Home
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running QNX Neutrino 7.1.
Utilities & Libraries
C Library Reference
I
inet6_rthdr_segments()
Count the segments in an IPv6 routing header

QNX Momentics IDE User's Guide
This User's Guide describes version 7.1 of the Integrated Development Environment (IDE) that's part of the QNX Momentics tool suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running QNX Neutrino 7.1.
- Quickstart Guide
- OS Components & Operations
- Audio & Graphics API
- Multimedia
- Networking Middleware
- Programming
- Sensor Framework
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX Neutrino RTOS system and developers who want to create a QNX Neutrino resource manager free from vulnerabilities.
- Utilities & Libraries
  - Addon Interfaces Library Reference
  - C Library Reference
    - What's in a Function Description?
    - Manifests
    - Character Sets
    - A
    - B
    - C
    - D
    - E
    - F
    - G
    - H
    - I
      - ICMP
        Internet Control Message Protocol
      - ICMP6
        Internet Control Message Protocol for IP6
      - if_freenameindex()
        Free dynamic memory allocated by if_nameindex()
      - if_indextoname()
        Map an interface index to its name
      - if_nameindex()
        Return a list of interfaces
      - if_nametoindex()
        Map an interface name to its index
      - ifaddrs
        Structure that describes an Internet host
      - ilogb(), ilogbf(), ilogbl()
        Compute the integral part of a logarithm
      - in8()
        Read an 8-bit value from a port
      - in8s()
        Read 8-bit values from a port
      - in16(), inbe16(), inle16()
        Read a 16-bit value from a port
      - in16s()
        Read 16-bit values from a port
      - in32(), inbe32(), inle32()
        Read a 32-bit value from a port
      - in32s()
        Read 32-bit values from a port
      - index()
        Find a character in a string
      - inet_addr()
        Convert a string into a numeric Internet address
      - inet_aton()
        Convert a string into an Internet address stored in a structure
      - inet_lnaof()
        Extract the local network address from an Internet address
      - inet_makeaddr()
        Convert a network number and a local network address into an Internet address
      - inet_net_ntop()
        Convert an Internet network number to CIDR format
      - inet_netof()
        Extract the network number from an Internet address
      - inet_net_pton()
        Convert an Internet network number from CIDR format to network format
      - inet_network()
        Convert a string into an Internet network number
      - inet_ntoa()
        Convert an Internet address into a string
      - inet_ntoa_r()
        Convert an Internet address into a string
      - inet_ntop()
        Convert a numeric network address to a string
      - inet_pton()
        Convert a text host address to a numeric address
      - INET6
        Internet protocol version 6 family
      - inet6_option_alloc()
        Append IPv6 hop-by-hop or destination options into ancillary data object
      - inet6_option_append()
        Append an IPv6 hop-by-hop or destination option to an ancillary data object
      - inet6_option_find()
        Search for IPv6 hop-by-hop and destination options
      - inet6_option_init()
        Initialize an ancillary data object that contains IPv6 hop-by-hop and destination options
      - inet6_option_next()
        Find the next IPv6 hop-by-hop or destination option
      - inet6_option_space()
        Determine how much space an IPv6 hop-by-hop or destination option requires
      - inet6_rthdr_add()
        Add an address to an IPv6 routing header
      - inet6_rthdr_getaddr()
        Get a pointer to an IPv6 address in the routing header
      - inet6_rthdr_getflags()
        Get the flags for a segment in an IPv6 routing header
      - inet6_rthdr_init()
        Initialize an IPv6 routing header
      - inet6_rthdr_lasthop()
        Specify the Strict/Loose flag for the final hop of an IPv6 routing header
      - inet6_rthdr_reverse()
        Reverse the list of addresses in an IPv6 router header
      - inet6_rthdr_segments()
        Count the segments in an IPv6 routing header
      - inet6_rthdr_space()
        Determine the space required by an IPv6 routing header
      - initgroups()
        Initialize the supplementary group access list
      - initstate()
        Initialize a pseudo-random number generator
      - inotify_add_watch()
