Upgrade to tcpdump 4.9.0.

From CHANGES:

  Wednesday January 18, 2017 devel.fx.lebail@orange.fr
  Summary for 4.9.0 tcpdump release
    General updates:
    Improve separation frontend/backend (tcpdump/libnetdissect)
    Don't require IPv6 library support in order to support IPv6 addresses
    Introduce data types to use for integral values in packet structures
    Fix display of timestamps with -tt, -ttt and -ttttt options
    Fix some heap overflows found with American Fuzzy Lop by Hanno Boeck and others
        (More information in the log with CVE-2016-* and CVE-2017-*)
    Change the way protocols print link-layer addresses (Fix heap overflows
        in CALM-FAST and GeoNetworking printers)
    Pass correct caplen value to ether_print() and some other functions
    Fix lookup_nsap() to match what isonsap_string() expects
    Clean up relative time stamp printing (Fix an array overflow)
    Fix some alignment issues with GCC on Solaris 10 SPARC
    Add some ND_TTEST_/ND_TCHECK_ macros to simplify writing bounds checks
    Add a fn_printztn() which returns the number of bytes processed
    Add nd_init() and nd_cleanup() functions. Improve libsmi support
    Add CONTRIBUTING file
    Add a summary comment in all printers
    Compile with more warning options in devel mode if supported (-Wcast-qual, ...)
    Fix some leaks found by Valgrind/Memcheck
    Fix a bunch of de-constifications
    Squelch some Coverity warnings and some compiler warnings
    Update Coverity and Travis-CI setup
    Update Visual Studio files

    Frontend:
    Fix capsicum support to work with zerocopy buffers in bpf
    Try opening interfaces by name first, then by name-as-index
    Work around pcap_create() failures fetching time stamp type lists
    Fix a segmentation fault with 'tcpdump -J'
    Improve addrtostr6() bounds checking
    Add exit_tcpdump() function
    Don't drop CAP_SYS_CHROOT before chrooting
    Fixes issue where statistics not reported when -G and -W options used

    New printers supporting:
    Generic Protocol Extension for VXLAN (VXLAN-GPE)
    Home Networking Control Protocol (HNCP), RFCs 7787 and 7788
    Locator/Identifier Separation Protocol (LISP), type 3 and type 4 packets
    Marvell Extended Distributed Switch Architecture header (MEDSA)
    Network Service Header (NSH)
    REdis Serialization Protocol (RESP)

