1.\u4e2d\u5fc3\u73af\u8282<\/p>\n
\tIP\u662f\u6574\u4e2a\u534f\u8bae\u8f6f\u4ef6\u7684\u4e2d\u5fc3\u73af\u8282,\u4e0d\u8981\u628aIP\u8f6f\u4ef6\u7b80\u5355\u7684\u5206\u5272\u6210\u8f93\u5165\u548c\u8f93\u51fa\u4e24\u90e8\u5206,\u56e0\u4e3a\u8f93\u5165\u548c\u8f93\u51fa\u7684\u754c\u9650\u5f88\u6a21\u7cca.\u4ee5\u4e0b\u628a\u91cd\u70b9\u653e\u5728\u7f51\u5173\u4e0a.<\/p>\n
\n\t2. IP\u8f6f\u4ef6\u8bbe\u8ba1\u601d\u60f3<\/p>\n
\t * \u7edf\u4e00\u7684\u8f93\u5165\u961f\u5217\u4ee5\u53ca\u7edf\u4e00\u7684\u9009\u8def\u8fc7\u7a0b
\n\t * \u72ec\u7acb\u7684IP\u8fdb\u7a0b
\n\t * \u672c\u5730\u4e3b\u673a\u63a5\u53e3<\/p>\n
\n\t3. IP\u8f6f\u4ef6\u7ed3\u6784\u548c\u6570\u636e\u62a5\u6d41\u7a0b<\/p>\n
\t4. IP\u8f6f\u4ef6\u7ed3\u6784\u548c\u6570\u636e\u62a5\u6d41\u7a0b<\/p>\n
\t4.1 \u9009\u62e9\u4f20\u5165\u6570\u636e\u62a5\u7684\u7b56\u7565
\n\t\u6311\u9009\u6570\u636e\u62a5\u5e76\u4e3a\u5176\u9009\u62e9\u8def\u7531\u7684IP\u7a0b\u5e8f\u6bb5\u5b9e\u73b0\u4e86\u4e00\u4e2a\u91cd\u8981\u7b56\u7565:\u5b83\u51b3\u5b9a\u4e86\u6570\u636e\u62a5\u6765\u6e90\u7684\u76f8\u5bf9\u4f18\u5148\u7ea7.
\n\t\u516c\u5e73\u5206\u914d\u4f18\u5148\u6743,\u4f8b\u7528\u7b56\u7565\u4e3a\u5faa\u73af\u6cd5(round-robin)<\/p>\n
\t\/* ipgetp.c – ipgetp *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h>
\n\t#include <proc.h><\/p>\n
\tstatic int ifnext = NI_LOCAL; \/\/\u63a5\u53e3\u7d22\u5f15<\/p>\n
\t\/*————————————————————————
\n\t * ipgetp — choose next IP input queue and extract a packet
\n\t *————————————————————————
\n\t *\/
\n\tstruct ep *
\n\tipgetp(int *pifnum)
\n\t{
\n\t struct ep *pep; \/\/\u4ee5\u592a\u5e27\u7ed3\u6784\u4f53
\n\t int i;<\/p>\n
\t recvclr(); \/* \u786e\u4fdd\u6ca1\u6709\u65e7\u5206\u7ec4\u6b63\u5728\u7b49\u5f85 *\/
\n\t while (TRUE) {
\n\t for (i=0; i < Net.nif; ++i, ++ifnext) { \/\/\u904d\u5386\u6bcf\u4e2a\u63a5\u53e3
\n\t if (ifnext >= Net.nif) \/\/\u7b49\u4e8e\u6216\u5927\u4e8e\u6700\u5927\u63a5\u53e3\u6570
\n\t ifnext = 0;
\n\t if (nif[ifnext].ni_state == NIS_DOWN) \/\/\u6b64\u63a5\u53e3\u5173\u95ed
\n\t continue;
\n\t if (pep = NIGET(ifnext)) { \/*NIGET\u5b8f,\u63d0\u53d6\u5e76\u8fd4\u56de\u7b2c\u4e00\u4e2a\u6570\u636e*\/
\n\t *pifnum = ifnext; \/\/\u8fd4\u56de\u63a5\u53e3\u7684\u5e8f\u53f7
\n\t return pep; \/\/\u8fd4\u56de\u4ee5\u592a\u5e27\u7684\u7ed3\u6784\u4f53\u6307\u9488
\n\t }
\n\t }
\n\t ifnext = receive(); \/\/\u5982\u6ca1\u6709\u6570\u636e\u5219\u963b\u585e,\u5f53\u6709\u6570\u636e\u5230\u8fbe\u65f6,\u8fd4\u56de\u6570\u636e\u62a5\u5230\u8fbe\u7684\u63a5\u53e3\u6307\u5411
\n\t }
\n\t \/* can't reach here *\/
\n\t}<\/p>\n
\t4.2 IP\u4f7f\u7528\u7684\u5e38\u91cf\u5b9a\u4e49<\/p>\n