        Add or update a watch for filesystem events associated with a path
      - inotify_event
        Structure that describes a watched filesystem event
      - inotify_init()
        Initialize the inode notify system
      - inotify_rm_watch()
        Remove the watch associated with the given watch descriptor
      - inotify_qnx_ext()
        Enable QNX Neutrino-specific extensions to the inotify interface
      - insque()
        Insert an element into a doubly linked queue
      - InterruptAttach(), InterruptAttach_r()
        Attach an Interrupt Service Routine (ISR) to an interrupt source
      - InterruptAttachArray(), InterruptAttachArray_r()
        Attach an Interrupt Service Routine (ISR) that returns an array of sigevents to an interrupt source
      - InterruptAttachEvent(), InterruptAttachEvent_r()
        Attach an event to an interrupt source
      - InterruptDetach(), InterruptDetach_r()
        Detach an interrupt handler by ID
      - InterruptDisable()
        Disable hardware interrupts
      - InterruptEnable()
        Enable hardware interrupts
      - InterruptHookIdle2()
        Attach an idle interrupt handler
      - InterruptHookTrace()
        Attach the pseudo interrupt handler that the instrumented module uses
      - InterruptLock()
        Guard a critical section in an interrupt handler
      - InterruptMask()
        Disable a hardware interrupt
      - InterruptStatus()
        Determine whether or not interrupts are enabled
      - InterruptUnlock()
        Release a critical section in an interrupt handler
      - InterruptUnmask()
        Enable a hardware interrupt
      - InterruptWait(), InterruptWait_r()
        Wait for a hardware interrupt
      - _io_connect
        Structure of a resource manager's connect message
      - _io_connect_ftype_reply
        Structure of a connect message giving a status and a file type
      - _io_connect_link_reply
        Structure of a connect message that redirects a client to another resource
      - ioctl(), vioctl()
        Control a device
      - iofdinfo()
        Retrieve server attributes
      - iofunc_ability_check()
        Verify that the client has a given resource manager ability
      - iofunc_acl()
        Handle an _IO_ACL message
      - iofunc_acl_default()
        Default handler for the acl callout
      - iofunc_attr_init(), iofunc_attr_init_sized()
        Initialize the per-name attribute structure associated with a device
      - iofunc_attr_lock()
        Lock the attribute structure
      - iofunc_attr_t
        I/O attribute structure
      - iofunc_attr_trylock()
        Try to lock the attribute structure
      - iofunc_attr_unlock()
        Unlock the attribute structure
      - iofunc_check_access()
        Check access permissions
      - iofunc_chmod()
        Handle an _IO_CHMOD message
      - iofunc_chmod_default()
        Default handler for _IO_CHMOD messages
      - iofunc_chown()
        Handle an _IO_CHOWN message
      - iofunc_chown_default()
        Default handler for _IO_CHOWN messages
      - iofunc_client_info_able()
        Return information about a client connection, including abilities
      - iofunc_client_info_ext()
        Return information about a client connection
      - iofunc_client_info_ext_free()
        Free the structure used for information about a client connection
      - iofunc_close_dup()
        Free all locks allocated for the client process
      - iofunc_close_dup_default()
        Default handler for _IO_CLOSE messages
      - iofunc_close_ocb()
        Return the memory allocated for an OCB
      - iofunc_close_ocb_default()
        Return the memory allocated for an OCB
      - iofunc_devctl()
        Handle an _IO_DEVCTL message
      - iofunc_devctl_default()
        Default handler for _IO_DEVCTL messages
      - iofunc_devctl_verify()
        Perform validation that's common to all handlers for _IO_DEVCTL messages
      - iofunc_fdinfo()
        Handle an _IO_FDINFO message
      - iofunc_fdinfo_default()
        Default handler for _IO_FDINFO messages
      - iofunc_func_init()
        Initialize the default POSIX-layer function tables
      - iofunc_link()
        Link two directory entries
      - iofunc_lock()
        Lock a resource
      - iofunc_lock_calloc()
        Allocate memory to lock structures
      - iofunc_lock_default()
        Default handler for _IO_LOCK messages
      - iofunc_lock_free()
        Return memory allocated for lock structures