    Updated printers:
    802.11: Beginnings of 11ac radiotap support
    802.11: Check the Protected bit for management frames
    802.11: Do bounds checking on last_presentp before dereferencing it (Fix a heap overflow)
    802.11: Fix the radiotap printer to handle the special bits correctly
    802.11: If we have the MCS field, it's 11n
    802.11: Only print unknown frame type or subtype messages once
    802.11: Radiotap dBm values get printed as dB; Update a test output accordingly
    802.11: Source and destination addresses were backwards
    AH: Add a bounds check
    AH: Report to our caller that dissection failed if a bounds check fails
    AP1394: Print src > dst, not dst > src
    ARP: Don't assume the target hardware address is <= 6 octets long (Fix a heap overflow)
    ATALK: Add bounds and length checks (Fix heap overflows)
    ATM: Add some bounds checks (Fix a heap overflow)
    ATM: Fix an incorrect bounds check
    BFD: Update specification from draft to RFC 5880
    BFD: Update to print optional authentication field
    BGP: Add decoding of ADD-PATH capability
    BGP: Add support for the AIGP attribute (RFC7311)
    BGP: Print LARGE_COMMUNITY Path Attribute
    BGP: Update BGP numbers from IANA; Print minor values for FSM notification
    BOOTP: Add a bounds check
    Babel: Add decoder for source-specific extension
    CDP: Filter out non-printable characters
    CFM: Fixes to match the IEEE standard, additional bounds and length checks
    CSLIP: Add more bounds checks (Fix a heap overflow)
    ClassicalIPoATM: Add a bounds check on LLC+SNAP header (Fix a heap overflow)
    DHCP: Fix MUDURL and TZ options
    DHCPv6: Process MUDURL and TZ options
    DHCPv6: Update Status Codes with RFCs/IANA names
    DNS: Represent the "DNSSEC OK" bit as "DO" instead of "OK". Add a test case
    DTP: Improve packet integrity checks
    EGP: Fix bounds checks
    ESP: Don't use OpenSSL_add_all_algorithms() in OpenSSL 1.1.0 or later
    ESP: Handle OpenSSL 1.1.x
    Ethernet: Add some bounds checking before calling isoclns_print (Fix a heap overflow)
    Ethernet: Print the Length/Type field as length when needed
    FDDI: Fix -e output for FDDI
    FR: Add some packet-length checks and improve Q.933 printing (Fix heap overflows)
    GRE: Add some bounds checks (Fix heap overflows)
    Geneve: Fix error message with invalid option length; Update list option classes
    HNCP: Fix incorrect time interval format. Fix handling of IPv4 prefixes
    ICMP6: Fetch a 32-bit big-endian quantity with EXTRACT_32BITS()
    ICMP6: dagid is always an IPv6 address, not an opaque 128-bit string
    IGMP: Add a length check
    IP: Add a bounds check (Fix a heap overflow)
    IP: Check before fetching the protocol version (Fix a heap overflow)
    IP: Don't try to dissect if IP version != 4 (Fix a heap overflow)
    IP: Stop processing IPPROTO_ values once we hit IPPROTO_IPCOMP
    IPComp: Check whether we have the CPI before we fetch it (Fix a heap overflow)
    IPoFC: Fix -e output (IP-over-Fibre Channel)
    IPv6: Don't overwrite the destination IPv6 address for routing headers
    IPv6: Fix header printing
    IPv6: Stop processing IPPROTO_ values once we hit IPPROTO_IPCOMP
    ISAKMP: Clean up parsing of IKEv2 Security Associations
    ISOCLNS/IS-IS: Add support for Purge Originator Identifier (RFC6232) and test cases
    ISOCLNS/IS-IS: Don't overwrite packet data when checking the signature
    ISOCLNS/IS-IS: Filter out non-printable characters
    ISOCLNS/IS-IS: Fix segmentation faults
    ISOCLNS/IS-IS: Have signature_verify() do the copying and clearing
    ISOCLNS: Add some bounds checks
    Juniper: Make sure a Juniper header TLV isn't bigger than what's left in the packet (Fix a heap overflow)
    LLC/SNAP: With -e, print the LLC header before the SNAP header; without it, cut the SNAP header
    LLC: Add a bounds check (Fix a heap overflow)
    LLC: Clean up printing of LLC packets
    LLC: Fix the printing of RFC 948-style IP packets
    LLC: Skip the LLC and SNAP headers with -x for 802.11 and some other protocols
    LLDP: Implement IANA OUI and LLDP MUD option
    MPLS LSP ping: Update printing for RFC 4379, bug fixes, more bounds checks
    MPLS: "length" is now the *remaining* packet length
    MPLS: Add bounds and length checks (Fix a heap overflow)
    NFS: Add a test that makes unaligned accesses
    NFS: Don't assume the ONC RPC header is nicely aligned
    NFS: Don't overflow the Opaque_Handle buffer (Fix a segmentation fault)
    NFS: Don't run past the end of an NFSv3 file handle
    OLSR: Add a test to cover a HNA sgw case
    OLSR: Fix 'Advertised networks' count
    OLSR: Fix printing of smart-gateway HNAs in IPv4
    OSPF: Add a bounds check for the Hello packet options
    OSPF: Do more bounds checking
    OSPF: Fix a segmentation fault
    OSPF: Fix printing 'ospf_topology_values' default
    OTV: Add missing bounds checks
    PGM: Print the formatted IP address, not the raw binary address, as a string
    PIM: Add some bounds checking (Fix a heap overflow)
    PIMv2: Fix checksumming of Register messages
    PPI: Pass an adjusted struct pcap_pkthdr to the sub-printer
    PPP: Add some bounds checks (Fix a heap overflow)
    PPP: Report invalid PAP AACK/ANAK packets
    Q.933: Add a missing bounds check
    RADIUS: Add Value 13 "VLAN" to Tunnel-Type attribute
    RADIUS: Filter out non-printable characters
    RADIUS: Translate UDP/1700 as RADIUS
    RESP: Do better checking of RESP packets
    RPKI-RTR: Add a return value check for "fn_printn" call
    RPKI-RTR: Remove printing when truncated condition already detected
    RPL: Fix 'Consistency Check' control code
    RPL: Fix suboption print
    RSVP: An INTEGRITY object in a submessage covers only the submessage
    RSVP: Fix an infinite loop; Add bounds and length checks
    RSVP: Fix some if statements missing brackets
    RSVP: Have signature_verify() do the copying and clearing
    RTCP: Add some bounds checks
    RTP: Add some bounds checks, fix two segmentation faults
    SCTP: Do more bounds checking
    SFLOW: Fix bounds checking
    SLOW: Fix bugs, add checks
    SMB: Before fetching the flags2 field, make sure we have it
    SMB: Do bounds checks on NBNS resource types and resource data lengths
    SNMP: Clean up the "have libsmi but no modules loaded" case
    SNMP: Clean up the object abbreviation list and fix the code to match them
    SNMP: Do bounds checks when printing character and octet strings
    SNMP: Improve ASN.1 bounds checks
    SNMP: More bounds and length checks
    STP: Add a bunch of bounds checks, and fix some printing (Fix heap overflows)
    STP: Filter out non-printable characters
    TCP: Add bounds and length checks for packets with TCP option 20
    TCP: Correct TCP option Kind value for TCP Auth and add SCPS-TP
    TCP: Fix two bounds checks (Fix heap overflows)
    TCP: Make sure we have the data offset field before fetching it (Fix a heap overflow)
    TCP: Put TCP-AO option decoding right
    TFTP: Don't use strchr() to scan packet data (Fix a heap overflow)
    Telnet: Add some bounds checks
    TokenRing: Fix -e output
    UDLD: Fix an infinite loop
    UDP: Add a bounds check (Fix a heap overflow)
    UDP: Check against the packet length first
    UDP: Don't do the DDP-over-UDP heuristic check up front
    VAT: Add some bounds checks
    VTP: Add a test on Mgmt Domain Name length
    VTP: Add bounds checks and filter out non-printable characters
    VXLAN: Add a bound check and a test case
    ZeroMQ: Fix an infinite loop

