学习Linux-4.12内核网路协议栈（1.6）——协议栈的初始化(inet_init实现过程)

太过爱你忘了你带给我的痛 2022-06-13 14:45 614阅读 0赞

这篇文章主要分析inet\_init（）函数的实现过程：

1796 static int __init inet_init(void)
    1797 {
    1798     struct inet_protosw *q;
    1799     struct list_head *r;
    1800     int rc = -EINVAL;
    1801
    1802     sock_skb_cb_check_size(sizeof(struct inet_skb_parm));
    1803
    1804     rc = proto_register(&tcp_prot, 1);
    1805     if (rc)
    1806         goto out;
    1807
    1808     rc = proto_register(&udp_prot, 1);
    1809     if (rc)
    1810         goto out_unregister_tcp_proto;
    1811
    1812     rc = proto_register(&raw_prot, 1);
    1813     if (rc)
    1814         goto out_unregister_udp_proto;
    1815
    1816     rc = proto_register(&ping_prot, 1);
    1817     if (rc)
    1818         goto out_unregister_raw_proto;
    1820     /*
    1821      *  Tell SOCKET that we are alive...
    1822      */
    1823
    1824     (void)sock_register(&inet_family_ops);
    1825
    1826 #ifdef CONFIG_SYSCTL
    1827     ip_static_sysctl_init();
    1828 #endif
    1829
    1830     /*
    1831      *  Add all the base protocols.
    1832      */
    1833
    1834     if (inet_add_protocol(&icmp_protocol, IPPROTO_ICMP) < 0)
    1835         pr_crit("%s: Cannot add ICMP protocol\n", __func__);
    1836     if (inet_add_protocol(&udp_protocol, IPPROTO_UDP) < 0)
    1837         pr_crit("%s: Cannot add UDP protocol\n", __func__);
    1838     if (inet_add_protocol(&tcp_protocol, IPPROTO_TCP) < 0)
    1839         pr_crit("%s: Cannot add TCP protocol\n", __func__);
    1840 #ifdef CONFIG_IP_MULTICAST
    1841     if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0)
    1842         pr_crit("%s: Cannot add IGMP protocol\n", __func__);
    1843 #endif
    1844
    1845     /* Register the socket-side information for inet_create. */
    1846     for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r)
    1847         INIT_LIST_HEAD(r);
    1848
    1849     for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q)
    1850         inet_register_protosw(q);
    1852     /*
    1853      *  Set the ARP module up
    1854      */
    1855
    1856     arp_init();
    1857
    1858     /*
    1859      *  Set the IP module up
    1860      */
    1861
    1862     ip_init();
    1863
    1864     /* Setup TCP slab cache for open requests. */
    1865     tcp_init();
    1866
    1867     /* Setup UDP memory threshold */
    1868     udp_init();
    1869
    1870     /* Add UDP-Lite (RFC 3828) */
    1871     udplite4_register();
    1872
    1873     ping_init();
    1874
    1875     /*
    1876      *  Set the ICMP layer up
    1877      */
    1878
    1879     if (icmp_init() < 0)
    1880         panic("Failed to create the ICMP control socket.\n");
    1881
    1882     /*
    1883      *  Initialise the multicast router
    1884      */
    1885 #if defined(CONFIG_IP_MROUTE)
    1886     if (ip_mr_init())
    1887         pr_crit("%s: Cannot init ipv4 mroute\n", __func__);
    1888 #endif
    1889
    1890     if (init_inet_pernet_ops())
    1891         pr_crit("%s: Cannot init ipv4 inet pernet ops\n", __func__);
    1892     /*
    1893      *  Initialise per-cpu ipv4 mibs
    1894      */
    1895
    1896     if (init_ipv4_mibs())
    1897         pr_crit("%s: Cannot init ipv4 mibs\n", __func__);
    1898
    1899     ipv4_proc_init();
    1900
    1901     ipfrag_init();
    1902
    1903     dev_add_pack(&ip_packet_type);
    1904
    1905     ip_tunnel_core_init();
    1906
    1907     rc = 0;
    1908 out:
    1909     return rc;
    1910 out_unregister_raw_proto:
    1911     proto_unregister(&raw_prot);
    1912 out_unregister_udp_proto:
    1913     proto_unregister(&udp_prot);
    1914 out_unregister_tcp_proto:
    1915     proto_unregister(&tcp_prot);
    1916     goto out;
    1917 }
    1918
    1919 fs_initcall(inet_init);