      - iofunc_lock_ocb_default()
        Default handler for the lock_ocb callout
      - iofunc_lseek()
        Handle an _IO_LSEEK message
      - iofunc_lseek_default()
        Default handler for _IO_LSEEK messages
      - iofunc_mknod()
        Verify a client's ability to make a new filesystem entry point
      - iofunc_mmap()
        Handle an _IO_MMAP message
      - iofunc_mmap_default(), iofunc_mmap_default_ext()
        Default handler for _IO_MMAP messages
      - iofunc_mmap_ext()
        Handle an _IO_MMAP message
      - iofunc_mount_fini()
        Clean up the IOFUNC_MOUNT_T structure
      - iofunc_mount_init()
        Initialize the IOFUNC_MOUNT_T structure
      - iofunc_mount_set_time()
        Set the timestamp resolution for iofunc functions and structures
      - iofunc_mount_t
        I/O mount structure
      - iofunc_notify()
        Add, poll, or remove a notification handler
      - iofunc_notify_remove(), iofunc_notify_remove_strict()
        Remove notification entries from a list
      - iofunc_notify_trigger(), iofunc_notify_trigger_strict()
        Send notifications to queued clients
      - iofunc_ocb_attach()
        Initialize an Open Control Block
      - iofunc_ocb_calloc()
        Allocate an iofunc Open Control Block
      - iofunc_ocb_detach()
        Release Open Control Block resources
      - iofunc_ocb_free()
        Deallocate an iofunc Open Control Block's memory
      - iofunc_ocb_t
        Open Control Block structure
      - iofunc_open()
        Verify a client's ability to open or to create a resource
      - iofunc_open_default()
        Default handler for _IO_CONNECT messages
      - iofunc_openfd()
        Increment count and locking flags
      - iofunc_openfd_default()
        Default handler for _IO_OPENFD messages
      - iofunc_pathconf()
        Support pathconf() requests
      - iofunc_pathconf_default()
        Default handler for _IO_PATHCONF messages
      - iofunc_read_default()
        Default handler for _IO_READ messages
      - iofunc_read_verify()
        Verify a client's read access to a resource
      - iofunc_readlink()
        Verify the attributes being used to read a link
      - iofunc_rename()
        Do permission checks for a _IO_CONNECT_RENAME message
      - iofunc_space_verify()
        Do permission checks for the _IO_SPACE message
      - iofunc_stat(), iofunc_stat_format()
        Populate a stat structure
      - iofunc_stat_default()
        Default handler for _IO_STAT messages
      - iofunc_sync()
        Indicate if synchronization is needed
      - iofunc_sync_default()
        Default handler for _IO_SYNC messages
      - iofunc_sync_verify()
        Verify permissions to sync
      - iofunc_time_update()
        Update time stamps
      - iofunc_unblock()
        Unblock OCBs
      - iofunc_unblock_default()
        Default unblock handler
      - iofunc_unlink()
        Verify that an entry can be unlinked
      - iofunc_unlock_ocb_default()
        Default handler for the unlock_ocb callout
      - iofunc_utime()
        Update time stamps
      - iofunc_utime_default()
        Default handler for _IO_UTIME messages
      - iofunc_write_default()
        Default handler for _IO_WRITE messages
      - iofunc_write_verify()
        Verify a client's write access to a resource
      - ionotify()
        Arm a resource manager
      - IP
        Internet Protocol
      - IPsec
        Internet security protocol
      - ipsec_dump_policy()
        Generate a readable string from an IPsec policy specification
      - ipsec_get_policylen()
        Get the length of the IPsec policy
      - ipsec_set_policy()
        Generate an IPsec policy specification structure from a readable string
      - ipsec_strerror()
        Error messages for IPsec policy manipulation library
      - IPv6
        Internet Protocol version 6
      - isalnum()
        Test a character to see if it's alphanumeric
      - isalpha()
        Test a character to see if it's alphabetic
      - isascii()
        Test a character to see if it's a 7-bit ASCII character
      - isatty()
        Test to see if a file descriptor is associated with a terminal
      - isblank()
        Test a character to see if it's a blank character
      - iscntrl()
        Test a character to see if it's a control character
      - isdigit()
        Test a character to see if it's a decimal digit
      - isfdtype()
        Test the file type of a file descriptor
      - isfinite()
        Determine if a number is finite
