct inet_cork *cork);
int ip_send_skb(struct net *net, struct sk_buff *skb);
int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4);
void ip_flush_pending_frames(struct sock *sk);
struct sk_buff *ip_make_skb(struct sock *sk, struct flowi4 *fl4,
			    int getfrag(void *from, char *to, int offset,
					int len, int odd, struct sk_buff *skb),
			    void *from, int length, int transhdrlen,
			    struct ipcm_cookie *ipc, struct rtable **rtp,
			    struct inet_cork *cork, unsigned int flags);

int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl);

static inline struct sk_buff *ip_finish_skb(struct sock *sk, struct flowi4 *fl4)
{
	return __ip_make_skb(sk, fl4, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
}

/* Get the route scope that should be used when sending a packet. */
static inline u8 ip_sendmsg_scope(const struct inet_sock *inet,
				  const struct ipcm_cookie *ipc,
				  const struct msghdr *msg)
{
	if (sock_flag(&inet->sk, SOCK_LOCALROUTE) ||
	    msg->msg_flags & MSG_DONTROUTE ||
	    (ipc->opt && ipc->opt->opt.is_strictroute))
		return RT_SCOPE_LINK;

	return RT_SCOPE_UNIVERSE;
}

/* datagram.c */
int __ip4_datagram_connect(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len);
int ip4_datagram_connect(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len);

void ip4_datagram_release_cb(struct sock *sk);

struct ip_reply_arg {
	struct kvec iov[1];
	int	    flags;
	__wsum 	    csum;
	int	    csumoffset; /* u16 offset of csum in iov[0].iov_base */
				/* -1 if not needed */
	int	    bound_dev_if;
	u8  	    tos;
	kuid_t	    uid;
};

#define IP_REPLY_ARG_NOSRCCHECK 1

static inline __u8 ip_reply_arg_flowi_flags(const struct ip_reply_arg *arg)
{
	return (arg->flags & IP_REPLY_ARG_NOSRCCHECK) ? FLOWI_FLAG_ANYSRC : 0;
}

void ip_send_unicast_reply(struct sock *sk, const struct sock *orig_sk,
			   struct sk_buff *skb,
			   const struct ip_options *sopt,
			   __be32 daddr, __be32 saddr,
			   const struct ip_reply_arg *arg,
			   unsigned int len, u64 transmit_time, u32 txhash);

#define IP_INC_STATS(net, field)	SNMP_INC_STATS64((net)->mib.ip_statistics, field)
#define __IP_INC_STATS(net, field)	__SNMP_INC_STATS64((net)->mib.ip_statistics, field)
#define IP_ADD_STATS(net, field, val)	SNMP_ADD_STATS64((net)->mib.ip_statistics, field, val)
#define __IP_ADD_STATS(net, field, val) __SNMP_ADD_STATS64((net)->mib.ip_statistics, field, val)
#define IP_UPD_PO_STATS(net, field, val) SNMP_UPD_PO_STATS64((net)->mib.ip_statistics, field, val)
#define __IP_UPD_PO_STATS(net, field, val) __SNMP_UPD_PO_STATS64((net)->mib.ip_statistics, field, val)
#define NET_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.net_statistics, field)
#define __NET_INC_STATS(net, field)	__SNMP_INC_STATS((net)->mib.net_statistics, field)
#define NET_ADD_STATS(net, field, adnd)	SNMP_ADD_STATS((net)->mib.net_statistics, field, adnd)
#define __NET_ADD_STATS(net, field, adnd) __SNMP_ADD_STATS((net)->mib.net_statistics, field, adnd)

static inline u64 snmp_get_cpu_field(void __percpu *mib, int cpu, int offt)
{
	return  *(((unsigned long *)per_cpu_ptr(mib, cpu)) + offt);
}

unsigned long snmp_fold_field(void __percpu *mib, int offt);
#if BITS_PER_LONG==32
u64 snmp_get_cpu_field64(void __percpu *mib, int cpu, int offct,
			 size_t syncp_offset);
u64 snmp_fold_field64(void __percpu *mib, int offt, size_t sync_off);
#else
static inline u64  snmp_get_cpu_field64(void __percpu *mib, int cpu, int offct,
					size_t syncp_offset)
{
	return snmp_get_cpu_field(mib, cpu, offct);

}

static inline u64 snmp_fold_field64(void __percpu *mib, int offt, size_t syncp_off)
{
	return snmp_fold_field(mib, offt);
}
#endif