\t\/* ip.h – IP_HLEN, IP_CLASS{A,B,C,D,E} *\/<\/p>\n
\t\/* \u4e92\u8054\u7f51\u534f\u8bae\uff08IP\uff09\u7684\u5e38\u91cf\u548c\u6570\u636e\u62a5\u683c\u5f0f *\/<\/p>\n
\t#define IP_ALEN 4 \/* \u4ee5\u5b57\u8282\u4e3a\u5355\u4f4d\u7684IP\u5730\u5740\u7684\u957f\u5ea6\uff08\u5b57\u8282\uff09 *\/
\n\ttypedef unsigned long IPaddr; \/* \u4e92\u8054\u7f51\u5730\u5740 *\/<\/p>\n
\t#if BYTE_ORDER == BIG_ENDIAN
\n\t#define IP_CLASSA(x) (((x) & 0x80000000) == 0) \/* A\u7c7b\u7684IP *\/
\n\t#define IP_CLASSB(x) (((x) & 0xc0000000) == 0x80000000) \/* B\u7c7b\u7684IP *\/
\n\t#define IP_CLASSC(x) (((x) & 0xe0000000) == 0xc0000000) \/* C\u7c7b\u7684IP *\/
\n\t#define IP_CLASSD(x) (((x) & 0xf0000000) == 0xe0000000) \/* D\u7c7b\u7684IP *\/
\n\t#define IP_CLASSE(x) (((x) & 0xf8000000) == 0xf0000000) \/* E\u7c7b\u7684IP *\/
\n\t#else \/* BYTE_ORDER *\/
\n\t#define IP_CLASSA(x) (((x) & 0x80) == 0x00) \/* A\u7c7b\u7684IP\u5730\u5740 *\/
\n\t#define IP_CLASSB(x) (((x) & 0xc0) == 0x80) \/* B\u7c7b\u7684IP\u5730\u5740 *\/
\n\t#define IP_CLASSC(x) (((x) & 0xe0) == 0xc0) \/* C\u7c7b\u7684IP\u5730\u5740 *\/
\n\t#define IP_CLASSD(x) (((x) & 0xf0) == 0xe0) \/* D\u7c7b\u7684IP\u5730\u5740 *\/
\n\t#define IP_CLASSE(x) (((x) & 0xf8) == 0xf0) \/* E\u7c7b\u7684IP\u5730\u5740 *\/
\n\t#endif \/* BYTE_ORDER *\/<\/p>\n
\t\/* \u90e8\u5206\u5206\u914d\u534f\u8bae\u7f16\u53f7 *\/<\/p>\n
\t#define IPT_ICMP 1 \/* ICMP\u6570\u636e\u5305\u534f\u8bae\u7c7b\u578b *\/
\n\t#define IPT_IGMP 2 \/* IGMP\u6570\u636e\u5305\u534f\u8bae\u7c7b\u578b *\/
\n\t#define IPT_TCP 6 \/* TCP\u6570\u636e\u5305\u534f\u8bae\u7c7b\u578b *\/
\n\t#define IPT_EGP 8 \/* EGP\u6570\u636e\u5305\u534f\u8bae\u7c7b\u578b *\/
\n\t#define IPT_UDP 17 \/* UDP\u6570\u636e\u5305\u7684\u534f\u8bae\u7c7b\u578b *\/
\n\t#define IPT_OSPF 89 \/* OSPF\u6570\u636e\u5305\u534f\u8bae\u7c7b\u578b *\/<\/p>\n
\tstruct ip {
\n\t u_char ip_verlen; \/* IP\u7248\u672c\u53ca\u5934\u957f\u5ea6 (in longs)*\/
\n\t u_char ip_tos; \/* \u670d\u52a1\u7c7b\u578b *\/
\n\t u_short ip_len; \/* \u5305\u603b\u957f\u5ea6\uff08\u5b57\u8282\uff09 *\/
\n\t short ip_id; \/* \u6570\u636e\u5305\u7684id *\/
\n\t short ip_fragoff; \/* \u788e\u7247\u504f\u79fb\uff088\u5b57\u8282\u7684\uff09 *\/
\n\t u_char ip_ttl; \/* \u751f\u5b58\u65f6\u95f4\uff0c\u5728\u7f51\u5173\u7684\u8df3 *\/
\n\t u_char ip_proto; \/* IP\u534f\u8bae\uff08\u89c1IPT_ *\uff09*\/
\n\t short ip_cksum; \/* \u5934\u6821\u9a8c\u548c *\/
\n\t IPaddr ip_src; \/* \u6e90IP\u5730\u5740 *\/
\n\t IPaddr ip_dst; \/* \u76ee\u7684\u5730IP\u5730\u5740 *\/
\n\t u_char ip_data[1]; \/* \u53ef\u53d8\u957f\u5ea6\u7684\u6570\u636e *\/
