github.hscsec.cn/u-root/u-root@v7.0.0+incompatible/cmds/boot/pxeboot/pxeboot.go (about)

     1  // Copyright 2017-2018 the u-root Authors. All rights reserved
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Command pxeboot implements PXE-based booting.
     6  //
     7  // pxeboot combines a DHCP client with a TFTP/HTTP client to download files as
     8  // well as pxelinux and iPXE configuration file parsing.
     9  //
    10  // PXE-based booting requests a DHCP lease, and looks at the BootFileName and
    11  // ServerName options (which may be embedded in the original BOOTP message, or
    12  // as option codes) to find something to boot.
    13  //
    14  // This BootFileName may point to
    15  //
    16  // - an iPXE script beginning with #!ipxe
    17  //
    18  // - a pxelinux.0, in which case we will ignore the pxelinux and try to parse
    19  //   pxelinux.cfg/<files>
    20  package main
    21  
    22  import (
    23  	"context"
    24  	"flag"
    25  	"fmt"
    26  	"log"
    27  	"time"
    28  
    29  	"github.com/u-root/u-root/pkg/boot"
    30  	"github.com/u-root/u-root/pkg/boot/bootcmd"
    31  	"github.com/u-root/u-root/pkg/boot/menu"
    32  	"github.com/u-root/u-root/pkg/boot/netboot"
    33  	"github.com/u-root/u-root/pkg/curl"
    34  	"github.com/u-root/u-root/pkg/dhclient"
    35  	"github.com/u-root/u-root/pkg/ulog"
    36  )
    37  
    38  var (
    39  	ifName      = "^e.*"
    40  	noLoad      = flag.Bool("no-load", false, "get DHCP response, print chosen boot configuration, but do not download + exec it")
    41  	noExec      = flag.Bool("no-exec", false, "download boot configuration, but do not exec it")
    42  	noNetConfig = flag.Bool("no-net-config", false, "get DHCP response, but do not apply the network config it to the kernel interface")
    43  	verbose     = flag.Bool("v", false, "Verbose output")
    44  )
    45  
    46  const (
    47  	dhcpTimeout = 5 * time.Second
    48  	dhcpTries   = 3
    49  )
    50  
    51  // NetbootImages requests DHCP on every ifaceNames interface, and parses
    52  // netboot images from the DHCP leases. Returns bootable OSes.
    53  func NetbootImages(ifaceNames string) ([]boot.OSImage, error) {
    54  	filteredIfs, err := dhclient.Interfaces(ifaceNames)
    55  	if err != nil {
    56  		return nil, err
    57  	}
    58  
    59  	ctx, cancel := context.WithTimeout(context.Background(), (1<<dhcpTries)*dhcpTimeout)
    60  	defer cancel()
    61  
    62  	c := dhclient.Config{
    63  		Timeout: dhcpTimeout,
    64  		Retries: dhcpTries,
    65  	}
    66  	if *verbose {
    67  		c.LogLevel = dhclient.LogSummary
    68  	}
    69  	r := dhclient.SendRequests(ctx, filteredIfs, true, true, c, 30*time.Second)
    70  
    71  	for {
    72  		select {
    73  		case <-ctx.Done():
    74  			return nil, ctx.Err()
    75  
    76  		case result, ok := <-r:
    77  			if !ok {
    78  				return nil, fmt.Errorf("nothing bootable found, all interfaces are configured or timed out")
    79  			}
    80  			iname := result.Interface.Attrs().Name
    81  			if result.Err != nil {
    82  				log.Printf("Could not configure %s for %s: %v", iname, result.Protocol, result.Err)
    83  				continue
    84  			}
    85  
    86  			if *noNetConfig {
    87  				log.Printf("Skipping configuring %s with lease %s", iname, result.Lease)
    88  			} else if err := result.Lease.Configure(); err != nil {
    89  				log.Printf("Failed to configure lease %s: %v", result.Lease, err)
    90  				// Boot further regardless of lease configuration result.
    91  				//
    92  				// If lease failed, fall back to use locally configured
    93  				// ip/ipv6 address.
    94  			}
    95  
    96  			// Don't use the other context, as it's for the DHCP timeout.
    97  			imgs, err := netboot.BootImages(context.Background(), ulog.Log, curl.DefaultSchemes, result.Lease)
    98  			if err != nil {
    99  				log.Printf("Failed to boot lease %v: %v", result.Lease, err)
   100  				continue
   101  			}
   102  			return imgs, nil
   103  		}
   104  	}
   105  }
   106  
   107  func main() {
   108  	flag.Parse()
   109  	if len(flag.Args()) > 1 {
   110  		log.Fatalf("Only one regexp-style argument is allowed, e.g.: " + ifName)
   111  	}
   112  	if len(flag.Args()) > 0 {
   113  		ifName = flag.Args()[0]
   114  	}
   115  
   116  	images, err := NetbootImages(ifName)
   117  	if err != nil {
   118  		log.Printf("Netboot failed: %v", err)
   119  	}
   120  
   121  	menuEntries := menu.OSImages(*verbose, images...)
   122  	menuEntries = append(menuEntries, menu.Reboot{})
   123  	menuEntries = append(menuEntries, menu.StartShell{})
   124  
   125  	// Boot does not return.
   126  	bootcmd.ShowMenuAndBoot(menuEntries, nil, *noLoad, *noExec)
   127  }