[unix-history] / sys / netinet / in_var.c

/*
 * Copyright (c) 1982, 1986, 1988 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	$Id$
 */

/*
 * This file attempts to centralize all the various variables that have
 * a hand in controlling the operation of IP and its ULPs.
 */

#include "param.h"
#include "systm.h"
#include "mbuf.h"
#include "domain.h"
#include "protosw.h"
#include "socket.h"
#include "time.h"
#include "net/if.h"
#include "net/route.h"

#include "in.h"
#include "in_systm.h"
#include "ip.h"
#include "in_pcb.h"
#include "in_var.h"
#include "ip_var.h"
#include "ip_icmp.h"
#include "icmp_var.h"


/*
 * IPFORWARDING controls whether the IP layer will forward packets received
 * by us but not addressed to one of our addresses.
 *
 * IPSENDREDIRECTS controls whether the IP layer will send ICMP Redirect
 * messages.
 *
 * GATEWAY turns both of these on, and also allocates more memory for some
 * networking functions.
 */

#ifndef	IPFORWARDING
#ifdef GATEWAY
#define	IPFORWARDING	1	/* forward IP packets not for us */
#else /* not GATEWAY */
#define	IPFORWARDING	0	/* don't forward IP packets not for us */
#endif /* not GATEWAY */
#endif /* not IPFORWARDING */

/*
 * NB: RFC 1122, ``Requirements for Internet Hosts: Communication Layers'',
 * absolutely forbids hosts (which are not acting as gateways) from sending
 * ICMP redirects.
 */
#ifndef	IPSENDREDIRECTS
#ifdef GATEWAY
#define	IPSENDREDIRECTS	1
#else /* not GATEWAY */
#define IPSENDREDIRECTS 0
#endif /* not GATEWAY */
#endif /* not IPSENDREDIRECTS */

int	ipforwarding = IPFORWARDING;
int	ipsendredirects = IPSENDREDIRECTS;
#ifdef DIAGNOSTIC
int	ipprintfs = 0;
#endif

/*
 * ip_protox[] maps from IP protocol number to an index in inetsw[].
 */
u_char	ip_protox[IPPROTO_MAX];

/*
 * ipqmaxlen is the maximum length of the IP input queue.
 * ipintrq is the queue itself.
 */
struct ifqueue ipintrq;
int	ipqmaxlen = IFQ_MAXLEN;

/*
 * the IP reassembly queue
 */
struct	ipq ipq;

/*
 * in_ifaddr points to a linked list of IP interface addresses, managed
 * by the code in in.c.
 */
struct	in_ifaddr *in_ifaddr;			/* first inet address */

/*
 * statistics for netstat and management
 */
struct	ipstat ipstat;

/*
 * ip_id is the next IP packet id number to be assigned (used in fragmentation
 * and reassembly).
 */
u_short ip_id;

/*
 * When acting as a gateway, the IP layer keeps track of how many packets
 * are forwarded for each (in-ifp, out-ifp) pair.  This code needs to get
 * updated or junked now that interfaces can come and go like the wind.
 * (in ip_input.c)
 */
#ifdef GATEWAY
u_long	*ip_ifmatrix;
#endif

/*
 * ipaddr is a sockaddr_in used by various bits of code when they
 * need to convert a `struct in_addr' to a `struct sockaddr_in'.
 *
 * ipforward_rt is a route used when forwarding packets.  It functions
 * as a route cache of order one, if you want to think of it that way.
 */
struct	sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
struct	route ipforward_rt;

/*
 * inetctlerrmap[] maps control input commands to errno values.  0 means
 * don't signal error.
 */
u_char inetctlerrmap[PRC_NCMDS] = {
	0,			/* ifdown */
	0,			/* routedead */
	0,			/* #2 */
	0,			/* quench2 */
	0,			/* quench */
	EMSGSIZE,		/* msgsize */
	EHOSTDOWN,		/* hostdead */
	EHOSTUNREACH,		/* hostunreach */
	EHOSTUNREACH,		/* unreachnet */
	EHOSTUNREACH,		/* unreachhost */
	ECONNREFUSED,		/* unreachproto */
	ECONNREFUSED,		/* unreachport */
	EMSGSIZE,		/* old needfrag */
	EHOSTUNREACH,		/* srcfail */
	EHOSTUNREACH,		/* netunknown */
	EHOSTUNREACH,		/* hostunknown */
	EHOSTUNREACH,		/* isolated */
	ECONNREFUSED,		/* net admin. prohibited */
	ECONNREFUSED,		/* host admin. prohibited */
	EHOSTUNREACH,		/* tos net unreachable */
	EHOSTUNREACH,		/* tos host unreachable */
	0,			/* redirect net */
	0,			/* redirect host */
	0,			/* redirect tosnet */
	0,			/* redirect toshost */
	0,			/* time exceeded */
	0,			/* reassembly timeout */
	ENOPROTOOPT,		/* parameter problem */
	ENOPROTOOPT,		/* required option missing */
	0,			/* MTU changed */
	/* NB: this means that this error will only
	   get propagated by in_mtunotify(), which
	   doesn't bother to check. */
};