  Tuesday April 14, 2015 guy@alum.mit.edu
  Summary for 4.8.0 tcpdump release
        Fix "-x" for Apple PKTAP and PPI packets

Bug: N/A
Test: "adb shell tcpdump"
Change-Id: I81df72cf1ebdbe61c5b6069d8532ae817570f23f
diff --git a/print-sctp.c b/print-sctp.c
index 4b595f2..f625dce 100644
--- a/print-sctp.c
+++ b/print-sctp.c
@@ -33,20 +33,19 @@
  * SUCH DAMAGE.
  */
 
-#define NETDISSECT_REWORKED
+/* \summary: Stream Control Transmission Protocol (SCTP) printer */
+
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
 
-#include <tcpdump-stdinc.h>
+#include <netdissect-stdinc.h>
 
-#include "interface.h"
+#include "netdissect.h"
 #include "addrtoname.h"
-#include "extract.h"			/* must come after interface.h */
+#include "extract.h"
 #include "ip.h"
-#ifdef INET6
 #include "ip6.h"
-#endif
 
 /* Definitions from:
  *
@@ -496,48 +495,35 @@
                 const u_char *bp2,       /* beginning of enclosing */
                 u_int sctpPacketLength)  /* ip packet */
 {
+  u_int sctpPacketLengthRemaining;
   const struct sctpHeader *sctpPktHdr;
   const struct ip *ip;
-#ifdef INET6
   const struct ip6_hdr *ip6;
-#endif
-  const void *endPacketPtr;
   u_short sourcePort, destPort;
   int chunkCount;
   const struct sctpChunkDesc *chunkDescPtr;
-  const void *nextChunk;
   const char *sep;
   int isforces = 0;
 
