Linux内核--网络栈实现分析（二）--数据包的传递过程--转

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1. ?
3. ??
5. {??
6. h.iph;??
7. ?????sock?*raw_sk=NULL;??
9. ????unsigned??flag?=?0;??
11. ?????inet_protocol?*ipprot;??
13. ??
15. ?????is_frag=0;??
17. ?????err;??
19. ??
21. ??
23. ?
25. ??
26. ip_hdr?=?iph;??
27. ??
29. ?
31. ?
33. ?
35. ??
37. ?????(skb->len<(?iphdr)?||?iph->ihl<5?||?iph->version?!=?4?||??
38. lentot_len)?||?ip_fast_csum((unsigned??*)iph,?iph->ihl)?!=0)??
39. ????{??
41. ????????kfree_skb(skb,?FREE_WRITE);??
43. ????}??
45. ?????
47. ??
49. ??
51. ?????((err=ip_fw_chk(iph,dev,ip_fw_blk_chain,ip_fw_blk_policy,?0))!=1)??
53. ????????(err==-1)??
55. ????????kfree_skb(skb,?FREE_WRITE);??
57. ????}??
59. ??
61. ?????
63. ?
65. ??
66. len=ntohs(iph->tot_len);??
67. ??
69. ?
71. ??
73. ?????(iph->ihl?!=?5)??
75. ????????memset((?*)?&opt,?(opt));??
77. ?????????????0;??
79. ????}??
81. ?????
83. ??
85. ????(iph->frag_off)??
87. ?????????(iph->frag_off?&?0x0020)??
89. ?????????
91. ??
93. ?????????(ntohs(iph->frag_off)?&?0x1fff)??
95. ????}??
97. ?????
99. ?
101. ?
103. ?
105. ?
107. ??
109. ?????(?iph->daddr?!=?skb->dev->pa_addr?&&?(brd?=?ip_chk_addr(iph->daddr))?==?0)??
111. ?????????
113. ??
115. ????????(skb->pkt_type!=PACKET_HOST?||?brd==IS_BROADCAST)??
117. ????????????kfree_skb(skb,FREE_WRITE);??
119. ????????}??
121. ?????????
123. ??
125. ??
127. ??
129. saddr,iph->daddr);*/??
131. ??
133. ?
135. ??
137. ????????kfree_skb(skb,?FREE_WRITE);??
139. ????}??
141. ??
143. ????(brd==IS_MULTICAST?&&?iph->daddr!=IGMP_ALL_HOSTS?&&?!(dev->flags&IFF_LOOPBACK))??
145. ?????????
147. ??
148. ip_mc_list;??
149. ??????????
151. ????????????(ip_mc==NULL)??
153. ????????????????kfree_skb(skb,?FREE_WRITE);??
155. ????????????}??
156. multiaddr==iph->daddr)??
157. ????????????????;??
158. next;??
159. ????????}??
161. ????}??
163. ?????
165. ??
167. ??
169. ??
171. ?????
173. ??
175. ????(is_frag)??
177. ??????????
179. ????????(skb==NULL)??
181. ????????skb->dev?=?dev;??
182. h.iph;??
183. ????}??
185. ???????????
187. ?????
189. ??
191. ????skb->ip_hdr?=?iph;??
192. h.raw?+=?iph->ihl*4;??
193. ??????
195. ?
197. ???????
198. protocol?&?(SOCK_ARRAY_SIZE-1);??
199. ??????
201. ????((raw_sk=raw_prot.sock_array[hash])!=NULL)??
203. ?????????sock?*sknext=NULL;??
205. ????????raw_sk=get_sock_raw(raw_sk,?hash,??iph->saddr,?iph->daddr);??
207. ????????{??
209. ????????????{??
211. ????????????????sknext=get_sock_raw(raw_sk->next,?iph->saddr,?iph->daddr);??
213. ????????????????????skb1=skb_clone(skb,?GFP_ATOMIC);??
215. ????????????????????;????
217. ????????????????????raw_rcv(raw_sk,?skb1,iph->daddr);??
219. ????????????}??
221. ??????????????
223. ????????}??
225. ??????
227. h.raw?now?points?at?the?protocol?beyond?the?IP?header.?
229. ??
230. protocol?&?(MAX_INET_PROTOS?-1);??
231. ?????(ipprot?=?(?inet_protocol?*)inet_protos[hash];ipprot?!=?NULL;ipprot=(?inet_protocol?*)ipprot->next)??
233. ?????????sk_buff?*skb2;??
235. ?????????(ipprot->protocol?!=?iph->protocol)??
237. ????????
239. ?
241. ?
243. ?????????(ipprot->copy?||?raw_sk)??
245. ????????????skb2?=?skb_clone(skb,?GFP_ATOMIC);??
247. ????????????????;??
249. ??????????
251. ????????????skb2?=?skb;??
253. ????????flag?=?1;??
255. ????????????
257. ?
259. ??
260. handler(skb2,?opts_p???&opt?:?0,?iph->daddr,??
261. ????????????????(ntohs(iph->tot_len)?-?(iph->ihl?*?4)),??
262. saddr,?ipprot);??
263. ??
265. ??
267. ?
269. ?
271. ??
273. ????(raw_sk!=NULL)??????
274. daddr);??
275. ??????(!flag)???????
277. ?????????(brd?!=?IS_BROADCAST?&&?brd!=IS_MULTICAST)??
280. ??
282. }??

3、传输层

如果在IP数据报的首部标明的是使用TCP传输数据，则在上述函数中会调用tcp_rcv函数。该函数的大体处理流程为：

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