51 lines
1.1 KiB
Go
51 lines
1.1 KiB
Go
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//go:build linux
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package dnstt
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import (
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"fmt"
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"syscall"
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)
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// OpenRawSocket creates an AF_PACKET raw socket for sniffing IPv4 packets.
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func OpenRawSocket() (int, error) {
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fd, err := syscall.Socket(syscall.AF_PACKET, syscall.SOCK_DGRAM, int(htons(syscall.ETH_P_IP)))
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if err != nil {
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return -1, fmt.Errorf("open raw socket: %w", err)
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}
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tv := syscall.Timeval{Sec: 0, Usec: 500000}
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_ = syscall.SetsockoptTimeval(fd, syscall.SOL_SOCKET, syscall.SO_RCVTIMEO, &tv)
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return fd, nil
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}
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// CaptureLoop records matching packets until stop is closed.
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func CaptureLoop(fd int, port int, collector *Collector, stop <-chan struct{}) {
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buf := make([]byte, 65535)
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for {
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select {
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case <-stop:
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return
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default:
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}
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n, _, err := syscall.Recvfrom(fd, buf, 0)
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if err != nil {
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if err == syscall.EAGAIN || err == syscall.EWOULDBLOCK || err == syscall.EINTR {
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continue
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}
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return
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}
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ProcessIPv4Packet(buf[:n], port, collector)
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}
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}
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// CloseRawSocket closes a socket opened by OpenRawSocket.
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func CloseRawSocket(fd int) error {
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return syscall.Close(fd)
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}
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func htons(v uint16) uint16 {
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return (v << 8) | (v >> 8)
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}
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