其他函数在前面的都介绍过了，这篇文章我们主要介绍下面几个函数：

1856     arp_init();
    1857
    1858     /*
    1859      *  Set the IP module up
    1860      */
    1861
    1862     ip_init();
    1863
    1864     /* Setup TCP slab cache for open requests. */
    1865     tcp_init();
    1866
    1867     /* Setup UDP memory threshold */
    1868     udp_init();
    1869
    1870     /* Add UDP-Lite (RFC 3828) */
    1871     udplite4_register();
    1872
    1873     ping_init();
    1874
    1875     /*
    1876      *  Set the ICMP layer up
    1877      */
    1878
    1879     if (icmp_init() < 0)
    1880         panic("Failed to create the ICMP control socket.\n");
    1881
    1882     /*
    1883      *  Initialise the multicast router
    1884      */
    1885 #if defined(CONFIG_IP_MROUTE)
    1886     if (ip_mr_init())
    1887         pr_crit("%s: Cannot init ipv4 mroute\n", __func__);
    1888 #endif
    1889
    1890     if (init_inet_pernet_ops())
    1891         pr_crit("%s: Cannot init ipv4 inet pernet ops\n", __func__);
    1892     /*
    1893      *  Initialise per-cpu ipv4 mibs
    1894      */
    1895
    1896     if (init_ipv4_mibs())
    1897         pr_crit("%s: Cannot init ipv4 mibs\n", __func__);
    1898
    1899     ipv4_proc_init();
    1900
    1901     ipfrag_init();
    1902
    1903     dev_add_pack(&ip_packet_type);
    1904
    1905     ip_tunnel_core_init();

## 1. arp\_init() ##

1281 void __init arp_init(void)
    1282 {
    1283     neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
    1284
    1285     dev_add_pack(&arp_packet_type);
    1286     arp_proc_init();
    1287 #ifdef CONFIG_SYSCTL
    1288     neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
    1289 #endif
    1290     register_netdevice_notifier(&arp_netdev_notifier);
    1291 }

这个函数比较简单，就是将arp的协议类型添加到ptype\_base\[\]里面，当IP层收到arp包的时候调用arp\_rcv()函数进行处理。

同时也完成/proc/net/arp文件的初始化。

## 2. ip\_init() ##

//ip子系统初始化  
    //调用路径inet_init->ip_init  
    //包括路由子系统的初始化，inet_peer缓存的初始化  
    void __init ip_init(void)  
    {   
        ip_rt_init(); //路由子系统初始化  
        inet_initpeers();//inet_peer缓存  
    #if defined(CONFIG_IP_MULTICAST)
       igmp_mc_init();
    #endif
    
    
    }  
      
    //调用路径ip_init->inet_initpeers  
    //inet_peer缓存初始化  
    //  1.每一个与linux通过inet协议交换过数据的主机，都会被认为是一个ip peer，linux为每个peer分配一个inet_peer结构。  
    //  2.inet_peer的主要目的，使不同ip使用不同的ip id生成器。  
    //  3.系统中所有的inet_peer实例组织成一课avl树，方便查找。  
    1.2 void __init inet_initpeers(void)  
    {  
        struct sysinfo si;  
      
        //获取系统内存信息  
        si_meminfo(&si);  
        //系统中inet_peer数量的阀值  
        if (si.totalram <= (32768*1024)/PAGE_SIZE)  
            inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */  
        if (si.totalram <= (16384*1024)/PAGE_SIZE)  
            inet_peer_threshold >>= 1; /* about 512KB */  
        if (si.totalram <= (8192*1024)/PAGE_SIZE)  
            inet_peer_threshold >>= 2; /* about 128KB */  
        //inet_peer SLAB cache  
        peer_cachep = kmem_cache_create("inet_peer_cache",  
                sizeof(struct inet_peer),  
                0, SLAB_HWCACHE_ALIGN|SLAB_PANIC,  
                NULL);  
        //垃圾回收  
        peer_periodic_timer.expires = jiffies  
            + net_random() % inet_peer_gc_maxtime  
            + inet_peer_gc_maxtime;  
        add_timer(&peer_periodic_timer);  
    }

## 3. tcp\_init() ##

tcp的初始化内容比较多，后面单独讲

## 4. udp\_init（） ##

2653 void __init udp_init(void)
    2654 {
    2655     unsigned long limit;
    2656     unsigned int i;
    2657
    2658     udp_table_init(&udp_table, "UDP");
    2659     limit = nr_free_buffer_pages() / 8;
    2660     limit = max(limit, 128UL);
    2661     sysctl_udp_mem[0] = limit / 4 * 3;
    2662     sysctl_udp_mem[1] = limit;
    2663     sysctl_udp_mem[2] = sysctl_udp_mem[0] * 2;
    2664
    2665     sysctl_udp_rmem_min = SK_MEM_QUANTUM;
    2666     sysctl_udp_wmem_min = SK_MEM_QUANTUM;
    2667
    2668     /* 16 spinlocks per cpu */
    2669     udp_busylocks_log = ilog2(nr_cpu_ids) + 4;
    2670     udp_busylocks = kmalloc(sizeof(spinlock_t) << udp_busylocks_log,
    2671                 GFP_KERNEL);
    2672     if (!udp_busylocks)
    2673         panic("UDP: failed to alloc udp_busylocks\n");
    2674     for (i = 0; i < (1U << udp_busylocks_log); i++)
    2675         spin_lock_init(udp_busylocks + i);
    2676 }