-
-  sctpPktHdr = (const struct sctpHeader*) bp;
-  endPacketPtr = (const u_char*)sctpPktHdr+sctpPacketLength;
-
-  if( (u_long) endPacketPtr > (u_long) ndo->ndo_snapend)
-    endPacketPtr = (const void *) ndo->ndo_snapend;
-  ip = (struct ip *)bp2;
-#ifdef INET6
-  if (IP_V(ip) == 6)
-    ip6 = (const struct ip6_hdr *)bp2;
-  else
-    ip6 = NULL;
-#endif /*INET6*/
-  ND_TCHECK(*sctpPktHdr);
-
   if (sctpPacketLength < sizeof(struct sctpHeader))
     {
       ND_PRINT((ndo, "truncated-sctp - %ld bytes missing!",
-		   (long)sctpPacketLength-sizeof(struct sctpHeader)));
+		   (long)(sizeof(struct sctpHeader) - sctpPacketLength)));
       return;
     }
-
-  /*    sctpPacketLength -= sizeof(struct sctpHeader);  packet length  */
-  /*  			      is now only as long as the payload  */
+  sctpPktHdr = (const struct sctpHeader*) bp;
+  ND_TCHECK(*sctpPktHdr);
+  sctpPacketLengthRemaining = sctpPacketLength;
 
   sourcePort = EXTRACT_16BITS(&sctpPktHdr->source);
   destPort = EXTRACT_16BITS(&sctpPktHdr->destination);
 
-#ifdef INET6
+  ip = (const struct ip *)bp2;
+  if (IP_V(ip) == 6)
+    ip6 = (const struct ip6_hdr *)bp2;
+  else
+    ip6 = NULL;
+
   if (ip6) {
     ND_PRINT((ndo, "%s.%d > %s.%d: sctp",
       ip6addr_string(ndo, &ip6->ip6_src),
@@ -545,7 +531,6 @@
       ip6addr_string(ndo, &ip6->ip6_dst),
       destPort));
   } else
-#endif /*INET6*/
   {
     ND_PRINT((ndo, "%s.%d > %s.%d: sctp",
       ipaddr_string(ndo, &ip->ip_src),
@@ -563,40 +548,48 @@
          isforces = 1;
   }
 
+  bp += sizeof(struct sctpHeader);
+  sctpPacketLengthRemaining -= sizeof(struct sctpHeader);
+
   if (ndo->ndo_vflag >= 2)
     sep = "\n\t";
   else
     sep = " (";
   /* cycle through all chunks, printing information on each one */
-  for (chunkCount = 0,
-	 chunkDescPtr = (const struct sctpChunkDesc *)
-	    ((const u_char*) sctpPktHdr + sizeof(struct sctpHeader));
-       chunkDescPtr != NULL &&
-	 ( (const void *)
-	    ((const u_char *) chunkDescPtr + sizeof(struct sctpChunkDesc))
-	   <= endPacketPtr);
-
-       chunkDescPtr = (const struct sctpChunkDesc *) nextChunk, chunkCount++)
+  for (chunkCount = 0, chunkDescPtr = (const struct sctpChunkDesc *)bp;
+      sctpPacketLengthRemaining != 0;
+      chunkCount++)
     {
-      uint16_t chunkLength;
-      const u_char *chunkEnd;
+      uint16_t chunkLength, chunkLengthRemaining;
       uint16_t align;
 
+      chunkDescPtr = (const struct sctpChunkDesc *)bp;
+      if (sctpPacketLengthRemaining < sizeof(*chunkDescPtr)) {
+        ND_PRINT((ndo, "%s%d) [chunk descriptor cut off at end of packet]", sep, chunkCount+1));
+        break;
+      }
       ND_TCHECK(*chunkDescPtr);
       chunkLength = EXTRACT_16BITS(&chunkDescPtr->chunkLength);
       if (chunkLength < sizeof(*chunkDescPtr)) {
-        ND_PRINT((ndo, "%s%d) [Bad chunk length %u]", sep, chunkCount+1, chunkLength));
+        ND_PRINT((ndo, "%s%d) [Bad chunk length %u, < size of chunk descriptor]", sep, chunkCount+1, chunkLength));
         break;
       }
+      chunkLengthRemaining = chunkLength;
 