/*
 * SUBNETSARELOCAL determines where IP subnets are considered to be ``local''
 * or not.  This option is obsolete.
 */
#ifndef SUBNETSARELOCAL
#define	SUBNETSARELOCAL	1
#endif
int subnetsarelocal = SUBNETSARELOCAL;

#ifdef MTUDISC
/*
 * MTUTIMER1 is the number of minutes to wait after having incremented
 * the MTU estimate before trying again.  MTUTIMER2 is the number
 * of minutes to wait after having decremented the MTU estimate
 * before trying to increment it.
 */
#ifndef MTUTIMER1
#define MTUTIMER1 2
#endif
int in_mtutimer1 = MTUTIMER1;

#ifndef MTUTIMER2
#define MTUTIMER2 10
#endif
int in_mtutimer2 = MTUTIMER2;
#endif /* MTUDISC */

/*
 * and a zero in_addr to make some code happy...
 */
struct	in_addr zeroin_addr;

/*
 * ICMPPRINTFS enables some debugging printfs in ip_icmp.c.
 *
 * IPBROADCASTECHO controls whether ICMP Echo Reply packets are sent
 * in response to ICMP Echo packets which were addressed to a multicast
 * or broadcast address.
 *
 * IPMASKAGENT controls whether ICMP Mask Reply packets are sent.
 * It should only be enabled on the machine which is the authoritative
 * mask agent for a subnet.
 */
#ifdef ICMPPRINTFS
int	icmpprintfs = 0;
#endif

#ifndef IPBROADCASTECHO
#define IPBROADCASTECHO 0
#endif
int	ipbroadcastecho = IPBROADCASTECHO;

#ifndef IPMASKAGENT
#define IPMASKAGENT 0
#endif
int	ipmaskagent = IPMASKAGENT;

/*
 * ICMP statistics
 */
struct icmpstat icmpstat;

/*
 * Yet Another sockaddr_in filled in by various routines when convenient.
 */
struct sockaddr_in icmpmask = { 8, 0 };

/*
 * Print out TCP debugging messages on the console.
 */
#ifdef TCPDEBUG
int	tcpconsdebug = 0;
#endif

#include "tcp.h"
#include "tcp_fsm.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"
#include "tcpip.h"

/*
 * tcp_ttl is the default IP TTL for TCP segments.
 * tcp_mssdflt is the default max segment size.
 * tcp_rttdflt is the initial round trip time estimate when there is no RTT
 * in the route.
 */
int	tcp_ttl = TCP_TTL;
int 	tcp_mssdflt = TCP_MSS;
int 	tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;

/*
 * When KPROF is defined (god only knows why), TCP keeps track of
 * protocol requests in this matrix.
 */
#ifdef KPROF
int	tcp_acounts[TCP_NSTATES][PRU_NREQ];
#endif

/*
 * tcp_keepidle is the a fraction of the length of non-response time in a 
 * in a keepalive situation after which TCP abandons the connection.
 *
 * tcp_keepintvl is the interval between keepalives.
 *
 * tcp_maxidle is the time after which a connection will be dropped in
 * certain states.  It is computed as `TCPTV_KEEPCNT * tcp_keepintvl'.
 */
int	tcp_keepidle = TCPTV_KEEP_IDLE;
int	tcp_keepintvl = TCPTV_KEEPINTVL;
int	tcp_maxidle;

/*
 * tcp_sendspace and tcp_recvspace are the default send and receive window
 * sizes, respectively.  These are obsolescent (this information should
 * be set by the route).
 */
#ifdef	TCP_SMALLSPACE
u_long	tcp_sendspace = 1024*4;
u_long	tcp_recvspace = 1024*4;
#else
u_long	tcp_sendspace = 1024*16;
u_long	tcp_recvspace = 1024*16;
#endif	/* TCP_SMALLSPACE */