\n\t};<\/p>\n
\t#define IP_VERSION 4 \/* \u5f53\u524d\u7248\u672c\u503c *\/
\n\t#define IP_MINHLEN 5 \/* \u6700\u5c0f\u7684IP\u5934\u957f\u5ea6 (in longs) *\/
\n\t#define IP_TTL 255 \/* \u751f\u5b58\u65f6\u95f4\u521d\u59cb\u503c *\/<\/p>\n
\t#define IP_MF 0x2000 \/* \u66f4\u591a\u7684\u788e\u7247\u4f4d *\/
\n\t#define IP_DF 0x4000 \/* \u4e0d\u5206\u7247\u4f4d *\/
\n\t#define IP_FRAGOFF 0x1fff \/* \u788e\u7247\u504f\u79fb fragment offset mask*\/
\n\t#define IP_PREC 0xe0 \/* \u4f18\u5148\u7684\u670d\u52a1 precedence portion of TOS*\/<\/p>\n
\t\/* IP\u4f18\u5148\u503c *\/<\/p>\n
\t#define IPP_NETCTL 0xe0 \/* \u7f51\u7edc\u63a7\u5236 *\/
\n\t#define IPP_INCTL 0xc0 \/* Internet\u63a7\u5236 *\/
\n\t#define IPP_CRIT 0xa0 \/* \u5173\u952e critical *\/
\n\t#define IPP_FLASHO 0x80 \/* flash over-ride *\/
\n\t#define IPP_FLASH 0x60 \/* flash *\/
\n\t#define IPP_IMMED 0x40 \/* immediate *\/
\n\t#define IPP_PRIO 0x20 \/* \u4f18\u5148 *\/
\n\t#define IPP_NORMAL 0x00 \/* \u6b63\u5e38 *\/<\/p>\n
\t\/*\u5b8f\u6765\u8ba1\u7b97\u4e00\u4e2a\u6570\u636e\u62a5\u7684\u62a5\u5934\u7684\u957f\u5ea6\uff08\u5b57\u8282\uff09 *\/
\n\t#define IP_HLEN(pip) ((pip->ip_verlen & 0xf)<<2)
\n\t#define IPMHLEN 20 \/* \u6700\u5c0f\u7684IP\u5934\u957f\u5ea6\uff08\u5b57\u8282\uff09 *\/<\/p>\n
\t\/* IP\u9009\u9879 *\/
\n\t#define IPO_COPY 0x80 \/* \u5206\u7247\u590d\u5236 copy on fragment mask *\/
\n\t#define IPO_CLASS 0x60 \/* \u9009\u9879\u7c7b option class *\/
\n\t#define IPO_NUM 0x17 \/* \u9009\u9879\u7f16\u53f7option number *\/<\/p>\n
\t#define IPO_EOOP 0x00 \/* \u9009\u9879\u7ed3\u675f *\/
\n\t#define IPO_NOP 0x01 \/* \u6ca1\u6709\u64cd\u4f5c no operation *\/
\n\t#define IPO_SEC 0x82 \/* DoD security\/compartmentalization *\/
\n\t#define IPO_LSRCRT 0x83 \/* \u677e\u6563\u6e90\u8def\u7531 loose source routing *\/
\n\t#define IPO_SSRCRT 0x89 \/* \u4e25\u683c\u7684\u6e90\u8def\u7531strict source routing *\/
\n\t#define IPO_RECRT 0x07 \/* \u8bb0\u5f55\u8def\u7ebf *\/
\n\t#define IPO_STRID 0x88 \/* \u6d41\u7f16\u53f7 *\/
\n\t#define IPO_TIME 0x44 \/* \u4e92\u8054\u7f51\u65f6\u95f4\u6233 *\/<\/p>\n
\t#define IP_MAXLEN BPMAXB-EP_HLEN \/* IP\u6570\u636e\u62a5\u7684\u6700\u5927\u957f\u5ea6 *\/<\/p>\n
\t\/*IP\u8fdb\u7a0b\u7684\u4fe1\u606f *\/<\/p>\n
\textern PROCESS ipproc();
\n\t#define IPSTK 512 \/* IP\u8fc7\u7a0b\u5806\u6808\u5927\u5c0f *\/
\n\t#define IPPRI 100 \/* IP\u8fd0\u884c\u5728\u9ad8\u4f18\u5148\u7ea7 *\/
\n\t#define IPNAM "ip" \/* IP\u8fc7\u7a0b\u7684\u540d\u5b57 *\/
\n\t#define IPARGC 0 \/* count of args to IP *\/<\/p>\n
\textern IPaddr ip_maskall; \/* = 255.255.255.255 *\/
