Linux內核--網絡協議棧深入分析(四)--套接字內核初始化和創建過程

本文分析基於Linux Kernel 3.2.1

更多請查看 Linux內核--網絡內核實現分析

1、系統初始化過程中會調用sock_init函數進行套接字的初始化，主要是進行緩存的初始化

1. static int __init sock_init(void)
2. {
3. int err;
5. /*
6. * 初始化.sock緩存
7. */
9. sk_init();
11. /*
12. * 初始化sk_buff緩存
13. */
14. skb_init();
16. /*
17. * 初始化協議模塊緩存
18. */
20. init_inodecache();
21. //注冊文件系統類型
22. err = register_filesystem(&sock_fs_type);
23. if (err)
24. goto out_fs;
25. sock_mnt = kern_mount(&sock_fs_type);
26. if (IS_ERR(sock_mnt)) {
27. err = PTR_ERR(sock_mnt);
28. goto out_mount;
29. }
31. /* The real protocol initialization is performed in later initcalls.
32. */
34. #ifdef CONFIG_NETFILTER
35. netfilter_init();
36. #endif
38. #ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
39. skb_timestamping_init();
40. #endif
42. out:
43. return err;
45. out_mount:
46. unregister_filesystem(&sock_fs_type);
47. out_fs:
48. goto out;
49. }

2、INET協議族的初始化函數

1. static int __init inet_init(void)
2. {
3. struct sk_buff *dummy_skb;
4. struct inet_protosw *q;
5. struct list_head *r;
6. int rc = -EINVAL;
8. BUILD_BUG_ON(sizeof(struct inet_skb_parm) > sizeof(dummy_skb->cb));
10. sysctl_local_reserved_ports = kzalloc(65536 / 8, GFP_KERNEL);
11. if (!sysctl_local_reserved_ports)
12. goto out;
14. //下面注冊傳輸層協議操作集
15. rc = proto_register(&tcp_prot, 1);
16. if (rc)
17. goto out_free_reserved_ports;
19. rc = proto_register(&udp_prot, 1);
20. if (rc)
21. goto out_unregister_tcp_proto;
23. rc = proto_register(&raw_prot, 1);
24. if (rc)
25. goto out_unregister_udp_proto;
27. rc = proto_register(&ping_prot, 1);
28. if (rc)
29. goto out_unregister_raw_proto;
31. //注冊INET協議族的handler
32. (void)sock_register(&inet_family_ops);
34. #ifdef CONFIG_SYSCTL
35. ip_static_sysctl_init();
36. #endif
38. /*
39. * Add all the base protocols.
40. */
41. //將INET協議族協議數據包接收函數添加到系統中
42. if (inet_add_protocol(&icmp_protocol, IPPROTO_ICMP) < 0)
43. printk(KERN_CRIT "inet_init: Cannot add ICMP protocol\n");
44. if (inet_add_protocol(&udp_protocol, IPPROTO_UDP) < 0)
45. printk(KERN_CRIT "inet_init: Cannot add UDP protocol\n");
46. if (inet_add_protocol(&tcp_protocol, IPPROTO_TCP) < 0)
47. printk(KERN_CRIT "inet_init: Cannot add TCP protocol\n");
48. #ifdef CONFIG_IP_MULTICAST
49. if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0)
50. printk(KERN_CRIT "inet_init: Cannot add IGMP protocol\n");
51. #endif
53. /* Register the socket-side information for inet_create. */
54. for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r)
55. INIT_LIST_HEAD(r);
56. //將inetsw_array中的元素按套接字類型注冊到inetsw鏈表數組中
57. for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q)
58. inet_register_protosw(q);
60. /*
61. * Set the ARP module up
62. */
64. arp_init();
66. /*
67. * Set the IP module up
68. */
70. ip_init();
72. tcp_v4_init();
74. /* Setup TCP slab cache for open requests. */
75. tcp_init();
77. /* Setup UDP memory threshold */
78. udp_init();
80. /* Add UDP-Lite (RFC 3828) */
81. udplite4_register();
83. ping_init();
85. /*
86. * Set the ICMP layer up
87. */
89. if (icmp_init() < 0)
90. panic("Failed to create the ICMP control socket.\n");
92. /*
93. * Initialise the multicast router
94. */
95. #if defined(CONFIG_IP_MROUTE)
96. if (ip_mr_init())
97. printk(KERN_CRIT "inet_init: Cannot init ipv4 mroute\n");
98. #endif
99. /*
100. * Initialise per-cpu ipv4 mibs
101. */
103. if (init_ipv4_mibs())
104. printk(KERN_CRIT "inet_init: Cannot init ipv4 mibs\n");
106. ipv4_proc_init();
108. ipfrag_init();
110. dev_add_pack(&ip_packet_type);
112. rc = 0;
113. out:
114. return rc;
115. out_unregister_raw_proto:
116. proto_unregister(&raw_prot);
117. out_unregister_udp_proto:
118. proto_unregister(&udp_prot);
119. out_unregister_tcp_proto:
120. proto_unregister(&tcp_prot);
121. out_free_reserved_ports:
122. kfree(sysctl_local_reserved_ports);
123. goto out;
124. }