#define snmp_get_cpu_field64_batch_cnt(buff64, stats_list, cnt,	\
				       mib_statistic, offset)	\
{ \
	int i, c; \
	for_each_possible_cpu(c) { \
		for (i = 0; i < cnt; i++) \
			buff64[i] += snmp_get_cpu_field64( \
					mib_statistic, \
					c, stats_list[i].entry, \
					offset); \
	} \
}

#define snmp_get_cpu_field_batch_cnt(buff, stats_list, cnt, mib_statistic) \
{ \
	int i, c; \
	for_each_possible_cpu(c) { \
		for (i = 0; i < cnt; i++) \
			buff[i] += snmp_get_cpu_field( \
						mib_statistic, \
						c, stats_list[i].entry); \
	} \
}

static inline void inet_get_local_port_range(const struct net *net, int *low, int *high)
{
	u32 range = READ_ONCE(net->ipv4.ip_local_ports.range);

	*low = range & 0xffff;
	*high = range >> 16;
}
bool inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high);

#ifdef CONFIG_SYSCTL
static inline bool inet_is_local_reserved_port(const struct net *net, unsigned short port)
{
	if (!net->ipv4.sysctl_local_reserved_ports)
		return false;
	return test_bit(port, net->ipv4.sysctl_local_reserved_ports);
}

static inline bool sysctl_dev_name_is_allowed(const char *name)
{
	return strcmp(name, "default") != 0  && strcmp(name, "all") != 0;
}

static inline bool inet_port_requires_bind_service(struct net *net, unsigned short port)
{
	return port < READ_ONCE(net->ipv4.sysctl_ip_prot_sock);
}

#else
static inline bool inet_is_local_reserved_port(struct net *net, unsigned short port)
{
	return false;
}

static inline bool inet_port_requires_bind_service(struct net *net, unsigned short port)
{
	return port < PROT_SOCK;
}
#endif

__be32 inet_current_timestamp(void);

/* From inetpeer.c */
extern int inet_peer_threshold;
extern int inet_peer_minttl;
extern int inet_peer_maxttl;

void ipfrag_init(void);

void ip_static_sysctl_init(void);

#define IP4_REPLY_MARK(net, mark) \
	(READ_ONCE((net)->ipv4.sysctl_fwmark_reflect) ? (mark) : 0)

static inline bool ip_is_fragment(const struct iphdr *iph)
{
	return (iph->frag_off & htons(IP_MF | IP_OFFSET)) != 0;
}

#ifdef CONFIG_INET
#include <net/dst.h>

/* The function in 2.2 was invalid, producing wrong result for
 * check=0xFEFF. It was noticed by Arthur Skawina _year_ ago. --ANK(000625) */
static inline
int ip_decrease_ttl(struct iphdr *iph)
{
	u32 check = (__force u32)iph->check;
	check += (__force u32)htons(0x0100);
	iph->check = (__force __sum16)(check + (check>=0xFFFF));
	return --iph->ttl;
}

static inline dscp_t ip4h_dscp(const struct iphdr *ip4h)
{
	return inet_dsfield_to_dscp(ip4h->tos);
}

static inline int ip_mtu_locked(const struct dst_entry *dst)
{
	const struct rtable *rt = dst_rtable(dst);

	return rt->rt_mtu_locked || dst_metric_locked(dst, RTAX_MTU);
}

static inline
int ip_dont_fragment(const struct sock *sk, const struct dst_entry *dst)
{
	u8 pmtudisc = READ_ONCE(inet_sk(sk)->pmtudisc);

	return  pmtudisc == IP_PMTUDISC_DO ||
		(pmtudisc == IP_PMTUDISC_WANT &&
		 !ip_mtu_locked(dst));
}

static inline bool ip_sk_accept_pmtu(const struct sock *sk)
{
	u8 pmtudisc = READ_ONCE(inet_sk(sk)->pmtudisc);

	return pmtudisc != IP_PMTUDISC_INTERFACE &&
	       pmtudisc != IP_PMTUDISC_OMIT;
}

static inline bool ip_sk_use_pmtu(const struct sock *sk)
{
	return READ_ONCE(inet_sk(sk)->pmtudisc) < IP_PMTUDISC_PROBE;
}

static inline bool ip_sk_ignore_df(const struct sock *sk)
{
	u8 pmtudisc = READ_ONCE(inet_sk(sk)->pmtudisc);

	return pmtudisc < IP_PMTUDISC_DO || pmtudisc == IP_PMTUDISC_OMIT;
}

static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
						    bool forwarding)
{
	const struct rtable *rt = dst_rtable(dst);
	const struct net_device *dev;
	unsigned int mtu, res;
	struct net *net;

	rcu_read_lock();

	dev = dst_dev_rcu(dst);
	net = dev_net_rcu(dev);
	if (READ_ONCE(net->ipv4.sysctl_ip_fwd_use_pmtu) ||
	    ip_mtu_locked(dst) ||
	    !forwarding) {
		mtu = rt->rt_pmtu;
		if (mtu && time_before(jiffies, READ_ONCE(rt->dst.expires)))
			goto out;
	}

