一、ifconfig显示
[root@10g-host4 new]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:26:B9:4A:FC:EA
inet addr:192.168.100.4 Bcast:192.168.100.255 Mask:255.255.255.0
inet6 addr: fe80::226:b9ff:fe4a:fcea/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:272 errors:0 dropped:0 overruns:0 frame:0
TX packets:66 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:19904 (19.4 KiB) TX bytes:10312 (10.0 KiB)
eth2 Link encap:Ethernet HWaddr 00:16:31:F0:9E:94
inet addr:192.168.99.4 Bcast:192.168.99.255 Mask:255.255.255.0
inet6 addr: fe80::216:31ff:fef0:9e94/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:941824733 errors:0 dropped:584879511 overruns:0 frame:0
TX packets:941801077 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:56509485448 (52.6 GiB) TX bytes:50857262610 (47.3 GiB)
eth2:0 Link encap:Ethernet HWaddr 00:16:31:F0:9E:94
inet addr:192.168.99.20 Bcast:192.168.99.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:49 errors:0 dropped:0 overruns:0 frame:0
TX packets:49 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3596 (3.5 KiB) TX bytes:3596 (3.5 KiB)
二、/proc/net/dev
[root@10g-host4 new]# cat /proc/net/dev
Inter-| Receive | Transmit
face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed
lo: 3596 49 0 0 0 0 0 0 3596 49 0 0 0 0 0 0
eth0: 39710 560 0 0 0 0 0 118 14850 93 0 0 0 0 0 0
eth1: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
sit0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
eth2:123635538320 2060592241 0 1236548294 0 0 0 0 111270716166 2060568737 0 0 0 0 0 0
eth3: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
二、ifconfig源代码主要路径
ifconfig源码位于net-tool-1.6源码包，主要执行路径如下：
main( )
-> if_print( ) //参数为eth2
->lookup_interface( )
->do_if_fetch( )
->ife_print( )
->ife_print_long( )
这样打印ifconfig看到的收发统计信息：
printf(_("RX packets:%llu errors:%lu dropped:%lu overruns:%lu frame:%lu\n"),
ptr->stats.rx_packets, ptr->stats.rx_errors,
ptr->stats.rx_dropped, ptr->stats.rx_fifo_errors,
ptr->stats.rx_frame_errors);
printf(_("TX packets:%llu errors:%lu dropped:%lu overruns:%lu carrier:%lu\n"),
ptr->stats.tx_packets, ptr->stats.tx_errors,
ptr->stats.tx_dropped, ptr->stats.tx_fifo_errors,
ptr->stats.tx_carrier_errors);
而stats结构体定义如下：
128struct net_device_stats
129{
130 unsigned long rx_packets; /* total packets received */
131 unsigned long tx_packets; /* total packets transmitted */
132 unsigned long rx_bytes; /* total bytes received */
133 unsigned long tx_bytes; /* total bytes transmitted */
134 unsigned long rx_errors; /* bad packets received */
135 unsigned long tx_errors; /* packet transmit problems */
136 unsigned long rx_dropped; /* no space in linux buffers */
137 unsigned long tx_dropped; /* no space available in linux */
138 unsigned long multicast; /* multicast packets received */
139 unsigned long collisions;
140
141 /* detailed rx_errors: */
142 unsigned long rx_length_errors;
143 unsigned long rx_over_errors; /* receiver ring buff overflow */
144 unsigned long rx_crc_errors; /* recved pkt with crc error */
145 unsigned long rx_frame_errors; /* recv'd frame alignment error */
146 unsigned long rx_fifo_errors; /* recv'r fifo overrun */
147 unsigned long rx_missed_errors; /* receiver missed packet */
148
149 /* detailed tx_errors */
150 unsigned long tx_aborted_errors;
151 unsigned long tx_carrier_errors;
152 unsigned long tx_fifo_errors;
153 unsigned long tx_heartbeat_errors;
154 unsigned long tx_window_errors;
155
156 /* for cslip etc */
157 unsigned long rx_compressed;
158 unsigned long tx_compressed;
159};
而这些打印信息是从哪里来的呢？
在ixgbe万兆网卡驱动中，ixgbe_update_stats( )函数中
net_stats->rx_bytes = bytes;
net_stats->rx_packets = packets;
net_stats->tx_bytes = bytes;
net_stats->tx_packets = packets;
/* Rx Errors */
net_stats->rx_errors = hwstats->crcerrs + hwstats->rlec;
net_stats->rx_dropped = 0;
net_stats->rx_length_errors = hwstats->rlec;
net_stats->rx_crc_errors = hwstats->crcerrs;
net_stats->rx_missed_errors = total_mpc;
抠一下细节：
ifconfig明显中的dropped字段值应该来自于net_device_stats->rx_dropped，
可是ixgbe驱动里面设置为0了，为甚还会显示呢？
来源：https://www.cnblogs.com/mylinuxer/p/4200727.html