\n\textern IPaddr ip_anyaddr; \/* = 0.0.0.0 *\/
\n\textern IPaddr ip_loopback; \/* = 127.0.0.1 *\/<\/p>\n
\textern int ippid, gateway;<\/p>\n
\tstruct ip *iph2net(struct ip *), *ipnet2h(struct ip *);
\n\tunsigned short cksum(WORD *, unsigned);
\n\tint ipsend(IPaddr, struct ep *, unsigned, u_char, u_char, u_char);
\n\tint ipputp(unsigned, IPaddr, struct ep *);
\n\tBool isbrc(IPaddr);<\/p>\n
\t4.3 IP\u8fdb\u7a0b\u7684\u7ed3\u6784 (IP\u8fdb\u7a0b\u5141\u8bb8\u88ab\u963b\u585e)<\/p>\n
\t\/* ipproc.c – ipproc *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h><\/p>\n
\tstruct ep *ipgetp(int *);
\n\tstruct route *rtget(IPaddr, Bool);<\/p>\n
\t\/*————————————————————————
\n\t * ipproc – \u5904\u7406\u4e00\u4e2a\u4ece\u7f51\u7edc\u4e2d\u6765\u7684IP\u6570\u636e\u5305
\n\t *————————————————————————
\n\t *\/
\n\tPROCESS
\n\tipproc(void)
\n\t{
\n\t struct ep *pep;
\n\t struct ip *pip;
\n\t struct route *prt;
\n\t Bool nonlocal;
\n\t int ifnum;<\/p>\n
\t ippid = getpid(); \/* \u5f97\u5230\u8fdb\u7a0b\u7684ID *\/<\/p>\n
\t signal(Net.sema); \/* \u4fe1\u53f7\u8fdb\u884c\u521d\u59cb\u5316*\/<\/p>\n
\t while (TRUE) {
\n\t pep = ipgetp(&ifnum); \/* \u9009\u53d6\u4e00\u4e2a\u4ee5\u592a\u7f51\u6570\u636e\u62a5*\/
\n\t pip = (struct ip *)pep->ep_data; \/* \u5f97\u5230\u6b64\u62a5\u5305\u542b\u7684\u66f4\u9ad8\u7ea7\u62a5\u5730\u5740*\/<\/p>\n
\t if ((pip->ip_verlen>>4) != IP_VERSION) { \/* \u5224\u65ad\u662f\u5426\u4e3aIP\u6570\u636e\u62a5*\/
\n\t IpInHdrErrors++;
\n\t freebuf(pep);
\n\t continue;
\n\t }
\n\t if (IP_CLASSE(pip->ip_dst)) { \/* \u5224\u65ad\u662f\u5426\u4e3aE\u7c7b\u5730\u5740*\/
\n\t IpInAddrErrors++;
\n\t freebuf(pep);
\n\t continue;
\n\t }
\n\t if (ifnum != NI_LOCAL) { \/* \u6b64\u62a5\u4e0d\u662f\u672c\u673a\u4ea7\u751f\u7684*\/
\n\t if (cksum((WORD *)pip, IP_HLEN(pip))) { \/* \u8ba1\u7b97\u68c0\u9a8c\u548c*\/
\n\t IpInHdrErrors++;
\n\t freebuf(pep);
\n\t continue;
\n\t }
\n\t ipnet2h(pip);
\n\t pep->ep_order |= EPO_IP;
\n\t }
\n\t prt = rtget(pip->ip_dst, (ifnum == NI_LOCAL)); \/* \u9009\u62e9\u8def\u7531*\/<\/p>\n
\t if (prt == NULL) { \/* \u5982\u679c\u8def\u7531\u4e0d\u5b58\u5728*\/
\n\t if (gateway) { \/* \u5982\u7f51\u5173\u5b58\u5728\u53d1\u9001ICMP\u4e0d\u53ef\u8fbe*\/
\n\t iph2net(pip);
\n\t pep->ep_order &= ~EPO_IP;
\n\t icmp(ICT_DESTUR, ICC_NETUR,
\n\t pip->ip_src, pep, 0);
\n\t } else {
\n\t IpOutNoRoutes++;
\n\t freebuf(pep);
\n\t }
\n\t continue;
\n\t }
\n\t nonlocal = ifnum != NI_LOCAL && prt->rt_ifnum != NI_LOCAL; \/* \u4e0d\u662f\u672c\u5730\u5730\u5740*\/
\n\t if (!gateway && nonlocal) { \/* \u4e0d\u662f\u7f51\u5173\u4e5f\u4e0d\u662f\u672c\u5730\u5730\u5740*\/
