ip.h

/*
 * 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
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */
#ifndef _IP_H
#define _IP_H

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

#include <net/inet_sock.h>
#include <net/snmp.h>
#include <net/flow.h>

struct sock;


//通过IPCB访问这个           信息控制块inet_skb_parm结构存储在这里面  IP层用IPCB访问该结构，主要存储一些选项以及IP处理过程中的标志
//这个是struct tcp_skb_cb的一部分，也就是说tcp_skb_cb包含IP选项以及TCP选项
//TCP接收过程中的TCP选项字段从接收的SKB中解析出来，见tcp_parse_options，最终TCP选项字段存放在inet_request_sock中,IP选项字段存储在skb->cb中
struct inet_skb_parm { //见樊东东P220       该结构中存用ip头部选项字段
	struct ip_options	opt;		/* Compiled IP options		*/
	unsigned char		flags; //flag取值为下面这几种

#define IPSKB_FORWARDED		1  
#define IPSKB_XFRM_TUNNEL_SIZE	2
#define IPSKB_XFRM_TRANSFORMED	4
#define IPSKB_FRAG_COMPLETE	8
#define IPSKB_REROUTED		16
};

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

/*
 * IP控制信息块由ipcm_cookie结构描述，
 * 存储有关输出的控制信息，包括
 * 发送UDP数据包的源地址、输出
 * 网络设备接口索引以及IP首部中
 * 的选项，在整个输出过程中起
 * 传递信息的作用。
 */ //UDP或者raw数据报相关
struct ipcm_cookie
{
	/*
	 * UDP数据包或RAW数据包的目的地址。
	 * 只有当存在IP选项时才设置，用作
	 * 源路由选项的最后一跳地址。
	 */
	__be32			addr;
	/*
	 * UDP数据包或RAW数据包的输出网络设备。
	 */
	int			oif;
	/*
	 * 如果不为NULL，则指向发送数据包的
	 * IP选项信息。
	 */
	struct ip_options	*opt;//数据报的IP选项信息，也就是IP头部中的扩展添加信息。
	union skb_shared_tx	shtx;
};


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

struct ip_ra_chain {
	struct ip_ra_chain	*next;
	struct sock		*sk;
	void			(*destructor)(struct sock *);
};

extern struct ip_ra_chain *ip_ra_chain;
extern rwlock_t ip_ra_lock;

/* 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;

extern int		igmp_mc_proc_init(void);

/*
 *	Functions provided by ip.c
 */

extern int		ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
					      __be32 saddr, __be32 daddr,
					      struct ip_options *opt);
extern int		ip_rcv(struct sk_buff *skb, struct net_device *dev,
			       struct packet_type *pt, struct net_device *orig_dev);
extern int		ip_local_deliver(struct sk_buff *skb);
extern int		ip_mr_input(struct sk_buff *skb);
extern int		ip_output(struct sk_buff *skb);
extern int		ip_mc_output(struct sk_buff *skb);
extern int		ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
extern int		ip_do_nat(struct sk_buff *skb);
extern void		ip_send_check(struct iphdr *ip);
extern int		__ip_local_out(struct sk_buff *skb);
extern int		ip_local_out(struct sk_buff *skb);
extern int		ip_queue_xmit(struct sk_buff *skb);
extern void		ip_init(void);
extern int		ip_append_data(struct sock *sk,
				       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);
extern int		ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb);
extern ssize_t		ip_append_page(struct sock *sk, struct page *page,
				int offset, size_t size, int flags);
extern int		ip_push_pending_frames(struct sock *sk);
extern void		ip_flush_pending_frames(struct sock *sk);

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

/*
 *	Map a multicast IP onto multicast MAC for type Token Ring.
 *      This conforms to RFC1469 Option 2 Multicasting i.e.
 *      using a functional address to transmit / receive 
 *      multicast packets.
 */

static inline void ip_tr_mc_map(__be32 addr, char *buf)
{
	buf[0]=0xC0;
	buf[1]=0x00;
	buf[2]=0x00;
	buf[3]=0x04;
	buf[4]=0x00;
	buf[5]=0x00;
}

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;
}; 

