英文:
what syscall to use in order to obtain the value of some RTF_* flags
问题
使用go，我想从netstat(1)的手册页面中获取一些RTF_*标志的值（UGHS）：
G RTF_GATEWAY 目标需要通过中间人进行转发
H RTF_HOST 主机条目（否则为网络条目）
S RTF_STATIC 手动添加
U RTF_UP 可用路由
你知道我可以使用哪些系统调用/方法来获取这些值吗？我看到它们在https://golang.org/pkg/syscall/中被声明，但我想知道如何使用它们？
我需要找到添加到路由表中的网关的IP，主要是在连接到VPN时（在macOS、FreeBSD中使用netstat）：
netstat -rna -f inet | grep UGHS | awk '{print $1}'
有什么建议吗？
英文:
Using go, I would like to obtain the value of some RTF_* flags, (UGHS) from netstat(1) man page:
G RTF_GATEWAY Destination requires forwarding by intermediary
H RTF_HOST Host entry (net otherwise)
S RTF_STATIC Manually added
U RTF_UP Route usable
Any idea of what syscall/methods could I use to retrieve does values? I see they are declared https://golang.org/pkg/syscall/ but would like to know to use them?
I need this to find the IP of gateways added to the route table, mainly when connecting to VPN's, currently using netstat for this (withing macOS, FreeBSD):
netstat -rna -f inet | grep UGHS | awk '{print $1}'
Any ideas?
答案1
得分: 3
根据@JimB的建议，使用route包，我能够查询当前路由并获取与特定标志匹配的IP地址，例如UGSH和UGSc。
基本示例代码：
package main
import (
"fmt"
"net"
"syscall"
"golang.org/x/net/route"
)
const (
UGSH = syscall.RTF_UP | syscall.RTF_GATEWAY | syscall.RTF_STATIC | syscall.RTF_HOST
UGSc = syscall.RTF_UP | syscall.RTF_GATEWAY | syscall.RTF_STATIC | syscall.RTF_PRCLONING
)
func main() {
if rib, err := route.FetchRIB(syscall.AF_UNSPEC, route.RIBTypeRoute, 0); err == nil {
if msgs, err := route.ParseRIB(route.RIBTypeRoute, rib); err == nil {
for _, msg := range msgs {
m := msg.(*route.RouteMessage)
if m.Flags == UGSH || m.Flags == UGSc {
var ip net.IP
switch a := m.Addrs[syscall.AF_UNSPEC].(type) {
case *route.Inet4Addr:
ip = net.IPv4(a.IP[0], a.IP[1], a.IP[2], a.IP[3])
case *route.Inet6Addr:
ip = make(net.IP, net.IPv6len)
copy(ip, a.IP[:])
}
fmt.Printf("ip = %s\n", ip)
}
}
}
}
}
英文:
As @JimB suggested by using the route package I was able to query the current routes and get only IP's matching certain flags, in this case" UGSH, UGSc.
Basic example code:
package main
import (
"fmt"
"net"
"syscall"
"golang.org/x/net/route"
)
const (
UGSH = syscall.RTF_UP | syscall.RTF_GATEWAY | syscall.RTF_STATIC | syscall.RTF_HOST
UGSc = syscall.RTF_UP | syscall.RTF_GATEWAY | syscall.RTF_STATIC | syscall.RTF_PRCLONING
)
func main() {
if rib, err := route.FetchRIB(syscall.AF_UNSPEC, route.RIBTypeRoute, 0); err == nil {
if msgs, err := route.ParseRIB(route.RIBTypeRoute, rib); err == nil {
for _, msg := range msgs {
m := msg.(*route.RouteMessage)
if m.Flags == UGSH || m.Flags == UGSc {
var ip net.IP
switch a := m.Addrs[syscall.AF_UNSPEC].(type) {
case *route.Inet4Addr:
ip = net.IPv4(a.IP[0], a.IP[1], a.IP[2], a.IP[3])
case *route.Inet6Addr:
ip = make(net.IP, net.IPv6len)
copy(ip, a.IP[:])
}
fmt.Printf("ip = %s\n", ip)
}
}
}
}
}
答案2
得分: 0
strace netstat的等效命令（在MacOS上是dtruss，请参考https://opensourcehacker.com/2011/12/02/osx-strace-equivalent-dtruss-seeing-inside-applications-what-they-do-and-why-they-hang/）将给出netstat所进行的系统调用列表，您可以根据需要确定您需要进行的系统调用。
英文:
The equivalent of strace netstat (dtruss on MacOS, see https://opensourcehacker.com/2011/12/02/osx-strace-equivalent-dtruss-seeing-inside-applications-what-they-do-and-why-they-hang/) should give you a list of system calls it makes and you can decide what system calls you need to make for your problem.
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