#include "udp.h"
#include "udp_var.h"

/*
 * udpcksum tells whether to do UDP checksums.  It should always be
 * turned on, except as required for compatibility with ancient
 * 4.2-based systems like SunOS 3.5 and Ultrix 2.0.
 */
#ifndef	COMPAT_42
int	udpcksum = 1;
#else
int	udpcksum = 0;		/* XXX */
#endif


/*
 * udp_ttl is the default IP TTL for UDP packets.
 */
int	udp_ttl = UDP_TTL;

/*
 * UDP statistics for netstat.
 */
struct	udpstat udpstat;

/*
 * udp_sendspace is the maximum datagram size the UDP layer is willing to
 * attempt to transmit.
 *
 * udp_recvspace is the amount of buffer space the UDP layer will
 * reserve for holding received packets.
 */
u_long	udp_sendspace = 9216;		/* really max datagram size */
u_long	udp_recvspace = 40 * (1024 + sizeof(struct sockaddr_in));
					/* 40 1K datagrams */
Commit	Line	Data
afc905cd GW	1	/*
	2	* Copyright (c) 1982, 1986, 1988 Regents of the University of California.
	3	* All rights reserved.
	4	*
	5	* Redistribution and use in source and binary forms, with or without
	6	* modification, are permitted provided that the following conditions
	7	* are met:
	8	* 1. Redistributions of source code must retain the above copyright
	9	* notice, this list of conditions and the following disclaimer.
	10	* 2. Redistributions in binary form must reproduce the above copyright
	11	* notice, this list of conditions and the following disclaimer in the
	12	* documentation and/or other materials provided with the distribution.
	13	* 3. All advertising materials mentioning features or use of this software
	14	* must display the following acknowledgement:
	15	* This product includes software developed by the University of
	16	* California, Berkeley and its contributors.
	17	* 4. Neither the name of the University nor the names of its contributors
	18	* may be used to endorse or promote products derived from this software
	19	* without specific prior written permission.
	20	*
	21	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	22	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	23	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	24	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	25	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	26	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	27	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	28	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	29	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	30	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	31	* SUCH DAMAGE.
	32	*
	33	* $Id$
	34	*/
	35
	36	/*
	37	* This file attempts to centralize all the various variables that have
	38	* a hand in controlling the operation of IP and its ULPs.
	39	*/
	40
	41	#include "param.h"
	42	#include "systm.h"
	43	#include "mbuf.h"
	44	#include "domain.h"
	45	#include "protosw.h"
	46	#include "socket.h"
	47	#include "time.h"
	48	#include "net/if.h"
	49	#include "net/route.h"
	50
	51	#include "in.h"
	52	#include "in_systm.h"
	53	#include "ip.h"
	54	#include "in_pcb.h"
	55	#include "in_var.h"
	56	#include "ip_var.h"
	57	#include "ip_icmp.h"
	58	#include "icmp_var.h"
	59
	60
	61	/*
	62	* IPFORWARDING controls whether the IP layer will forward packets received
	63	* by us but not addressed to one of our addresses.
	64	*
65	* IPSENDREDIRECTS controls whether the IP layer will send ICMP Redirect
66	* messages.
67	*
68	* GATEWAY turns both of these on, and also allocates more memory for some
69	* networking functions.
70	*/
71
72	#ifndef IPFORWARDING
73	#ifdef GATEWAY
74	#define IPFORWARDING 1 /* forward IP packets not for us */
75	#else /* not GATEWAY */
76	#define IPFORWARDING 0 /* don't forward IP packets not for us */
77	#endif /* not GATEWAY */
78	#endif /* not IPFORWARDING */
79
80	/*
81	* NB: RFC 1122, ``Requirements for Internet Hosts: Communication Layers'',
