github.com/hugelgupf/u-root@v0.0.0-20191023214958-4807c632154c/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/dhclient"
    31  	"github.com/u-root/u-root/pkg/netboot"
    32  	"github.com/u-root/u-root/pkg/urlfetch"
    33  )
    34  
    35  var (
    36  	ifName  = "^e.*"
    37  	noLoad  = flag.Bool("no-load", false, "get DHCP response, but don't load the kernel")
    38  	dryRun  = flag.Bool("dry-run", false, "download kernel, but don't kexec it")
    39  	verbose = flag.Bool("v", false, "Verbose output")
    40  )
    41  
    42  const (
    43  	dhcpTimeout = 5 * time.Second
    44  	dhcpTries   = 3
    45  )
    46  
    47  // Netboot boots all interfaces matched by the regex in ifaceNames.
    48  func Netboot(ifaceNames string) error {
    49  	filteredIfs, err := dhclient.Interfaces(ifaceNames)
    50  	if err != nil {
    51  		return err
    52  	}
    53  
    54  	ctx, cancel := context.WithTimeout(context.Background(), (1<<dhcpTries)*dhcpTimeout)
    55  	defer cancel()
    56  
    57  	c := dhclient.Config{
    58  		Timeout: dhcpTimeout,
    59  		Retries: dhcpTries,
    60  	}
    61  	if *verbose {
    62  		c.LogLevel = dhclient.LogSummary
    63  	}
    64  	r := dhclient.SendRequests(ctx, filteredIfs, true, true, c)
    65  
    66  	for {
    67  		select {
    68  		case <-ctx.Done():
    69  			return ctx.Err()
    70  
    71  		case result, ok := <-r:
    72  			if !ok {
    73  				log.Printf("Configured all interfaces.")
    74  				return fmt.Errorf("nothing bootable found")
    75  			}
    76  			if result.Err != nil {
    77  				continue
    78  			}
    79  
    80  			if err := result.Lease.Configure(); err != nil {
    81  				log.Printf("Failed to configure lease %s: %v", result.Lease, err)
    82  				// Boot further regardless of lease configuration result.
    83  				//
    84  				// If lease failed, fall back to use locally configured
    85  				// ip/ipv6 address.
    86  			}
    87  			img, err := netboot.BootImage(urlfetch.DefaultSchemes, result.Lease)
    88  			if err != nil {
    89  				log.Printf("Failed to boot lease %v: %v", result.Lease, err)
    90  				continue
    91  			}
    92  
    93  			// Cancel other DHCP requests in flight.
    94  			cancel()
    95  			log.Printf("Got configuration: %s", img)
    96  
    97  			if *noLoad {
    98  				return nil
    99  			}
   100  			if err := img.Load(*dryRun); err != nil {
   101  				return fmt.Errorf("kexec load of %v failed: %v", img, err)
   102  			}
   103  			if *dryRun {
   104  				return nil
   105  			}
   106  			if err := boot.Execute(); err != nil {
   107  				return fmt.Errorf("kexec of %v failed: %v", img, err)
   108  			}
   109  
   110  			// Kexec should either return an error or not return.
   111  			panic("unreachable")
   112  		}
   113  	}
   114  }
   115  
   116  func main() {
   117  	flag.Parse()
   118  	if len(flag.Args()) > 1 {
   119  		log.Fatalf("Only one regexp-style argument is allowed, e.g.: " + ifName)
   120  	}
   121  
   122  	if len(flag.Args()) > 0 {
   123  		ifName = flag.Args()[0]
   124  	}
   125  
   126  	if err := Netboot(ifName); err != nil {
   127  		log.Fatal(err)
   128  	}
   129  }