	/* 'forwarding = true' case should always honour route mtu */
	mtu = dst_metric_raw(dst, RTAX_MTU);
	if (mtu)
		goto out;

	mtu = READ_ONCE(dev->mtu);

	if (unlikely(ip_mtu_locked(dst))) {
		if (rt->rt_uses_gateway && mtu > 576)
			mtu = 576;
	}

out:
	mtu = min_t(unsigned int, mtu, IP_MAX_MTU);

	res = mtu - lwtunnel_headroom(dst->lwtstate, mtu);

	rcu_read_unlock();

	return res;
}

static inline unsigned int ip_skb_dst_mtu(struct sock *sk,
					  const struct sk_buff *skb)
{
	const struct dst_entry *dst = skb_dst(skb);
	unsigned int mtu;

	if (!sk || !sk_fullsock(sk) || ip_sk_use_pmtu(sk)) {
		bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;

		return ip_dst_mtu_maybe_forward(dst, forwarding);
	}

	mtu = min(READ_ONCE(dst_dev(dst)->mtu), IP_MAX_MTU);
	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
}

struct dst_metrics *ip_fib_metrics_init(struct nlattr *fc_mx, int fc_mx_len,
					struct netlink_ext_ack *extack);
static inline void ip_fib_metrics_put(struct dst_metrics *fib_metrics)
{
	if (fib_metrics != &dst_default_metrics &&
	    refcount_dec_and_test(&fib_metrics->refcnt))
		kfree(fib_metrics);
}

/* ipv4 and ipv6 both use refcounted metrics if it is not the default */
static inline
void ip_dst_init_metrics(struct dst_entry *dst, struct dst_metrics *fib_metrics)
{
	dst_init_metrics(dst, fib_metrics->metrics, true);

	if (fib_metrics != &dst_default_metrics) {
		dst->_metrics |= DST_METRICS_REFCOUNTED;
		refcount_inc(&fib_metrics->refcnt);
	}
}

static inline
void ip_dst_metrics_put(struct dst_entry *dst)
{
	struct dst_metrics *p = (struct dst_metrics *)DST_METRICS_PTR(dst);

	if (p != &dst_default_metrics && refcount_dec_and_test(&p->refcnt))
		kfree(p);
}

void __ip_select_ident(struct net *net, struct iphdr *iph, int segs);

static inline void ip_select_ident_segs(struct net *net, struct sk_buff *skb,
					struct sock *sk, int segs)
{
	struct iphdr *iph = ip_hdr(skb);

	/* We had many attacks based on IPID, use the private
	 * generator as much as we can.
	 */
	if (sk && inet_sk(sk)->inet_daddr) {
		int val;

		/* avoid atomic operations for TCP,
		 * as we hold socket lock at this point.
		 */
		if (sk_is_tcp(sk)) {
			sock_owned_by_me(sk);
			val = atomic_read(&inet_sk(sk)->inet_id);
			atomic_set(&inet_sk(sk)->inet_id, val + segs);
		} else {
			val = atomic_add_return(segs, &inet_sk(sk)->inet_id);
		}
		iph->id = htons(val);
		return;
	}
	if ((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) {
		iph->id = 0;
	} else {
		/* Unfortunately we need the big hammer to get a suitable IPID */
		__ip_select_ident(net, iph, segs);
	}
}

static inline void ip_select_ident(struct net *net, struct sk_buff *skb,
				   struct sock *sk)
{
	ip_select_ident_segs(net, skb, sk, 1);
}

static inline __wsum inet_compute_pseudo(struct sk_buff *skb, int proto)
{
	return csum_tcpudp_nofold(ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
				  skb->len, proto, 0);
}