\n\t IpInAddrErrors++;
\n\t freebuf(pep);
\n\t rtfree(prt);
\n\t continue;
\n\t }
\n\t if (nonlocal)
\n\t IpForwDatagrams++;
\n\t \/* \u5982\u679c\u6211\u4eec\u53d1\u4ef6\u4eba,\u586b\u5199\u5728\u6e90IP *\/<\/p>\n
\t if (ifnum == NI_LOCAL) { \/* \u5982\u679c\u7f51\u7edc\u63a5\u53e3\u4e3a\u672c\u5730*\/
\n\t if (pip->ip_src == ip_anyaddr)
\n\t if (prt->rt_ifnum == NI_LOCAL) \/* \u8def\u7531\u7684\u63a5\u53e3\u4e3a\u672c\u5730*\/
\n\t pip->ip_src = pip->ip_dst;
\n\t else
\n\t pip->ip_src =
\n\t nif[prt->rt_ifnum].ni_ip;
\n\t } else if (–(pip->ip_ttl) == 0 && \/* ttl \u4e3a\u96f6,\u4e14\u8def\u7531\u63a5\u53e3\u4e0d\u4e3a\u672c\u5730*\/
\n\t prt->rt_ifnum != NI_LOCAL) {
\n\t IpInHdrErrors++;
\n\t iph2net(pip);
\n\t pep->ep_order &= ~EPO_IP;
\n\t icmp(ICT_TIMEX, ICC_TIMEX, pip->ip_src, pep, 0); \/*\u53d1\u9001ICMP\u8d85\u65f6\u62a5\u6587*\/
\n\t rtfree(prt);
\n\t continue;
\n\t }
\n\t ipdbc(ifnum, pep, prt); \/* \u5904\u7406\u5b9a\u5411\u5e7f\u64ad *\/
\n\t ipredirect(pep, ifnum, prt); \/* \u505a\u91cd\u5b9a\u5411\uff0c\u5982\u679c\u9700\u8981\u7684\u8bdd*\/
\n\t if (prt->rt_metric != 0)
\n\t ipputp(prt->rt_ifnum, prt->rt_gw, pep);
\n\t else
\n\t ipputp(prt->rt_ifnum, pip->ip_dst, pep);
\n\t rtfree(prt);
\n\t }
\n\t}<\/p>\n
\tint ippid, gateway, bsdbrc;<\/p>\n
\t4.4 \u6821\u9a8c\u548c\u7684\u8ba1\u7b97<\/p>\n
\t\/* cksum.c – cksum *\/<\/p>\n
\t\/*————————————————————————
\n\t * cksum – Return 16-bit ones complement of 16-bit ones complement sum
\n\t *————————————————————————
\n\t *\/
\n\tunsigned short
\n\tcksum(buf, nbytes)
\n\tunsigned short *buf;
\n\tint nbytes;
\n\t{
\n\t unsigned long sum;
\n\t unsigned short tmp;
\n\t int nwords;<\/p>\n
\t nwords = nbytes \/ 2; \/* \u5c06\u5b57\u8282\u8f6c\u6210\u5b57,\u4e5f\u5c31\u662f16\u4e2a\u7684\u4e2a\u6570 *\/
\n\t for (sum=0; nwords>0; nwords–) \/* \u5c0616\u4f4d\u4e3a\u5355\u4f4d\u505a\u7d2f\u52a0*\/
\n\t sum += *buf++;
\n\t if (nbytes & 1) { \/* \u5982\u957f\u5ea6\u4e0d\u662f16\u4f4d\u7684\u500d\u6570\u5219\u8865\u9f50*\/
\n\t tmp = *(unsigned char *)buf;
\n\t sum += tmp;
\n\t }
\n\t sum = (sum >> 16) + (sum & 0xffff); \/* \u9ad8\u4f4d\u4f4e\u4f4d\u76f8\u52a0 *\/
\n\t sum += (sum >> 16); \/* \u4e0a\u4e00\u6b65\u6ea2\u51fa\u65f6\uff0c\u5c06\u6ea2\u51fa\u4f4d\u4e5f\u52a0\u5230sum\u4e2d *\/
\n\t return (unsigned short)~sum; \/* \u8fd4\u56desum\u7684\u53cd\u7801*\/
\n\t}<\/p>\n
\n\t4.5 \u5904\u7406\u5b9a\u5411\u5e7f\u64ad<\/p>\n
\t\u4e3b\u8981\u505a\u4e86\u4e24\u4ef6\u4e8b,\u590d\u5236\u4e00\u4e2a\u526f\u672c,\u7136\u540e\u6b63\u5e38\u53d1\u9001
\n\t\/* ipdbc.c – ipdbc *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h><\/p>\n