这里主要完成udp\_table的初始化：

67 /**
     68  *  struct udp_table - UDP table
     69  *
     70  *  @hash:  hash table, sockets are hashed on (local port)
     71  *  @hash2: hash table, sockets are hashed on (local port, local address)
     72  *  @mask:  number of slots in hash tables, minus 1
     73  *  @log:   log2(number of slots in hash table)
     74  */ 
     75 struct udp_table {
     76     struct udp_hslot    *hash;
     77     struct udp_hslot    *hash2;
     78     unsigned int        mask;
     79     unsigned int        log;
     80 };

这个函数主要创建了两个hash表，用于串联本地套接字对应的端口号

## 5. icmp\_init（）    ##

1252 int __init icmp_init(void)
    1253 {
    1254     return register_pernet_subsys(&icmp_sk_ops);
    1255 }

该函数的主要作用是将一个网络协议模块添加到每一个网络命令空间中，然后再执行其ops->init程序进行初始化，一般其ops->init会在其对应的proc目录下，生成一个网络协议模块对应的proc文件或proc目录，并执行一些协议初始化相关的函数。

1247 static struct pernet_operations __net_initdata icmp_sk_ops = {
    1248        .init = icmp_sk_init,
    1249        .exit = icmp_sk_exit,
    1250 };

1185 static int __net_init icmp_sk_init(struct net *net)
    1186 {
    1187     int i, err;
    1188
    1189     net->ipv4.icmp_sk = alloc_percpu(struct sock *);
    1190     if (!net->ipv4.icmp_sk)
    1191         return -ENOMEM;
    1192
    1193     for_each_possible_cpu(i) {
    1194         struct sock *sk;
    1195
    1196         err = inet_ctl_sock_create(&sk, PF_INET,
    1197                        SOCK_RAW, IPPROTO_ICMP, net);
    1198         if (err < 0)
    1199             goto fail;
    1200
    1201         *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk;
    1202
    1203         /* Enough space for 2 64K ICMP packets, including
    1204          * sk_buff/skb_shared_info struct overhead.
    1205          */
    1206         sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
    1207
    1208         /*
    1209          * Speedup sock_wfree()
    1210          */
    1211         sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
    1212         inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
    1213     }
    1214
    1215     /* Control parameters for ECHO replies. */
    1216     net->ipv4.sysctl_icmp_echo_ignore_all = 0;
    1217     net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
    1218
    1219     /* Control parameter - ignore bogus broadcast responses? */
    1220     net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
    1221
    1222     /*
    1223      *  Configurable global rate limit.
    1224      *
    1225      *  ratelimit defines tokens/packet consumed for dst->rate_token
    1226      *  bucket ratemask defines which icmp types are ratelimited by
    1227      *  setting it's bit position.
    1228      *
    1229      *  default:
    1230      *  dest unreachable (3), source quench (4),
    1231      *  time exceeded (11), parameter problem (12)
    1232      */
    1233
    1234     net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
    1235     net->ipv4.sysctl_icmp_ratemask = 0x1818;
    1236     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
    1237
    1238     return 0;
    1239
    1240 fail:
    1241     for_each_possible_cpu(i)
    1242         inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i));
    1243     free_percpu(net->ipv4.icmp_sk);
    1244     return err;
    1245 }

[http://blog.csdn.net/lickylin/article/details/24208463][http_blog.csdn.net_lickylin_article_details_24208463]

## 6.init\_inet\_pernet\_ops()    ##

它最后调用inet\_init\_net(struct net \*net)完成以下网路命名空间的初始化，每一个网络设备都会有一个网络命名空间，比如eth1， ath0等，可以[查看这里了解。][Link 1]

