title: Valgrind giving error but everything seems fine
body: <p>This one seems like a duplicate of my previous post but  it is not.....</p>
  
  <p>Here Valgrind giving the following error:</p>
  
  <pre><code> udit@udit-Dabba ~/mec $  valgrind --leak-check=full
   sendip -v -p ipv6 -f file.txt -6s ::1 -p esp -es 0x20 -eq 0x40
   -ei z30 -eI z100  -p tcp -ts 21 -td 21 ::2  
  
   ==4331== Memcheck, a memory error detector
   ==4331== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
   ==4331== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info
   ==4331== Command: sendip -v -p ipv6 -f file.txt -6s ::1 -p esp -es 0x20
   -eq 0x40 -ei z30 -eI z100 -p tcp -ts 21 -td 21 ::2
  ==4331== 
  esp
  Added 43 options
  Initializing module ipv6
  Initializing module esp
  Initializing module tcp
  ==4331== Invalid write of size 4
  ==4331==    at 0x4027EB8: memcpy (mc_replace_strmem.c:635)
  ==4331==    by 0x4032269: do_opt (esp.c:113)
  ==4331==    by 0x804A51D: main (sendip.c:575)
  ==4331==  Address 0x41ceab0 is 144 bytes inside a block of size 146 alloc'd
  ==4331==    at 0x402699A: realloc (vg_replace_malloc.c:525)
  ==4331==    by 0x4032231: do_opt (esp.c:111)
  ==4331==    by 0x804A51D: main (sendip.c:575)
  ==4331== 
  
  valgrind: m_mallocfree.c:225 (mk_plain_bszB): Assertion 'bszB != 0' failed.
  valgrind: This is probably caused by your program erroneously writing past the
  end of a heap block and corrupting heap metadata.  If you fix any
  invalid writes reported by Memcheck, this assertion failure will
  probably go away.  Please try that before reporting this as a bug.
  
  ==4331==    at 0x380282BD: report_and_quit (m_libcassert.c:193)
  ==4331==    by 0x38028415: vgPlain_assert_fail (m_libcassert.c:267)
  ==4331==    by 0x380351E7: vgPlain_arena_malloc (m_mallocfree.c:225)
  ==4331==    by 0x380662C7: vgPlain_cli_malloc (replacemalloc_core.c:83)
  ==4331==    by 0x38001FA8: vgMemCheck_new_block (mc_malloc_wrappers.c:201)
  ==4331==    by 0x38002196: vgMemCheck_malloc (mc_malloc_wrappers.c:238)
  ==4331==    by 0x38068BF8: vgPlain_scheduler (scheduler.c:1394)
  ==4331==    by 0x3807A354: run_a_thread_NORETURN (syswrap-linux.c:94)
  
  sched status:
  running_tid=1
  
  Thread 1: status = VgTs_Runnable
  ==4331==    at 0x40268A4: malloc (vg_replace_malloc.c:236)
  ==4331==    by 0x4152415: gethostbyname2 (getXXbyYY.c:103)
  ==4331==    by 0x402CC68: set_addr (ipv6.c:33)
  ==4331==    by 0x804A642: main (sendip.c:594)
  
  
  Note: see also the FAQ in the source distribution.
  It contains workarounds to several common problems.
  In particular, if Valgrind aborted or crashed after
  identifying problems in your program, there's a good chance
  that fixing those problems will prevent Valgrind aborting or
  crashing, especially if it happened in m_mallocfree.c.
  
  If that doesn't help, please report this bug to: www.valgrind.org
  
  In the bug report, send all the above text, the valgrind
  version, and what OS and version you are using.  Thanks.
  </code></pre>
  
  <p><strong>esp.c</strong> (line no. 113)</p>
  
  <pre><code>  case 'eI':       /* ICV data (variable length) */
                     /* For right now, we will do either random generation
                     * or a user-provided string. We put it in the header,
                     * then move it into the trailer in finalize.
                     */
              length = stringargument(arg, &amp;temp);
              priv-&gt;icvlen = length;
              pack-&gt;alloc_len += length;
              pack-&gt;data = realloc(esp, pack-&gt;alloc_len);
              esp = (esp_header *)pack-&gt;data;                                                                              
        113:      
              memcpy(&amp;esp-&gt;tail.ivicv[priv-&gt;ivlen],temp, priv-&gt;icvlen);
              pack-&gt;modified |= ESP_MOD_ICV;
  </code></pre>
  
  <p>These are the respective header files which I suppose may help in debugging ......</p>
  
  <p><strong>ip6.h</strong></p>
  
  <pre><code>/*
   * authentication header
  */
  struct ip_auth_hdr {
      u_int8_t  nexthdr;
      u_int8_t  hdrlen;       /* This one is measured in 32 bit units! */
      u_int16_t reserved;
      u_int32_t spi;
      u_int32_t seq_no;       /* Sequence number */
      u_int8_t  auth_data[0]; /* Variable len but &gt;=4. Mind the
                                 64 bit alignment! */
   #define icv     auth_data       /* rfc 4302 name */
      /* TBD - high-order sequence number */
  
   };
  
  /*
   * encapsulated security payload header
   */
   struct ip_esp_hdr {
      u_int32_t spi;
      u_int32_t seq_no;       /* Sequence number */
      u_int8_t  enc_data[0];  /* Variable len but &gt;=8. Mind the
                               64 bit alignment! */
    };
  </code></pre>
  
  <p><strong>esp.h</strong></p>
  
  <pre><code> struct ip_esp_tail {
      u_int8_t padlen;        /* padding is pushed before tail */
      u_int8_t nexthdr;
      u_int32_t ivicv[0];     /* both IV and ICV, if any */
   };
  
   struct ip_esp_headtail {
      struct ip_esp_hdr hdr;
      struct ip_esp_tail tail;
    };
  
    typedef struct ip_esp_headtail esp_header;
  
    #define ESP_MIN_PADDING 4 
  
    typedef struct ip_esp_private { /* keep track of things privately */
      u_int32_t type;         /* type = IPPROTO_ESP */
      u_int32_t ivlen;        /* length of IV portion */
      u_int32_t icvlen;       /* length of ICV portion */
      u_int32_t keylen;       /* length of "key" (not transmitted data) */
      u_int32_t key[0];       /* key itself */
    } esp_private;
  
    struct ip_auth_hdr {
      u_int8_t  nexthdr;
      u_int8_t  hdrlen;       /* This one is measured in 32 bit units! */
      u_int16_t reserved;
      u_int32_t spi;
      u_int32_t seq_no;       /* Sequence number */
      u_int8_t  auth_data[0]; /* Variable len but &gt;=4. Mind the
                                 64 bit alignment! */
    #define icv     auth_data       /* rfc 4302 name */
      /* TBD - high-order sequence number */
  
    };
  
   /*
    * encapsulated security payload header
    */
    struct ip_esp_hdr {
      u_int32_t spi;
      u_int32_t seq_no;       /* Sequence number */
      u_int8_t  enc_data[0];  /* Variable len but &gt;=8. Mind the
                              64 bit alignment! */  
    };
  </code></pre>
  
  <p>If anyone getting any clue where is the leakage going on ??? and how to patch it ??</p>