Attachment 254879 Details for Bug 282495 – Simple Go executable that shows an adapted internal Go sendfile wrapper exercising the apparent bug

Simple Go executable that shows an adapted internal Go sendfile wrapper exercising the apparent bug

main.go (text/plain), 2.54 KB, created by pieter on 2024-11-02 16:27:07 UTC

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Creator: pieter

Created: 2024-11-02 16:27:07 UTC

Size: 2.54 KB

patch

obsolete

>package main
>
>import (
>	"net"
>	"os"
>	"syscall"
>	"fmt"
>	//"io"
>)
>
>func CheckError(err error) {
>	if err != nil {
>		fmt.Fprintf(os.Stderr, "Fatal error: %s\n", err.Error())
>		os.Exit(1)
>	}
>}
>
>const maxSendfileSize int = 4 << 20
>func SendFile(dst int, src int, remain int64) (written int64, err error, handled bool) {
>	for remain > 0 {
>		fmt.Printf("Entering loop, remain = %d\n", remain)
>		n := maxSendfileSize
>		if int64(n) > remain {
>			n = int(remain)
>		}
>		n, err = syscall.Sendfile(dst, src, nil, n)
>		fmt.Printf("syscall returned n=%d, err=%s\n", n, err)
>
>		if n > 0 {
>			written += int64(n)
>			remain -= int64(n)
>			fmt.Printf("Sendfile syscall success, written: %d, remain: %d\n", written, remain)
>			continue
>		} else if err != syscall.EAGAIN && err != syscall.EINTR {
>			// This includes syscall.ENOSYS (no kernel
>			// support) and syscall.EINVAL (fd types which
>			// don't implement sendfile), and other errors.
>			// We should end the loop when there is no error
>			// returned from sendfile(2) or it is not a retryable error.
>			fmt.Printf("Error, but not EAGAIN nor EINTR, breaking out of the loop\n")
>			break
>		}
>		if err == syscall.EINTR {
>			fmt.Printf("Error EINTR, looping back\n")
>			continue
>		}
>		if err == syscall.EAGAIN {
>			fmt.Printf("Error EAGAIN, stopping to see if anything was sent\n")
>			break
>		}
>/*
>		// In my rewrite there's no dstFD and couldn't directly find what this does. But it doesn't seem
>		// to matter for reproducing the issue.
>		if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
>			break
>		}
>*/
>	}
>	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
>	return
>}
>
>func main() {
>	srcFile := "./file2"
>	serverAddr := "localhost:4040"
>
>	// server start listenning
>	server, err := net.Listen("tcp", serverAddr)
>	CheckError(err)
>	defer server.Close()
>
>	for true {
>		sendFile(server, srcFile)
>	}
>}
>
>
>func sendFile(server net.Listener, srcFile string) {
>	// accept connection
>	conn, err := server.Accept()
>	CheckError(err)
>
>	// open file to send
>	fi, err := os.Open(srcFile)
>	CheckError(err)
>	defer fi.Close()
>
>	fs, err := fi.Stat()
>	CheckError(err)
>	n := fs.Size()
>
>	src := int(fi.Fd())
>	dstF, _ := conn.(*net.TCPConn).File()
>	CheckError(err)
>	dst := int(dstF.Fd())
>
>	
>	// set non-blocking
>	syscall.SetNonblock(dst, true);
>
>	// send file to client
>	//n, err = syscall.Sendfile(dst, src, nil, n)
>	//_, err = io.CopyN(conn, fi, n)
>	//n, err = conn.(*net.TCPConn).ReadFrom(fi)
>
>	n, err, handled := SendFile(dst, src, n)
>	CheckError(err)
>	fmt.Fprintf(os.Stdout, "Wrote %d bytes, handled: %s", n, handled)
>	conn.(*net.TCPConn).Close()
>}
>

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Attachments on bug 282495: 254879