#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_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
		   unsigned int len); 

struct ipv4_config {
	int	log_martians;
	int	no_pmtu_disc;
};

extern struct ipv4_config ipv4_config;
#define IP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.ip_statistics, field)
#define IP_INC_STATS_BH(net, field)	SNMP_INC_STATS_BH((net)->mib.ip_statistics, field)
#define IP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.ip_statistics, field, val)
#define IP_ADD_STATS_BH(net, field, val) SNMP_ADD_STATS_BH((net)->mib.ip_statistics, field, val)
#define IP_UPD_PO_STATS(net, field, val) SNMP_UPD_PO_STATS((net)->mib.ip_statistics, field, val)
#define IP_UPD_PO_STATS_BH(net, field, val) SNMP_UPD_PO_STATS_BH((net)->mib.ip_statistics, field, val)
#define NET_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.net_statistics, field)
#define NET_INC_STATS_BH(net, field)	SNMP_INC_STATS_BH((net)->mib.net_statistics, field)
#define NET_INC_STATS_USER(net, field) 	SNMP_INC_STATS_USER((net)->mib.net_statistics, field)
#define NET_ADD_STATS_BH(net, field, adnd) SNMP_ADD_STATS_BH((net)->mib.net_statistics, field, adnd)
#define NET_ADD_STATS_USER(net, field, adnd) SNMP_ADD_STATS_USER((net)->mib.net_statistics, field, adnd)

extern unsigned long snmp_fold_field(void __percpu *mib[], int offt);
extern int snmp_mib_init(void __percpu *ptr[2], size_t mibsize);
extern void snmp_mib_free(void __percpu *ptr[2]);

extern struct local_ports {
	seqlock_t	lock;
	int		range[2];
} sysctl_local_ports;
extern void inet_get_local_port_range(int *low, int *high);

extern unsigned long *sysctl_local_reserved_ports;
static inline int inet_is_reserved_local_port(int port)
{
	return test_bit(port, sysctl_local_reserved_ports);
}

extern int sysctl_ip_default_ttl;
extern int sysctl_ip_nonlocal_bind;

extern struct ctl_path net_core_path[];
extern struct ctl_path net_ipv4_ctl_path[];

/* From inetpeer.c */
/* From inetpeer.c */
/*
 * 用于计算垃圾回收最大时间间隔及对端
 * 信息块生存期阈值。
 * 当前对端信息块数量大于此阈值时，使用
 * inet_peer_gc_mintime作为本次垃圾回收的时间间隔，
 * 否则根据inet_peer_gc_maxtime计算本次垃圾回收的
 * 时间间隔。
 * 当前对端信息块数大于此阈值时，使用
 * inet_peer_minttl作为本次垃圾回收的对端信息
 * 块生存期的阈值，否则根据inet_peer_maxttl
 * 计算本次垃圾回收对端信息块生存期
 * 的阈值。该参数默认值会根据系统内存
 * 大小动态调整，算法间inet_initpeers
 */
extern int inet_peer_threshold;
/*
 * 对端信息块的最短生存期。在有较大内存压力的
 * 情况下(如对端信息块的数量超过inet_peer_threshold的时候)，
 * 则使用inet_peer_minttl作为此次进行垃圾回收的对端信息
 * 块生存期的阈值。默认值为120.
 */
extern int inet_peer_minttl;
/*
 * 对端信息块的最长生存期。在没有内存压力的
 * 情况下(如对端信息块的数量很少时)，会使用
 * 较长的时间作为此次进行垃圾回收的对端信息
 * 块生存期的阈值，但不会大于inet_peer_maxttl。默认
 * 值为600.
 */
extern int inet_peer_maxttl;
/*
 * 进行垃圾回收的最小时间间隔。在有较大内存压力的
 * 情况下(如对端信息块的数量超过inet_peer_threshold时)，则
 * 使用inet_peer_gc_mintime作为此次进行垃圾回收的时间间隔。
 * 默认值为10.
 */
extern int inet_peer_gc_mintime;
/*
 * 进行垃圾回收的最大时间间隔。在没有内存压力的情况下(如
 * 对端信息块的数量很少的时候)，会晒用较长的时间作为此次
 * 进行垃圾回收的时间间隔，但不会大于inet_peer_gc_maxtime。默认值
 * 为120.
 */
extern int inet_peer_gc_maxtime;


/* From ip_output.c */
extern int sysctl_ip_dynaddr;

extern void ipfrag_init(void);

extern void ip_static_sysctl_init(void);