/* copy IPv4 saddr & daddr to flow_keys, possibly using 64bit load/store
 * Equivalent to :	flow->v4addrs.src = iph->saddr;
 *			flow->v4addrs.dst = iph->daddr;
 */
static inline void iph_to_flow_copy_v4addrs(struct flow_keys *flow,
					    const struct iphdr *iph)
{
	BUILD_BUG_ON(offsetof(typeof(flow->addrs), v4addrs.dst) !=
		     offsetof(typeof(flow->addrs), v4addrs.src) +
			      sizeof(flow->addrs.v4addrs.src));
	memcpy(&flow->addrs.v4addrs, &iph->addrs, sizeof(flow->addrs.v4addrs));
	flow->control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
}

/*
 *	Map a multicast IP onto multicast MAC for type ethernet.
 */

static inline void ip_eth_mc_map(__be32 naddr, char *buf)
{
	__u32 addr=ntohl(naddr);
	buf[0]=0x01;
	buf[1]=0x00;
	buf[2]=0x5e;
	buf[5]=addr&0xFF;
	addr>>=8;
	buf[4]=addr&0xFF;
	addr>>=8;
	buf[3]=addr&0x7F;
}

/*
 *	Map a multicast IP onto multicast MAC for type IP-over-InfiniBand.
 *	Leave P_Key as 0 to be filled in by driver.
 */

static inline void ip_ib_mc_map(__be32 naddr, const unsigned char *broadcast, char *buf)
{
	__u32 addr;
	unsigned char scope = broadcast[5] & 0xF;

	buf[0]  = 0;		/* Reserved */
	buf[1]  = 0xff;		/* Multicast QPN */
	buf[2]  = 0xff;
	buf[3]  = 0xff;
	addr    = ntohl(naddr);
	buf[4]  = 0xff;
	buf[5]  = 0x10 | scope;	/* scope from broadcast address */
	buf[6]  = 0x40;		/* IPv4 signature */
	buf[7]  = 0x1b;
	buf[8]  = broadcast[8];		/* P_Key */
	buf[9]  = broadcast[9];
	buf[10] = 0;
	buf[11] = 0;
	buf[12] = 0;
	buf[13] = 0;
	buf[14] = 0;
	buf[15] = 0;
	buf[19] = addr & 0xff;
	addr  >>= 8;
	buf[18] = addr & 0xff;
	addr  >>= 8;
	buf[17] = addr & 0xff;
	addr  >>= 8;
	buf[16] = addr & 0x0f;
}

static inline void ip_ipgre_mc_map(__be32 naddr, const unsigned char *broadcast, char *buf)
{
	if ((broadcast[0] | broadcast[1] | broadcast[2] | broadcast[3]) != 0)
		memcpy(buf, broadcast, 4);
	else
		memcpy(buf, &naddr, sizeof(naddr));
}

#if IS_ENABLED(CONFIG_IPV6)
#include <linux/ipv6.h>
#endif

static __inline__ void inet_reset_saddr(struct sock *sk)
{
	inet_sk(sk)->inet_rcv_saddr = inet_sk(sk)->inet_saddr = 0;
#if IS_ENABLED(CONFIG_IPV6)
	if (sk->sk_family == PF_INET6) {
		struct ipv6_pinfo *np = inet6_sk(sk);

		memset(&np->saddr, 0, sizeof(np->saddr));
		memset(&sk->sk_v6_rcv_saddr, 0, sizeof(sk->sk_v6_rcv_saddr));
	}
#endif
}

#endif

#if IS_MODULE(CONFIG_IPV6)
#define EXPORT_IPV6_MOD(X) EXPORT_SYMBOL(X)
#define EXPORT_IPV6_MOD_GPL(X) EXPORT_SYMBOL_GPL(X)
#else
#define EXPORT_IPV6_MOD(X)
#define EXPORT_IPV6_MOD_GPL(X)
#endif

static inline unsigned int ipv4_addr_hash(__be32 ip)
{
	return (__force unsigned int) ip;
}

static inline u32 __ipv4_addr_hash(const __be32 ip, const u32 initval)
{
	return jhash_1word((__force u32)ip, initval);
}

static inline u32 ipv4_portaddr_hash(const struct net *net,
				     __be32 saddr,
				     unsigned int port)
{
	return jhash_1word((__force u32)saddr, net_hash_mix(net)) ^ port;
}

bool ip_call_ra_chain(struct sk_buff *skb);