-      ND_TCHECK2(*((uint8_t *)chunkDescPtr), chunkLength);
-      chunkEnd = ((const u_char*)chunkDescPtr + chunkLength);
-
-      align=chunkLength % 4;
+      align = chunkLength % 4;
       if (align != 0)
 	align = 4 - align;
 
-      nextChunk = (const void *) (chunkEnd + align);
+      if (sctpPacketLengthRemaining < align) {
+        ND_PRINT((ndo, "%s%d) [Bad chunk length %u, > remaining data in packet]", sep, chunkCount+1, chunkLength));
+        break;
+      }
+
+      ND_TCHECK2(*bp, chunkLength);
+
+      bp += sizeof(*chunkDescPtr);
+      sctpPacketLengthRemaining -= sizeof(*chunkDescPtr);
+      chunkLengthRemaining -= sizeof(*chunkDescPtr);
 
       ND_PRINT((ndo, "%s%d) ", sep, chunkCount+1));
       ND_PRINT((ndo, "[%s] ", tok2str(sctp_chunkid_str, "Unknown chunk type: 0x%x",
@@ -607,7 +600,6 @@
 	  {
 	    const struct sctpDataPart *dataHdrPtr;
 	    uint32_t ppid;
-	    const u_char *payloadPtr;
 	    u_int payload_size;
 
 	    if ((chunkDescPtr->chunkFlg & SCTP_DATA_UNORDERED)
@@ -632,7 +624,11 @@
 		 == SCTP_DATA_LAST_FRAG) )
 	      ND_PRINT((ndo, " "));
 
-	    dataHdrPtr=(const struct sctpDataPart*)(chunkDescPtr+1);
+	    if (chunkLengthRemaining < sizeof(*dataHdrPtr)) {
+		ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
+		return;
+	    }
+	    dataHdrPtr=(const struct sctpDataPart*)bp;
 
 	    ppid = EXTRACT_32BITS(&dataHdrPtr->payloadtype);
 	    ND_PRINT((ndo, "[TSN: %u] ", EXTRACT_32BITS(&dataHdrPtr->TSN)));
@@ -647,70 +643,92 @@
 		    (ppid == SCTP_PPID_FORCES_LP);
 	    }
 
-	    payloadPtr = (const u_char *) (dataHdrPtr + 1);
-	    if (EXTRACT_16BITS(&chunkDescPtr->chunkLength) <
-		    sizeof(struct sctpDataPart) + sizeof(struct sctpChunkDesc) + 1) {
-		ND_PRINT((ndo, "bogus chunk length %u]", EXTRACT_16BITS(&chunkDescPtr->chunkLength)));
+	    bp += sizeof(*dataHdrPtr);
+	    sctpPacketLengthRemaining -= sizeof(*dataHdrPtr);
+	    chunkLengthRemaining -= sizeof(*dataHdrPtr);
+	    payload_size = chunkLengthRemaining;
+	    if (payload_size == 0) {
+		ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
 		return;
 	    }
 
-	    payload_size = EXTRACT_16BITS(&chunkDescPtr->chunkLength) -
-		(sizeof(struct sctpDataPart) + sizeof(struct sctpChunkDesc));
-
 	    if (isforces) {
-		forces_print(ndo, payloadPtr, payload_size);
+		forces_print(ndo, bp, payload_size);
 	    } else if (ndo->ndo_vflag >= 2) {	/* if verbose output is specified */
 					/* at the command line */
 		switch (ppid) {
 		case SCTP_PPID_M3UA :
-			m3ua_print(ndo, payloadPtr, payload_size);
+			m3ua_print(ndo, bp, payload_size);
 			break;
 		default:
 			ND_PRINT((ndo, "[Payload"));
 			if (!ndo->ndo_suppress_default_print) {
 				ND_PRINT((ndo, ":"));
-				ND_DEFAULTPRINT(payloadPtr, payload_size);
+				ND_DEFAULTPRINT(bp, payload_size);
 			}
 			ND_PRINT((ndo, "]"));
 			break;
 		}
 	    }
+	    bp += payload_size;
+	    sctpPacketLengthRemaining -= payload_size;
+	    chunkLengthRemaining -= payload_size;
 	    break;
 	  }
 	case SCTP_INITIATION :
 	  {
 	    const struct sctpInitiation *init;
 
