原创 为AM335x移植Linux内核主线代码(37)调试Ethernet之二

第三次执行inet_ioctl函数：
[   27.297526] ================================> inet_ioctl SSSS                
[   27.303692] ====> ioctl_num = 3 cmd = 0x8914                                 
[   27.308188] ====> delay 5s.                                                  
[   32.284443] ====> GIFADDR/SIFADDR ......                                     
[   32.288554] ====> devinet_ioctl SSSS                                         
[   32.292298] ====> ifr.ifr_name = lo                                          
[   32.295979] ====> switch (cmd) 1                                             
[   32.299369] ====> switch (cmd) 2                                             
[   32.302861] ====> dev_change_flags SSSS                                      
[   32.306915] ====> dev->flags = 0x8, flags = 0x49                             
[   32.311751] ----> __dev_change_flags SSSS                                    
[   32.315976] ----> dev_flags = 0x8                                            
[   32.319447] ----> dev_flags = 0x8                                            
[   32.322915] ----> dev_set_rx_mode IIII                                       
[   32.327220] ====> __dev_set_rx_mode SSSS                                     
[   32.331339] ====> no IFF_UP                                                  
[   32.334328] ----> IFF_UP = 0x1 old_flags = 0x8                               
[   32.338983] 1111 __dev_open start                                            
[   32.342451] 1111 netif_device_present IIII                                   
[   32.346770] 1111 netpoll_poll_disable IIII                                   
[   32.351060] 1111 call_netdevice_notifiers IIII                               
[   32.355747] 1111 notifier_to_errno IIII                                      
[   32.359763] 1111 set_bit __LINK_STATE_START                                  
[   32.364258] 1111 netpoll_poll_enable IIII                                    
[   32.368455] 2222 __dev_open middle                                           
[   32.372015] 2222 dev_set_rx_mode IIII                                        
[   32.375873] ====> __dev_set_rx_mode SSSS                                     
[   32.379980] ====> no IFF_UNICAST_FLT                                         
[   32.383774] 3333 __dev_open over                                             
[   32.387156] ----> __dev_change_flags EEEE                                    
[   32.391354] ----> __dev_notify_flags SSSS                                    
[   32.396088] ----> __dev_notify_flags EEEE                                    
[   32.400299] ====> changes = 0x1                                              
[   32.403645] ====> dev_change_flags EEEE                                      
[   32.407667] ====> devinet_ioctl EEEE ret = 0                                 
[   32.412137] =========================> inet_ioctl EEEEEEEEEEEEEE

0x8914被定义为宏SIOCSIFFLAGS，这个函数稍微复杂一些，因为devinet_ioctl函数会调用net/core/dev.c中的dev_change_flags函数。由于flags中关键的IFF_UP参数，使得由原来的0x08变成了0x09。

第四次执行inet_ioctl函数（同第二步）：
[   16.399259] ================================> inet_ioctl SSSS
[   16.405364] ====> cmd = 0x8913
[   16.408562] ====> NO VALID SIOC*
[   16.411940] =========================> inet_ioctl EEEEEEEEEEEEEE

第五次执行inet_ioctl函数：
[   37.417057] ================================> inet_ioctl SSSS                
[   37.423199] ====> ioctl_num = 5 cmd = 0x8914                                 
[   37.427671] ====> delay 5s.                                                  
[   42.403872] ====> GIFADDR/SIFADDR ......                                     
[   42.407983] ====> devinet_ioctl SSSS                                         
[   42.411727] ====> ifr.ifr_name = lo                                          
[   42.415406] ====> switch (cmd) 1                                             
[   42.418794] ====> switch (cmd) 2                                             
[   42.422263] ====> dev_change_flags SSSS                                      
[   42.426305] ====> dev->flags = 0x9, flags = 0x49                             
[   42.431138] ----> __dev_change_flags SSSS                                    
[   42.435358] ----> dev_flags = 0x9                                            
[   42.438827] ----> dev_flags = 0x9                                            
[   42.442296] ----> dev_set_rx_mode IIII                                       
[   42.446246] ====> __dev_set_rx_mode SSSS                                     
[   42.450351] ====> no IFF_UNICAST_FLT                                         
[   42.454119] ----> __dev_change_flags EEEE                                    
[   42.458317] ----> __dev_notify_flags SSSS                                    
[   42.462513] ----> __dev_notify_flags EEEE                                    
[   42.466731] ====> changes = 0x0                                              
[   42.470019] ====> dev_change_flags EEEE                                      
[   42.474061] ====> devinet_ioctl EEEE ret = 0                                 
[   42.478532] =========================> inet_ioctl EEEEEEEEEEEEEE

0x8914被定义为宏SIOCSIFFLAGS，这是第二次执行了，flags的值仍然为0x09；
Anyway，继续往下看～

第六次执行inet_ioctl函数（同第二步）：
[   16.589222] ================================> inet_ioctl SSSS
[   16.595428] ====> cmd = 0x8913
[   16.598629] ====> NO VALID SIOC*
[   16.602006] =========================> inet_ioctl EEEEEEEEEEEEEE

第一次到第六次对ioctl的执行，都是对本地网卡的操作，也就是对127.0.0.1的操作。这也是为什么dev_set_rx_mode函数调用的ops->ndo_*函数们没有被赋值的原因，因为本地网卡哪里来的对cpsw外设和PHY寄存器的操作呢？它不过是个虚拟出来的网卡罢了。
ping本地网卡不会丢包，永远都是LOOPBACK，简直是网络调试利器～～～

下面是more and more的inet_ioctl函数分析，而且是对eth0的了；
很多是吧～很麻烦是吧～Well, life is not simple. 哇哈哈哈哈！