\tstruct route *rtget(IPaddr, Bool);<\/p>\n
\t\/*————————————————————————
\n\t * ipdbc – handle IP directed broadcast copying
\n\t *————————————————————————
\n\t *\/
\n\tvoid
\n\tipdbc(unsigned ifnum, struct ep *pep, struct route *prt)
\n\t{
\n\t struct ip *pip = (struct ip *)pep->ep_data;
\n\t struct ep *pep2;
\n\t struct route *prt2;
\n\t int len;<\/p>\n
\t if (prt->rt_ifnum != NI_LOCAL)
\n\t return; \/* \u4e0d\u662f\u6211\u4eec *\/
\n\t if (!isbrc(pip->ip_dst))
\n\t return; \/* \u4e0d\u662f\u5e7f\u64ad *\/<\/p>\n
\t prt2 = rtget(pip->ip_dst, RTF_LOCAL); \/* \u9009\u62e9\u4e00\u4e2a\u8def\u7531 *\/
\n\t if (prt2 == NULL)
\n\t return;
\n\t if (prt2->rt_ifnum == ifnum) { \/* \u6ca1\u6709\u9488\u5bf9\u63a5\u53e3 *\/
\n\t rtfree(prt2);
\n\t return;
\n\t }<\/p>\n
\t \/* \u5b9a\u5411\u5e7f\u64ad\uff0c\u5efa\u7acb\u4e00\u4e2a\u526f\u672c *\/<\/p>\n
\t \/* len = ether header + IP packet *\/<\/p>\n
\t len = EP_HLEN + pip->ip_len;
\n\t if (len > EP_MAXLEN) \/* \u4e3a\u526f\u672c\u5206\u914d\u7f13\u51b2\u533a*\/
\n\t pep2 = (struct ep *)getbuf(Net.lrgpool);
\n\t else
\n\t pep2 = (struct ep *)getbuf(Net.netpool);
\n\t if (pep2 == (struct ep *)SYSERR) {
\n\t rtfree(prt2);
\n\t return;
\n\t }
\n\t memcpy(pep2, pep, len); \/* \u590d\u5236\u526f\u672c*\/
\n\t \/* \u53d1\u9001\u4e00\u4efd\u62f7\u8d1d\u5230\u7f51\u7edc *\/<\/p>\n
\t ipputp(prt2->rt_ifnum, pip->ip_dst, pep2);
\n\t rtfree(prt2);<\/p>\n
\t return; \/* continue; "pep" goes locally in IP *\/
\n\t}<\/p>\n
\t4.6 \u8bc6\u522b\u4e00\u4e2a\u5e7f\u64ad\u5730\u5740<\/p>\n
\t\/* isbrc.c – isbrc *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <sleep.h>
\n\t#include <network.h><\/p>\n
\t\/*————————————————————————
\n\t * isbrc – Is "dest" a broadcast address?
\n\t *————————————————————————
\n\t *\/
\n\tBool
\n\tisbrc(IPaddr dest)
\n\t{
\n\t int inum;<\/p>\n
\t \/* \u6240\u6709\u76840\u548c\u51681\u7684\u662f\u5e7f\u64ad\u5730\u5740 *\/<\/p>\n
\t if (dest == ip_anyaddr || dest == ip_maskall) \/* \u5982\u679c\u4e3a\u51680 \u6216 \u51681 \u5219\u8fd4\u56de\u771f*\/
\n\t return TRUE;<\/p>\n
\t \/* \u68c0\u67e5\u771f\u6b63\u7684\u5e7f\u64ad\u5730\u5740\u548cBSD\u98ce\u683c\u7684\u7f51\u548c\u5b50\u7f51 *\/<\/p>\n
\t for (inum=0; inum < Net.nif; ++inum)
\n\t if (dest == nif[inum].ni_brc ||
\n\t dest == nif[inum].ni_nbrc ||
\n\t dest == nif[inum].ni_subnet ||
\n\t dest == nif[inum].ni_net)
\n\t return TRUE;<\/p>\n
\t return FALSE;
\n\t}<\/p>\n
\n\t5. IP\u9996\u90e8\u4e2d\u7684\u5b57\u8282\u987a\u5e8f<\/p>\n
\t\/* iph2net.c – iph2net *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h><\/p>\n
\t\/*————————————————————————