#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
int ip_dont_fragment(struct sock *sk, struct dst_entry *dst)
{
	return (inet_sk(sk)->pmtudisc == IP_PMTUDISC_DO ||
		(inet_sk(sk)->pmtudisc == IP_PMTUDISC_WANT &&
		 !(dst_metric_locked(dst, RTAX_MTU))));
}

extern void __ip_select_ident(struct iphdr *iph, struct dst_entry *dst, int more);

static inline void ip_select_ident(struct iphdr *iph, struct dst_entry *dst, struct sock *sk)
{
	if (iph->frag_off & htons(IP_DF)) {
		/* This is only to work around buggy Windows95/2000
		 * VJ compression implementations.  If the ID field
		 * does not change, they drop every other packet in
		 * a TCP stream using header compression.
		 */
		iph->id = (sk && inet_sk(sk)->inet_daddr) ?
					htons(inet_sk(sk)->inet_id++) : 0;
	} else
		__ip_select_ident(iph, dst, 0);
}

static inline void ip_select_ident_more(struct iphdr *iph, struct dst_entry *dst, struct sock *sk, int more)
{
	if (iph->frag_off & htons(IP_DF)) {
		if (sk && inet_sk(sk)->inet_daddr) {
			iph->id = htons(inet_sk(sk)->inet_id);
			inet_sk(sk)->inet_id += 1 + more;
		} else
			iph->id = 0;
	} else
		__ip_select_ident(iph, dst, more);
}

/*
 *	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;
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
#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 defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
	if (sk->sk_family == PF_INET6) {
		struct ipv6_pinfo *np = inet6_sk(sk);

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

#endif

static inline int sk_mc_loop(struct sock *sk)
{
	if (!sk)
		return 1;
	switch (sk->sk_family) {
	case AF_INET:
		return inet_sk(sk)->mc_loop;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
	case AF_INET6:
		return inet6_sk(sk)->mc_loop;
#endif
	}
	WARN_ON(1);
	return 1;
}

extern int	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
};

int ip_defrag(struct sk_buff *skb, u32 user);
int ip_frag_mem(struct net *net);
int ip_frag_nqueues(struct net *net);

/*
 *	Functions provided by ip_forward.c
 */
 
extern int ip_forward(struct sk_buff *skb);
 
/*
 *	Functions provided by ip_options.c
 */
 
extern void ip_options_build(struct sk_buff *skb, struct ip_options *opt, __be32 daddr, struct rtable *rt, int is_frag);
extern int ip_options_echo(struct ip_options *dopt, struct sk_buff *skb);
extern void ip_options_fragment(struct sk_buff *skb);
extern int ip_options_compile(struct net *net,
			      struct ip_options *opt, struct sk_buff *skb);
extern int ip_options_get(struct net *net, struct ip_options **optp,
			  unsigned char *data, int optlen);
extern int ip_options_get_from_user(struct net *net, struct ip_options **optp,
				    unsigned char __user *data, int optlen);
extern void ip_options_undo(struct ip_options * opt);
extern void ip_forward_options(struct sk_buff *skb);
extern int ip_options_rcv_srr(struct sk_buff *skb);

/*
 *	Functions provided by ip_sockglue.c
 */

extern int	ip_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
extern void	ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb);
extern int	ip_cmsg_send(struct net *net,
			     struct msghdr *msg, struct ipcm_cookie *ipc);
extern int	ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval, unsigned int optlen);
extern int	ip_getsockopt(struct sock *sk, int level, int optname, char __user *optval, int __user *optlen);
extern int	compat_ip_setsockopt(struct sock *sk, int level,
			int optname, char __user *optval, unsigned int optlen);
extern int	compat_ip_getsockopt(struct sock *sk, int level,
			int optname, char __user *optval, int __user *optlen);
extern int	ip_ra_control(struct sock *sk, unsigned char on, void (*destructor)(struct sock *));

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

/* sysctl helpers - any sysctl which holds a value that ends up being
 * fed into the routing cache should use these handlers.
 */
int ipv4_doint_and_flush(ctl_table *ctl, int write,
			 void __user *buffer,
			 size_t *lenp, loff_t *ppos);
int ipv4_doint_and_flush_strategy(ctl_table *table,
				  void __user *oldval, size_t __user *oldlenp,
				  void __user *newval, size_t newlen);
#ifdef CONFIG_PROC_FS
extern int ip_misc_proc_init(void);
#endif

#endif	/* _IP_H */