-	    init=(const struct sctpInitiation*)(chunkDescPtr+1);
+	    if (chunkLengthRemaining < sizeof(*init)) {
+		ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
+		return;
+	    }
+	    init=(const struct sctpInitiation*)bp;
 	    ND_PRINT((ndo, "[init tag: %u] ", EXTRACT_32BITS(&init->initTag)));
 	    ND_PRINT((ndo, "[rwnd: %u] ", EXTRACT_32BITS(&init->rcvWindowCredit)));
 	    ND_PRINT((ndo, "[OS: %u] ", EXTRACT_16BITS(&init->NumPreopenStreams)));
 	    ND_PRINT((ndo, "[MIS: %u] ", EXTRACT_16BITS(&init->MaxInboundStreams)));
 	    ND_PRINT((ndo, "[init TSN: %u] ", EXTRACT_32BITS(&init->initialTSN)));
+	    bp += sizeof(*init);
+ 	    sctpPacketLengthRemaining -= sizeof(*init);
+	    chunkLengthRemaining -= sizeof(*init);
 
-#if(0) /* ALC you can add code for optional params here */
-	    if( (init+1) < chunkEnd )
+#if 0 /* ALC you can add code for optional params here */
+	    if( chunkLengthRemaining != 0 )
 	      ND_PRINT((ndo, " @@@@@ UNFINISHED @@@@@@%s\n",
 		     "Optional params present, but not printed."));
 #endif
+            bp += chunkLengthRemaining;
+	    sctpPacketLengthRemaining -= chunkLengthRemaining;
+            chunkLengthRemaining = 0;
 	    break;
 	  }
 	case SCTP_INITIATION_ACK :
 	  {
 	    const struct sctpInitiation *init;
 
-	    init=(const struct sctpInitiation*)(chunkDescPtr+1);
+	    if (chunkLengthRemaining < sizeof(*init)) {
+		ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
+		return;
+	    }
+	    init=(const struct sctpInitiation*)bp;
 	    ND_PRINT((ndo, "[init tag: %u] ", EXTRACT_32BITS(&init->initTag)));
 	    ND_PRINT((ndo, "[rwnd: %u] ", EXTRACT_32BITS(&init->rcvWindowCredit)));
 	    ND_PRINT((ndo, "[OS: %u] ", EXTRACT_16BITS(&init->NumPreopenStreams)));
 	    ND_PRINT((ndo, "[MIS: %u] ", EXTRACT_16BITS(&init->MaxInboundStreams)));
 	    ND_PRINT((ndo, "[init TSN: %u] ", EXTRACT_32BITS(&init->initialTSN)));
+            bp += sizeof(*init);
+            sctpPacketLengthRemaining -= sizeof(*init);
+            chunkLengthRemaining -= sizeof(*init);
 
-#if(0) /* ALC you can add code for optional params here */
-	    if( (init+1) < chunkEnd )
+#if 0 /* ALC you can add code for optional params here */
+	    if( chunkLengthRemaining != 0 )
 	      ND_PRINT((ndo, " @@@@@ UNFINISHED @@@@@@%s\n",
 		     "Optional params present, but not printed."));
 #endif
+            bp += chunkLengthRemaining;
+	    sctpPacketLengthRemaining -= chunkLengthRemaining;
+            chunkLengthRemaining = 0;
 	    break;
 	  }
 	case SCTP_SELECTIVE_ACK:
@@ -720,38 +738,77 @@
 	    int fragNo, tsnNo;
 	    const u_char *dupTSN;
 