\n\t * iph2net – iph2net – \u8f6c\u6362\u6210\u4e00\u4e2aIP\u6570\u636e\u5305\u5934\u4ece\u4e3b\u673a\u5230\u7f51\u7edc\u5b57\u8282\u987a\u5e8f
\n\t *————————————————————————
\n\t *\/
\n\tstruct ip *
\n\tiph2net(struct ip *pip)
\n\t{
\n\t \/* \u6ce8\uff1a\u4e0d\u5305\u62ecIP\u9009\u9879 *\/<\/p>\n
\t pip->ip_len = hs2net(pip->ip_len);
\n\t pip->ip_id = hs2net(pip->ip_id);
\n\t pip->ip_fragoff = hs2net(pip->ip_fragoff);
\n\t return pip;
\n\t}<\/p>\n
\n\t\/* ipnet2h.c – ipnet2h *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h><\/p>\n
\t\/*————————————————————————
\n\t * ipnet2h – \u8f6c\u6362\u6210\u4e00\u4e2aIP\u6570\u636e\u5305\u5934\u4ece\u7f51\u7edc\u5230\u4e3b\u673a\u5b57\u8282\u987a\u5e8f
\n\t *————————————————————————
\n\t *\/
\n\tstruct ip *
\n\tipnet2h(struct ip *pip)
\n\t{
\n\t \/* \u6ce8\uff1a\u4e0d\u5305\u62ecIP\u9009\u9879 *\/<\/p>\n
\t pip->ip_len = net2hs(pip->ip_len);
\n\t pip->ip_id = net2hs(pip->ip_id);
\n\t pip->ip_fragoff = net2hs(pip->ip_fragoff);
\n\t return pip;
\n\t}<\/p>\n
\n\t6. \u5411IP\u53d1\u9001\u6570\u636e\u62a5<\/p>\n
\t6.1 \u53d1\u9001\u672c\u5730\u751f\u6210\u7684\u6570\u636e\u62a5 <\/p>\n
\t\/* ipsend.c – ipsend *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h>
\n\t#include <proc.h><\/p>\n
\tstatic ipackid = 1; \/* \u9759\u6001\u53d8\u91cf \u6807\u8bc6*\/<\/p>\n
\t\/*————————————————————————
\n\t * ipsend – \u53d1\u9001\u4e00\u4e2aIP\u6570\u636e\u62a5\u5230\u6307\u5b9a\u5730\u5740
\n\t *————————————————————————
\n\t *\/
\n\tint
\n\tipsend(IPaddr faddr, struct ep *pep, unsigned datalen,
\n\t u_char proto, u_char ptos, u_char ttl)
\n\t{
\n\t struct ip *pip = (struct ip *) pep->ep_data;<\/p>\n
\t pep->ep_type = EPT_IP; \/* \u7c7b\u578b\u4e3a\u7f51\u9645\u534f\u8bae*\/
\n\t pep->ep_order |= EPO_IP|EPO_NET; \/* \u7f51\u7edc\u5c42 \u534f\u8bae\u7b49\u7ea7\u4e3a1*\/
\n\t pip->ip_verlen = (IP_VERSION<<4) | IP_MINHLEN; \/* \u534f\u8bae\u7248\u672c \u6700\u5c0f\u7684IP\u5934\u957f\u5ea6*\/
\n\t pip->ip_tos = ptos; \/* \u8bbe\u7f6e\u670d\u52a1\u7c7b\u578b\u4e0e\u4f18\u5148\u7ea7*\/
\n\t pip->ip_len = datalen+IP_HLEN(pip); \/* IP\u5206\u7ec4\u7684\u957f\u5ea6*\/
\n\t pip->ip_id = ipackid++; \/* \u5206\u7ec4\u7684\u6807\u8bc6*\/
\n\t pip->ip_fragoff = 0; \/* \u5206\u7247\u7684\u504f\u79fb*\/
\n\t pip->ip_ttl = ttl; \/* \u751f\u5b58\u65f6\u95f4*\/
\n\t pip->ip_proto = proto; \/* \u534f\u8bae\u7c7b\u578b*\/
\n\t pip->ip_dst = faddr; \/* \u76ee\u6807\u5730\u5740*\/<\/p>\n
\t \/*
\n\t * \u7279\u6b8a\u60c5\u51b5\u7684ICMP\u534f\u8bae\uff0c\u56e0\u6b64\u6e90\u5339\u914d\u76ee\u7684\u5730
\n\t * on multi-homed hosts. \u591a\u7a74\u4e3b\u673a??
