機器自己連自己開的 server，使用者無論是設定機器本身 IP 還是 127.0.0.1 都不行。以下是 client 連線部份的程式：
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90 | #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <time.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/select.h>
int main(int argc , char *argv[])
{
int sockfd = 0;
sockfd = socket(PF_INET , SOCK_STREAM | SOCK_CLOEXEC, IPPROTO_TCP);
if (sockfd == -1)
{
printf("Fail to create a socket.\n");
}
printf("socket ok\n");
struct sockaddr_in info = {0};
info.sin_family = AF_INET;
info.sin_addr.s_addr = inet_addr("127.0.0.1");
info.sin_port = htons(502);
char *buffer = "eth1";
if(setsockopt(sockfd, SOL_SOCKET, SO_BINDTODEVICE, buffer, strlen(buffer)))
{
}
int nFcntlFlag = 0;
nFcntlFlag = fcntl(sockfd, F_GETFL, 0);
nFcntlFlag |= O_NONBLOCK;
fcntl(sockfd, F_SETFL, nFcntlFlag);
printf("connect...\n");
int err = connect(sockfd,(struct sockaddr *)&info, sizeof(info));
if (err==-1 && errno == EINPROGRESS)
{
fd_set wset;
struct timeval timeout = {0};
FD_ZERO(&wset);
FD_SET(sockfd, &wset);
timeout.tv_sec = 1;
timeout.tv_usec = 0;
int ret = select(sockfd + 1, NULL, &wset, NULL, &timeout);
if (ret > 0)
{
if (FD_ISSET(sockfd, &wset))
{
int err;
socklen_t len = sizeof(int);
if (0 == getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &err, &len))
{
if (err == 0) // connected
{
printf("tcp_open, connected, socket %d\n", sockfd);
}
else
{
printf("err is not zero, err %d\n", err);
}
}
}
else
{
printf("fd is not set\n");
}
}
else
{
printf("select fail\n");
}
}
else if (err == -1)
printf("connect fail\n");
else if (err == 0)
printf("connect ok\n");
printf("close Socket\n");
close(sockfd);
return 0;
} |
主要是 client 會 bind 使用者指定的網路界面，這邊是 eth1。然而，無論是使用機器 IP 還是 127.0.0.1 都不能連線成功。透過 perf 觀察到的網路界面似乎都是 lo 在作用：
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13 | # perf_4.19 trace --no-syscalls --event 'net:*' ./socket
start
socket ok
connect...
sh: 1: /perf-read-vdso32: not found
0.000 net:net_dev_queue:dev=lo skbaddr=0xffff9907f9bbcee8 len=74
0.140 net:net_dev_start_xmit:dev=lo queue_mapping=0 skbaddr=0xffff9907f9bbcee8 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 len=74 data_len=0 network_offset=14 transport_offset_valid=1 transport_offset=34 tx_flags=0 gso_size=0 gso_segs=1 gso_type=0x1
0.164 net:netif_rx_entry:dev=lo napi_id=0x2 queue_mapping=0 skbaddr=0xffff9907f9bbcee8 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 hash=0xfca661f3 l4_hash=1 len=60 data_len=0 truesize=1280 mac_header_valid=1 mac_header=-14 nr_frags=0 gso_size=0 gso_type=0x1
0.186 net:netif_rx:dev=lo skbaddr=0xffff9907f9bbcee8 len=60
0.208 net:net_dev_xmit:dev=lo skbaddr=0xffff9907f9bbcee8 len=74 rc=0
root@RootfsDebian:~# select ret 0
select fail
close Socket
|
如果 client 程式改成不 bind 就連線成功。perf 的結果如下：
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23 | # perf_4.19 trace --no-syscalls --event 'net:*' ./socket
start
socket ok
connect...
select ret 1
tcp_open, connected, socket 3
close Socket
sh: 1: /perf-read-vdso32: not found
0.000 net:net_dev_queue:dev=lo skbaddr=0xffff9907f83a1ee8 len=74
1.436 net:net_dev_start_xmit:dev=lo queue_mapping=0 skbaddr=0xffff9907f83a1ee8 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 len=74 data_len=0 network_offset=14 transport_offset_valid=1 transport_offset=34 tx_flags=0 gso_size=0 gso_segs=1 gso_type=0x1
1.486 net:netif_rx_entry:dev=lo napi_id=0x2 queue_mapping=0 skbaddr=0xffff9907f83a1ee8 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 hash=0xd4094cf6 l4_hash=1 len=60 data_len=0 truesize=1280 mac_header_valid=1 mac_header=-14 nr_frags=0 gso_size=0 gso_type=0x1
1.508 net:netif_rx:dev=lo skbaddr=0xffff9907f83a1ee8 len=60
1.529 net:net_dev_xmit:dev=lo skbaddr=0xffff9907f83a1ee8 len=74 rc=0
1.630 net:net_dev_queue:dev=lo skbaddr=0xffff9907f5eb8600 len=66
1.653 net:net_dev_start_xmit:dev=lo queue_mapping=0 skbaddr=0xffff9907f5eb8600 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 len=66 data_len=0 network_offset=14 transport_offset_valid=1 transport_offset=34 tx_flags=0 gso_size=0 gso_segs=1 gso_type=0x1
1.673 net:netif_rx_entry:dev=lo napi_id=0x2 queue_mapping=0 skbaddr=0xffff9907f5eb8600 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 hash=0xd4094cf6 l4_hash=1 len=52 data_len=0 truesize=2 mac_header_valid=1 mac_header=-14 nr_frags=0 gso_size=0 gso_type=0x1
1.692 net:netif_rx:dev=lo skbaddr=0xffff9907f5eb8600 len=52
1.712 net:net_dev_xmit:dev=lo skbaddr=0xffff9907f5eb8600 len=66 rc=0
1.950 net:net_dev_queue:dev=lo skbaddr=0xffff9907f83a1ee8 len=66
1.977 net:net_dev_start_xmit:dev=lo queue_mapping=0 skbaddr=0xffff9907f83a1ee8 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 len=66 data_len=0 network_offset=14 transport_offset_valid=1 transport_offset=34 tx_flags=0 gso_size=0 gso_segs=1 gso_type=0x1
1.998 net:netif_rx_entry:dev=lo napi_id=0x2 queue_mapping=0 skbaddr=0xffff9907f83a1ee8 vlan_tagged=0 vlan_proto=0x0000 vlan_tci=0x0000 protocol=0x0800 ip_summed=3 hash=0xd4094cf6 l4_hash=1 len=52 data_len=0 truesize=1280 mac_header_valid=1 mac_header=-14 nr_frags=0 gso_size=0 gso_type=0x1
2.016 net:netif_rx:dev=lo skbaddr=0xffff9907f83a1ee8 len=52
2.039 net:net_dev_xmit:dev=lo skbaddr=0xffff9907f83a1ee8 len=66 rc=0
|
實際原理其實有點模糊，感覺系統知道是自己機器後，固定由 lo 處理。但我們又 bind 要由 eth1 處理，就卡住了。
或許處理方式是判斷到是 127.0.0.1 或者自己機器 IP 時，不要做 bind。
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