-	    sack=(const struct sctpSelectiveAck*)(chunkDescPtr+1);
+	    if (chunkLengthRemaining < sizeof(*sack)) {
+	      ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
+	      return;
+	    }
+	    sack=(const struct sctpSelectiveAck*)bp;
 	    ND_PRINT((ndo, "[cum ack %u] ", EXTRACT_32BITS(&sack->highestConseqTSN)));
 	    ND_PRINT((ndo, "[a_rwnd %u] ", EXTRACT_32BITS(&sack->updatedRwnd)));
 	    ND_PRINT((ndo, "[#gap acks %u] ", EXTRACT_16BITS(&sack->numberOfdesc)));
 	    ND_PRINT((ndo, "[#dup tsns %u] ", EXTRACT_16BITS(&sack->numDupTsns)));
+            bp += sizeof(*sack);
+	    sctpPacketLengthRemaining -= sizeof(*sack);
+            chunkLengthRemaining -= sizeof(*sack);
 
 
 	    /* print gaps */
-	    for (frag = ( (const struct sctpSelectiveFrag *)
-			  ((const struct sctpSelectiveAck *) sack+1)),
-		   fragNo=0;
-		 (const void *)frag < nextChunk && fragNo < EXTRACT_16BITS(&sack->numberOfdesc);
-		 frag++, fragNo++)
+	    for (fragNo=0;
+		 chunkLengthRemaining != 0 && fragNo < EXTRACT_16BITS(&sack->numberOfdesc);
+		 bp += sizeof(*frag), sctpPacketLengthRemaining -= sizeof(*frag), chunkLengthRemaining -= sizeof(*frag), fragNo++) {
+	      if (chunkLengthRemaining < sizeof(*frag)) {
+		ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
+		return;
+	      }
+	      frag = (const struct sctpSelectiveFrag *)bp;
 	      ND_PRINT((ndo, "\n\t\t[gap ack block #%d: start = %u, end = %u] ",
 		     fragNo+1,
 		     EXTRACT_32BITS(&sack->highestConseqTSN) + EXTRACT_16BITS(&frag->fragmentStart),
 		     EXTRACT_32BITS(&sack->highestConseqTSN) + EXTRACT_16BITS(&frag->fragmentEnd)));
-
+	    }
 
 	    /* print duplicate TSNs */
-	    for (dupTSN = (const u_char *)frag, tsnNo=0;
-		 (const void *) dupTSN < nextChunk && tsnNo<EXTRACT_16BITS(&sack->numDupTsns);
-		 dupTSN += 4, tsnNo++)
+	    for (tsnNo=0;
+		 chunkLengthRemaining != 0 && tsnNo<EXTRACT_16BITS(&sack->numDupTsns);
+		 bp += 4, sctpPacketLengthRemaining -= 4, chunkLengthRemaining -= 4, tsnNo++) {
+	      if (chunkLengthRemaining < 4) {
+		ND_PRINT((ndo, "bogus chunk length %u]", chunkLength));
+		return;
+	      }
+              dupTSN = (const u_char *)bp;
 	      ND_PRINT((ndo, "\n\t\t[dup TSN #%u: %u] ", tsnNo+1,
-	          EXTRACT_32BITS(dupTSN)));
-
+	        EXTRACT_32BITS(dupTSN)));
+	    }
+	    break;
+	  }
+	default :
+	  {
+            bp += chunkLengthRemaining;
+            sctpPacketLengthRemaining -= chunkLengthRemaining;
+            chunkLengthRemaining = 0;
 	    break;
 	  }
 	}
 
-	if (ndo->ndo_vflag < 2)
-	  sep = ", (";
+      /*
+       * Any extra stuff at the end of the chunk?
+       * XXX - report this?
+       */
+      bp += chunkLengthRemaining;
+      sctpPacketLengthRemaining -= chunkLengthRemaining;
+
+      if (ndo->ndo_vflag < 2)
+        sep = ", (";
+
+      if (align != 0) {
+	/*
+	 * Fail if the alignment padding isn't in the captured data.
+	 * Otherwise, skip it.
+	 */
+	ND_TCHECK2(*bp, align);
+	bp += align;
+	sctpPacketLengthRemaining -= align;
+      }
     }
     return;