\n\t *\/
\n\t if (pip->ip_proto != IPT_ICMP) \/* \u4e0d\u662fICMP\u5206\u7ec4*\/
\n\t pip->ip_src = ip_anyaddr; \/* IP\u7684\u6e90\u5730\u5740\u4e3a\u4efb\u610f\u5730\u5740*\/<\/p>\n
\t if (enq(nif[NI_LOCAL].ni_ipinq, pep, 0) < 0) { \/* \u5c06\u5206\u7ec4\u653e\u5165\u672c\u5730\u4e3b\u673a\u63a5\u53e3\u961f\u5217\u4e2d*\/
\n\t freebuf(pep);
\n\t IpOutDiscards++;
\n\t }
\n\t send(ippid, NI_LOCAL); \/* IP\u6570\u636e\u62a5\u963b\u585e\u5e76\u7b49\u5f85\uff0c\u53d1\u9001\u62a5\u6587\u7ed9IP\u8fdb\u7a0b*\/
\n\t IpOutRequests++;
\n\t return OK;
\n\t}
\n\t\/* \u7279\u6b8a\u7684IP\u5730\u5740 *\/<\/p>\n
\tIPaddr ip_anyaddr = 0;
\n\t#if BYTE_ORDER == LITTLE_ENDIAN
\n\tIPaddr ip_loopback = 0x0100007F; \/* 127.0.0.1 *\/
\n\t#else \/* BYTE_ORDER *\/
\n\tIPaddr ip_loopback = 0x7F000001; \/* 127.0.0.1 *\/
\n\t#endif \/* BYTE_ORDER *\/<\/p>\n
\n\t6.2 \u53d1\u9001\u4f20\u5165\u6570\u636e\u62a5<\/p>\n
\t\/* ip_in.c – ip_in *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <network.h>
\n\t#include <proc.h><\/p>\n
\t\/*————————————————————————
\n\t * ip_in – IP input function
\n\t *————————————————————————
\n\t *\/
\n\tint
\n\tip_in(struct netif *pni, struct ep *pep)
\n\t{
\n\t struct ip *pip = (struct ip *)pep->ep_data;<\/p>\n
\t IpInReceives++;
\n\t if (enq(pni->ni_ipinq, pep, pip->ip_tos & IP_PREC) < 0) {
\n\t IpInDiscards++; \/* \u5982\u961f\u5217\u6ee1\u5219\u8bb0\u5f55\u6ea2\u51fa\u5dee\u9519\u5e76\u4e22\u5219\u62a5\u6587*\/
\n\t freebuf(pep);
\n\t }
\n\t send(ippid, (pni-&nif[0])); \/* \u5411IP\u8fdb\u7a0b\u53d1\u9001\u6d88\u606f*\/
\n\t return OK;
\n\t}<\/p>\n
\t7. \u8868\u683c\u7684\u7ef4\u62a4<\/p>\n
\t\/* slowtimer.c – slowtimer *\/<\/p>\n
\t#include <conf.h>
\n\t#include <kernel.h>
\n\t#include <proc.h>
\n\t#include <sleep.h>
\n\t#include <date.h>
\n\t#include <network.h><\/p>\n
\t#define STGRAN 1 \/* \u5b9a\u65f6\u5668\u7c92\u5ea6\uff08\u5ef6\u8fdf\u79d2\uff09 *\/<\/p>\n
\tvoid arptimer(unsigned), ipftimer(unsigned), rttimer(unsigned);
\n\t#ifdef OSPF
\n\tvoid ospftimer(unsigned);
\n\t#endif \/*OSPF*\/<\/p>\n
\t\/*————————————————————————
\n\t * slowtimer – \u5904\u7406\u957f\u671f\u5b9a\u671f\u7ef4\u62a4\u7f51\u7edc\u8868
\n\t *————————————————————————
\n\t *\/
\n\tPROCESS
\n\tslowtimer(void)
\n\t{
\n\t unsigned long lasttime, now; \/* prev and current times (secs)*\/
\n\t int delay; \/* \u51e0\u79d2\u949f\u5185\u5b9e\u9645\u5ef6\u8fdf *\/<\/p>\n
\t signal(Net.sema);<\/p>\n
\t gettime(&lasttime);
\n\t while (1) {
\n\t sleep(STGRAN); \/* \u5ef6\u65f6*\/
\n\t gettime(&now);
\n\t delay = now – lasttime;
\n\t if (delay <= 0 || delay > 4*STGRAN)
\n\t delay = STGRAN; \/* \u65f6\u949f\u590d\u4f4d-likely clock reset *\/
\n\t lasttime = now;
\n\t arptimer(delay);
\n\t ipftimer(delay);
\n\t rttimer(delay);
\n\t#ifdef OSPF
\n\t ospftimer(delay);
\n\t#endif \/* OSPF *\/
\n\t }
\n\t}
\n\t <\/p>\n","protected":false},"excerpt":{"rendered":"
1.\u4e2d\u5fc3\u73af\u8282 IP\u662f\u6574\u4e2a\u534f\u8bae\u8f6f\u4ef6\u7684\u4e2d\u5fc3\u73af\u8282,\u4e0d\u8981\u628aIP\u8f6f\u4ef6\u7b80\u5355\u7684\u5206\u5272\u6210\u8f93\u5165\u548c\u8f93\u51fa\u4e24\u90e8\u5206,\u56e0\u4e3a\u8f93\u5165\u548c\u8f93\u51fa\u7684\u754c\u9650\u5f88 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,5,14],"tags":[],"class_list":["post-596","post","type-post","status-publish","format-standard","hentry","category-linux","category-linux-c","category-14"],"_links":{"self":[{"href":"https:\/\/www.kumouse.com\/index.php?rest_route=\/wp\/v2\/posts\/596","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.kumouse.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.kumouse.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.kumouse.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.kumouse.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=596"}],"version-history":[{"count":0,"href":"https:\/\/www.kumouse.com\/index.php?rest_route=\/wp\/v2\/posts\/596\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.kumouse.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=596"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.kumouse.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=596"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.kumouse.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=596"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}