82	* absolutely forbids hosts (which are not acting as gateways) from sending
83	* ICMP redirects.
84	*/
85	#ifndef IPSENDREDIRECTS
86	#ifdef GATEWAY
87	#define IPSENDREDIRECTS 1
88	#else /* not GATEWAY */
89	#define IPSENDREDIRECTS 0
90	#endif /* not GATEWAY */
91	#endif /* not IPSENDREDIRECTS */
92
93	int ipforwarding = IPFORWARDING;
94	int ipsendredirects = IPSENDREDIRECTS;
95	#ifdef DIAGNOSTIC
96	int ipprintfs = 0;
97	#endif
98
99	/*
100	* ip_protox[] maps from IP protocol number to an index in inetsw[].
101	*/
102	u_char ip_protox[IPPROTO_MAX];
103
104	/*
105	* ipqmaxlen is the maximum length of the IP input queue.
106	* ipintrq is the queue itself.
107	*/
108	struct ifqueue ipintrq;
109	int ipqmaxlen = IFQ_MAXLEN;
110
111	/*
112	* the IP reassembly queue
113	*/
114	struct ipq ipq;
115
116	/*
117	* in_ifaddr points to a linked list of IP interface addresses, managed
118	* by the code in in.c.
119	*/
120	struct in_ifaddr in_ifaddr; / first inet address */
121
122	/*
123	* statistics for netstat and management
124	*/
125	struct ipstat ipstat;
126
127	/*
128	* ip_id is the next IP packet id number to be assigned (used in fragmentation
129	* and reassembly).
130	*/
131	u_short ip_id;
132
133	/*
134	* When acting as a gateway, the IP layer keeps track of how many packets
135	* are forwarded for each (in-ifp, out-ifp) pair. This code needs to get
136	* updated or junked now that interfaces can come and go like the wind.
137	* (in ip_input.c)
138	*/
139	#ifdef GATEWAY
140	u_long *ip_ifmatrix;
141	#endif
142
143	/*
144	* ipaddr is a sockaddr_in used by various bits of code when they
145	* need to convert a `struct in_addr' to a `struct sockaddr_in'.
146	*
147	* ipforward_rt is a route used when forwarding packets. It functions
148	* as a route cache of order one, if you want to think of it that way.
149	*/
150	struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
151	struct route ipforward_rt;
152
153	/*
154	* inetctlerrmap[] maps control input commands to errno values. 0 means
155	* don't signal error.
156	*/
157	u_char inetctlerrmap[PRC_NCMDS] = {
158	0, /* ifdown */
159	0, /* routedead */
160	0, /* #2 */
161	0, /* quench2 */
162	0, /* quench */
163	EMSGSIZE, /* msgsize */
164	EHOSTDOWN, /* hostdead */
165	EHOSTUNREACH, /* hostunreach */
166	EHOSTUNREACH, /* unreachnet */
167	EHOSTUNREACH, /* unreachhost */
168	ECONNREFUSED, /* unreachproto */
169	ECONNREFUSED, /* unreachport */
170	EMSGSIZE, /* old needfrag */
171	EHOSTUNREACH, /* srcfail */
172	EHOSTUNREACH, /* netunknown */
173	EHOSTUNREACH, /* hostunknown */
174	EHOSTUNREACH, /* isolated */
175	ECONNREFUSED, /* net admin. prohibited */
176	ECONNREFUSED, /* host admin. prohibited */
177	EHOSTUNREACH, /* tos net unreachable */
178	EHOSTUNREACH, /* tos host unreachable */
179	0, /* redirect net */
180	0, /* redirect host */
181	0, /* redirect tosnet */
182	0, /* redirect toshost */
183	0, /* time exceeded */
184	0, /* reassembly timeout */
185	ENOPROTOOPT, /* parameter problem */
186	ENOPROTOOPT, /* required option missing */
187	0, /* MTU changed */
188	/* NB: this means that this error will only
189	get propagated by in_mtunotify(), which
190	doesn't bother to check. */
191	};
192
193	/*
194	* SUBNETSARELOCAL determines where IP subnets are considered to be ``local''
195	* or not. This option is obsolete.
196	*/
197	#ifndef SUBNETSARELOCAL
198	#define SUBNETSARELOCAL 1
199	#endif
200	int subnetsarelocal = SUBNETSARELOCAL;
201
202	#ifdef MTUDISC
203	/*
204	* MTUTIMER1 is the number of minutes to wait after having incremented
205	* the MTU estimate before trying again. MTUTIMER2 is the number
206	* of minutes to wait after having decremented the MTU estimate
207	* before trying to increment it.
208	*/
209	#ifndef MTUTIMER1
210	#define MTUTIMER1 2
211	#endif
212	int in_mtutimer1 = MTUTIMER1;