/*
 *	Functions provided by ip_fragment.c
 */

enum ip_defrag_users {
	IP_DEFRAG_LOCAL_DELIVER,
	IP_DEFRAG_CALL_RA_CHAIN,
	IP_DEFRAG_CONNTRACK_IN,
	__IP_DEFRAG_CONNTRACK_IN_END	= IP_DEFRAG_CONNTRACK_IN + USHRT_MAX,
	IP_DEFRAG_CONNTRACK_OUT,
	__IP_DEFRAG_CONNTRACK_OUT_END	= IP_DEFRAG_CONNTRACK_OUT + USHRT_MAX,
	IP_DEFRAG_CONNTRACK_BRIDGE_IN,
	__IP_DEFRAG_CONNTRACK_BRIDGE_IN = IP_DEFRAG_CONNTRACK_BRIDGE_IN + USHRT_MAX,
	IP_DEFRAG_VS_IN,
	IP_DEFRAG_VS_OUT,
	IP_DEFRAG_VS_FWD,
	IP_DEFRAG_AF_PACKET,
	IP_DEFRAG_MACVLAN,
};

/* Return true if the value of 'user' is between 'lower_bond'
 * and 'upper_bond' inclusively.
 */
static inline bool ip_defrag_user_in_between(u32 user,
					     enum ip_defrag_users lower_bond,
					     enum ip_defrag_users upper_bond)
{
	return user >= lower_bond && user <= upper_bond;
}

int ip_defrag(struct net *net, struct sk_buff *skb, u32 user);
#ifdef CONFIG_INET
struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user);
#else
static inline struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
{
	return skb;
}
#endif

/*
 *	Functions provided by ip_forward.c
 */

int ip_forward(struct sk_buff *skb);

/*
 *	Functions provided by ip_options.c
 */

void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
		      __be32 daddr, struct rtable *rt);

int __ip_options_echo(struct net *net, struct ip_options *dopt,
		      struct sk_buff *skb, const struct ip_options *sopt);
static inline int ip_options_echo(struct net *net, struct ip_options *dopt,
				  struct sk_buff *skb)
{
	return __ip_options_echo(net, dopt, skb, &IPCB(skb)->opt);
}

void ip_options_fragment(struct sk_buff *skb);
int __ip_options_compile(struct net *net, struct ip_options *opt,
			 struct sk_buff *skb, __be32 *info);
int ip_options_compile(struct net *net, struct ip_options *opt,
		       struct sk_buff *skb);
int ip_options_get(struct net *net, struct ip_options_rcu **optp,
		   sockptr_t data, int optlen);
void ip_options_undo(struct ip_options *opt);
void ip_forward_options(struct sk_buff *skb);
int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev);

/*
 *	Functions provided by ip_sockglue.c
 */

void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb, bool drop_dst);
void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
			 struct sk_buff *skb, int tlen, int offset);
int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
		 struct ipcm_cookie *ipc, bool allow_ipv6);
DECLARE_STATIC_KEY_FALSE(ip4_min_ttl);
int do_ip_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
		     unsigned int optlen);
int ip_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
		  unsigned int optlen);
int do_ip_getsockopt(struct sock *sk, int level, int optname,
		     sockptr_t optval, sockptr_t optlen);
int ip_getsockopt(struct sock *sk, int level, int optname, char __user *optval,
		  int __user *optlen);
int ip_ra_control(struct sock *sk, unsigned char on,
		  void (*destructor)(struct sock *));

int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len);
void ip_icmp_error(struct sock *sk, struct sk_buff *skb, int err, __be16 port,
		   u32 info, u8 *payload);
void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 dport,
		    u32 info);

static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
{
	ip_cmsg_recv_offset(msg, skb->sk, skb, 0, 0);
}

bool icmp_global_allow(struct net *net);
void icmp_global_consume(struct net *net);

#ifdef CONFIG_PROC_FS
int ip_misc_proc_init(void);
#endif

int rtm_getroute_parse_ip_proto(struct nlattr *attr, u8 *ip_proto, u8 family,
				struct netlink_ext_ack *extack);

static inline bool inetdev_valid_mtu(unsigned int mtu)
{
	return likely(mtu >= IPV4_MIN_MTU);
}

void ip_sock_set_freebind(struct sock *sk);
int ip_sock_set_mtu_discover(struct sock *sk, int val);
void ip_sock_set_pktinfo(struct sock *sk);
void ip_sock_set_recverr(struct sock *sk);
void ip_sock_set_tos(struct sock *sk, int val);
void  __ip_sock_set_tos(struct sock *sk, int val);

#endif	/* _IP_H */