system76-edk2/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Option.c

/** @file
  IP4 option support functions.

Copyright (c) 2005 - 2018, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include "Ip4Impl.h"


/**
  Validate the IP4 option format for both the packets we received
  and will transmit.

  @param[in]  Option            The first byte of the option
  @param[in]  OptionLen         The length of the whole option
  @param[in]  Rcvd              The option is from the packet we received if TRUE,
                                otherwise the option we wants to transmit.

  @retval TRUE     The option is properly formatted
  @retval FALSE    The option is mal-formated

**/
BOOLEAN
Ip4OptionIsValid (
  IN UINT8                  *Option,
  IN UINT32                 OptionLen,
  IN BOOLEAN                Rcvd
  )
{
  UINT32                    Cur;
  UINT32                    Len;
  UINT32                    Point;

  Cur       = 0;

  while (Cur < OptionLen) {
    switch (Option[Cur]) {
    case IP4_OPTION_NOP:
      Cur++;
      break;

    case IP4_OPTION_EOP:
      Cur = OptionLen;
      break;

    case IP4_OPTION_LSRR:
    case IP4_OPTION_SSRR:
    case IP4_OPTION_RR:
      Len   = Option[Cur + 1];
      Point = Option[Cur + 2];

      //
      // SRR/RR options are formatted as |Type|Len|Point|Ip1|Ip2|...
      //
      if ((OptionLen - Cur < Len) || (Len < 3) || ((Len - 3) % 4 != 0)) {
        return FALSE;
      }

      if ((Point > Len + 1) || (Point % 4 != 0)) {
        return FALSE;
      }

      //
      // The Point must point pass the last entry if the packet is received
      // by us. It must point to 4 if the packet is to be sent by us for
      // source route option.
      //
      if ((Option[Cur] != IP4_OPTION_RR) &&
          ((Rcvd && (Point != Len + 1)) || (!Rcvd && (Point != 4)))) {

        return FALSE;
      }

      Cur += Len;
      break;

    default:
      Len = Option[Cur + 1];

      if ((OptionLen - Cur < Len) || (Len < 2)) {
        return FALSE;
      }

      Cur = Cur + Len;
      break;
    }

  }

  return TRUE;
}


/**
  Copy the option from the original option to buffer. It
  handles the details such as:
  1. whether copy the single IP4 option to the first/non-first
     fragments.
  2. Pad the options copied over to aligned to 4 bytes.

  @param[in]       Option            The original option to copy from
  @param[in]       OptionLen         The length of the original option
  @param[in]       FirstFragment     Whether it is the first fragment
  @param[in, out]  Buf               The buffer to copy options to. NULL
  @param[in, out]  BufLen            The length of the buffer

  @retval EFI_SUCCESS           The options are copied over
  @retval EFI_BUFFER_TOO_SMALL  Buf is NULL or BufLen provided is too small.

**/
EFI_STATUS
Ip4CopyOption (
  IN     UINT8              *Option,
  IN     UINT32             OptionLen,
  IN     BOOLEAN            FirstFragment,
  IN OUT UINT8              *Buf,           OPTIONAL
  IN OUT UINT32             *BufLen
  )
{
  UINT8                     OptBuf[40];
  UINT32                    Cur;
  UINT32                    Next;
  UINT8                     Type;
  UINT32                    Len;

  ASSERT ((BufLen != NULL) && (OptionLen <= 40));

  Cur   = 0;
  Next  = 0;

  while (Cur < OptionLen) {
    Type  = Option[Cur];
    Len   = Option[Cur + 1];

    if (Type == IP4_OPTION_NOP) {
      //
      // Keep the padding, in case that the sender wants to align
      // the option, say, to 4 bytes
      //
      OptBuf[Next] = IP4_OPTION_NOP;
      Next++;
      Cur++;

    } else if (Type == IP4_OPTION_EOP) {
      //
      // Don't append the EOP to avoid including only a EOP option
      //
      break;

    } else {
      //
      // don't copy options that is only valid for the first fragment
      //
      if (FirstFragment || (Type & IP4_OPTION_COPY_MASK) != 0) {
        CopyMem (OptBuf + Next, Option + Cur, Len);
        Next += Len;
      }

      Cur += Len;
    }
  }

  //
  // Don't append an EOP only option.
  //
  if (Next == 0) {
    *BufLen = 0;
    return EFI_SUCCESS;
  }

  //
  // Append an EOP if the end of option doesn't coincide with the
  // end of the IP header, that is, isn't aligned to 4 bytes..
  //
  if ((Next % 4) != 0) {
    OptBuf[Next] = IP4_OPTION_EOP;
    Next++;
  }

  //
  // Head length is in the unit of 4 bytes. Now, Len is the
  // acutal option length to appear in the IP header.
  //
  Len = ((Next + 3) &~0x03);

  //
  // If the buffer is too small, set the BufLen then return
  //
  if ((Buf == NULL) || (*BufLen < Len)) {
    *BufLen = Len;
    return EFI_BUFFER_TOO_SMALL;
  }

  //
  // Copy the option to the Buf, zero the buffer first to pad
  // the options with NOP to align to 4 bytes.
  //
  ZeroMem (Buf, Len);
  CopyMem (Buf, OptBuf, Next);
  *BufLen = Len;
  return EFI_SUCCESS;
}