213
214	#ifndef MTUTIMER2
215	#define MTUTIMER2 10
216	#endif
217	int in_mtutimer2 = MTUTIMER2;
218	#endif /* MTUDISC */
219
220	/*
221	* and a zero in_addr to make some code happy...
222	*/
223	struct in_addr zeroin_addr;
224
225	/*
226	* ICMPPRINTFS enables some debugging printfs in ip_icmp.c.
227	*
228	* IPBROADCASTECHO controls whether ICMP Echo Reply packets are sent
229	* in response to ICMP Echo packets which were addressed to a multicast
230	* or broadcast address.
231	*
232	* IPMASKAGENT controls whether ICMP Mask Reply packets are sent.
233	* It should only be enabled on the machine which is the authoritative
234	* mask agent for a subnet.
235	*/
236	#ifdef ICMPPRINTFS
237	int icmpprintfs = 0;
238	#endif
239
240	#ifndef IPBROADCASTECHO
241	#define IPBROADCASTECHO 0
242	#endif
243	int ipbroadcastecho = IPBROADCASTECHO;
244
245	#ifndef IPMASKAGENT
246	#define IPMASKAGENT 0
247	#endif
248	int ipmaskagent = IPMASKAGENT;
249
250	/*
251	* ICMP statistics
252	*/
253	struct icmpstat icmpstat;
254
255	/*
256	* Yet Another sockaddr_in filled in by various routines when convenient.
257	*/
258	struct sockaddr_in icmpmask = { 8, 0 };
259
260	/*
261	* Print out TCP debugging messages on the console.
262	*/
263	#ifdef TCPDEBUG
264	int tcpconsdebug = 0;
265	#endif
266
267	#include "tcp.h"
268	#include "tcp_fsm.h"
269	#include "tcp_seq.h"
270	#include "tcp_timer.h"
271	#include "tcp_var.h"
272	#include "tcpip.h"
273
274	/*
275	* tcp_ttl is the default IP TTL for TCP segments.
276	* tcp_mssdflt is the default max segment size.
277	* tcp_rttdflt is the initial round trip time estimate when there is no RTT
278	* in the route.
279	*/
280	int tcp_ttl = TCP_TTL;
281	int tcp_mssdflt = TCP_MSS;
282	int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
283
284	/*
285	* When KPROF is defined (god only knows why), TCP keeps track of
286	* protocol requests in this matrix.
287	*/
288	#ifdef KPROF
289	int tcp_acounts[TCP_NSTATES][PRU_NREQ];
290	#endif
291
292	/*
293	* tcp_keepidle is the a fraction of the length of non-response time in a
294	* in a keepalive situation after which TCP abandons the connection.
295	*
296	* tcp_keepintvl is the interval between keepalives.
297	*
298	* tcp_maxidle is the time after which a connection will be dropped in
299	* certain states. It is computed as `TCPTV_KEEPCNT * tcp_keepintvl'.
300	*/
301	int tcp_keepidle = TCPTV_KEEP_IDLE;
302	int tcp_keepintvl = TCPTV_KEEPINTVL;
303	int tcp_maxidle;
304
305	/*
306	* tcp_sendspace and tcp_recvspace are the default send and receive window
307	* sizes, respectively. These are obsolescent (this information should
308	* be set by the route).
309	*/
310	#ifdef TCP_SMALLSPACE
311	u_long tcp_sendspace = 1024*4;
312	u_long tcp_recvspace = 1024*4;
313	#else
314	u_long tcp_sendspace = 1024*16;
315	u_long tcp_recvspace = 1024*16;
316	#endif /* TCP_SMALLSPACE */
317
318	#include "udp.h"
319	#include "udp_var.h"
320
321	/*
322	* udpcksum tells whether to do UDP checksums. It should always be
323	* turned on, except as required for compatibility with ancient
324	* 4.2-based systems like SunOS 3.5 and Ultrix 2.0.
325	*/
326	#ifndef COMPAT_42
327	int udpcksum = 1;
328	#else
329	int udpcksum = 0; /* XXX */
330	#endif
331
332
333	/*
334	* udp_ttl is the default IP TTL for UDP packets.
335	*/
336	int udp_ttl = UDP_TTL;
337
338	/*
339	* UDP statistics for netstat.
340	*/
341	struct udpstat udpstat;
342
343	/*
344	* udp_sendspace is the maximum datagram size the UDP layer is willing to
345	* attempt to transmit.
346	*
347	* udp_recvspace is the amount of buffer space the UDP layer will
348	* reserve for holding received packets.
349	*/
350	u_long udp_sendspace = 9216; /* really max datagram size */
351	u_long udp_recvspace = 40 * (1024 + sizeof(struct sockaddr_in));
352	/* 40 1K datagrams */
353
354