## 7. init\_ipv4\_mibs()    ##

前面说了，每一个网络接口都对应着一个网络命名空间，这些网路空间串联在一个由”struct net”对象组成的结构体中，该函数完成这些空间数据统计的一些信息初始化。

static __net_init int ipv4_mib_init_net(struct net *net)
    {
            int i;
    
            net->mib.tcp_statistics = alloc_percpu(struct tcp_mib);
            if (!net->mib.tcp_statistics)
                    goto err_tcp_mib;
            net->mib.ip_statistics = alloc_percpu(struct ipstats_mib);
            if (!net->mib.ip_statistics)
                    goto err_ip_mib;
    
            for_each_possible_cpu(i) {
                    struct ipstats_mib *af_inet_stats;
                    af_inet_stats = per_cpu_ptr(net->mib.ip_statistics, i);
                    u64_stats_init(&af_inet_stats->syncp);
            }
    
            net->mib.net_statistics = alloc_percpu(struct linux_mib);
            if (!net->mib.net_statistics)
                    goto err_net_mib;
            net->mib.udp_statistics = alloc_percpu(struct udp_mib);
            if (!net->mib.udp_statistics)
                    goto err_udp_mib;
            net->mib.udplite_statistics = alloc_percpu(struct udp_mib);
            if (!net->mib.udplite_statistics)
                    goto err_udplite_mib;
            net->mib.icmp_statistics = alloc_percpu(struct icmp_mib);
            if (!net->mib.icmp_statistics)
                    goto err_icmp_mib;
            net->mib.icmpmsg_statistics = kzalloc(sizeof(struct icmpmsg_mib),
                                                  GFP_KERNEL);
            if (!net->mib.icmpmsg_statistics)
                    goto err_icmpmsg_mib;
    
            tcp_mib_init(net);

## 8. ipfrag\_init（） ##

IP分片的初始化，其中指定了对应动作所调用的函数

void __init ipfrag_init(void)
    {
            ip4_frags_ctl_register();
            register_pernet_subsys(&ip4_frags_ops);
            ip4_frags.hashfn = ip4_hashfn;
            ip4_frags.constructor = ip4_frag_init;
            ip4_frags.destructor = ip4_frag_free;
            ip4_frags.qsize = sizeof(struct ipq);
            ip4_frags.match = ip4_frag_match;
            ip4_frags.frag_expire = ip_expire;
            ip4_frags.frags_cache_name = ip_frag_cache_name;
            if (inet_frags_init(&ip4_frags))
                    panic("IP: failed to allocate ip4_frags cache\n");
    }

## 9. ipv4\_proc\_init() ##

在proc的ipv4目录下，会根据不同的协议创建不同的文件

static int __init ipv4_proc_init(void)
    {
            int rc = 0;
    
            if (raw_proc_init())
                    goto out_raw;
            if (tcp4_proc_init())
                    goto out_tcp;
            if (udp4_proc_init())
                    goto out_udp;
            if (ping_proc_init())
                    goto out_ping;
            if (ip_misc_proc_init())
                    goto out_misc;

root:/proc/213/net\# cat tcp  
sl local\_address rem\_address st tx\_queue rx\_queue tr tm->when retrnsmt uid timeout inode  
0: 00000000:8240 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 18057 1 d9aa0000 100 0 0 10 0  
1: FA01A8C0:C000 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 10027 1 d9828000 100 0 0 10 0  
2: 00000000:4E25 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 18624 1 d86b8000 100 0 0 10 0  
3: 00000000:0D05 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 3566 1 de690500 100 0 0 10 0  
4: 0100007F:1E6B 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 16883 1 d9828500 100 0 0 10 0  
5: 00000000:0050 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 3548 1 de690000 100 0 0 10 0  
6: 00000000:15B3 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 10551287 1 d86bc600 100 0 0 10 0  
7: 00000000:0277 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 18632 1 d86b8500 100 0 0 10 0  
8: 0100007F:DAEA 0100007F:0050 06 00000000:00000000 03:00000640 00000000 0 0 0 3 d86c7d80  
9: FA01A8C0:A668 0A01A8C0:0B35 06 00000000:00000000 03:000011B2 00000000 0 0 0 3 de52c000  
10: FA01A8C0:A664 0A01A8C0:0B35 06 00000000:00000000 03:0000107F 00000000 0 0 0 3 de52ca80  
11: FA01A8C0:A669 0A01A8C0:0B35 06 00000000:00000000 03:000011B1 00000000 0 0 0 3 de52c180  
12: FA01A8C0:A66A 0A01A8C0:0B35 06 00000000:00000000 03:000011B1 00000000 0 0 0 3 de52c480  
13: FA01A8C0:A670 0A01A8C0:0B35 06 00000000:00000000 03:000014B9 00000000 0 0 0 3 d9fb3cc0  
14: FA01A8C0:A64B 0A01A8C0:0B35 06 00000000:00000000 03:00000216 00000000 0 0 0 3 d9fb3e40

也许你会问路径里面的213是什么，应该是不同的name space 吧

[http_blog.csdn.net_lickylin_article_details_24208463]: http://blog.csdn.net/lickylin/article/details/24208463
[Link 1]: http://weiguozhihui.blog.51cto.com/3060615/1584610