      - isgraph()
        Test a character to see if it's any printable character except a space
      - isgreater()
        Determine whether one floating-point number is greater than another
      - isgreaterequal()
        Determine whether one floating-point number is greater than or equal to another
      - isinf()
        Test for infinity
      - isless()
        Determine whether one floating-point number is less than another
      - islessequal()
        Determine whether one floating-point number is less than or equal to another
      - islessgreater()
        Determine whether one floating-point number is less than or greater than another
      - islower()
        Test a character to see if it's a lowercase letter
      - isnan()
        Test for not-a-number (NaN)
      - isnormal()
        Determine whether a floating-point number is normal
      - isprint()
        Test a character to see if it's any printable character, including a space
      - ispunct()
        Test a character to see if it's any punctuation character
      - isspace()
        Test a character to see if it's a whitespace character
      - isunordered()
        Determine whether two floating-point numbers are unordered
      - isupper()
        Test a character to see if it's an uppercase letter
      - iswalnum()
        Test a wide character to see if it's alphanumeric
      - iswalpha()
        Test a wide character to see if it's alphabetic
      - iswblank()
        Test a wide character to see if it's a blank character
      - iswcntrl()
        Test a wide character to see if it's a control character
      - iswctype()
        Test a wide character to see if it's a given character class
      - iswdigit()
        Test a wide character to see if it's a decimal digit
      - iswgraph()
        Test a wide character to see if it's any printable character except space
      - iswlower()
        Test a wide character to see if it's a lowercase letter
      - iswprint()
        Test a wide character to see if it's any printable character, including space
      - iswpunct()
        Test a wide character to see if it's any punctuation character
      - iswspace()
        Test a wide character to see if it's a whitespace character
      - iswupper()
        Test a character to see if it's an uppercase letter
      - iswxdigit()
        Test a wide character to see if it's a hexadecimal digit
      - isxdigit()
        Test a character to see if it's a hexadecimal digit
      - itoa()
        Convert an integer into a string, using a given base
    - J
    - K
    - L
    - M
    - N
    - O
    - P
    - Q
    - R
    - S
    - T
    - U
    - V
    - W
    - X
    - Y
    - Z
    - Full Safety Information
    - Glossary
  - Devctl and Ioctl Commands
  - JSON Library Reference
  - PAM Reference
  - Utilities Reference
  - WPA Control Interface Reference
    This document provides a reference for the Wi-Fi Protected Access (WPA) control interface, which provides a C API for the WPA/IEEE 802.11i protocols in Wi-Fi client stations. Application developers who want to control WPA operations and get associated status and event data should read this reference.
QNX Hypervisor
The QNX Hypervisor allows you to run multiple OSs on a target system so you can separate critical and non-critical functions, support a wide variety of applications, and reduce hardware costs.
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX software in Amazon Web Services (AWS) and Microsoft Azure (Azure).
QNX Advanced Virtualization Frameworks User's Guide
This User's Guide is aimed at all systems integrators and developers who want to design and build embedded systems using the QNX Advanced Virtualization Frameworks.
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation and explains how to obtain technical support.

inet6_rthdr_segments()

Count the segments in an IPv6 routing header

Synopsis:

#include <netinet/in.h>

int inet6_rthdr_segments(const struct cmsghdr *cmsg);

Arguments:

cmsg: A pointer to ancillary data containing a routing header.

Library:

libsocket

Use the -l socket option to qcc to link against this library.

Description:

This function returns the number of segments (addresses) contained in the routing header described by cmsg.

Based on:

W. Stevens and M. Thomas, Advanced Sockets API for IPv6, RFC 2292, February 1998. Contains good examples.
S. Deering and R. Hinden, Internet Protocol, Version 6 (IPv6) Specification, RFC 2460, December 1998.

Returns:

1 to 23: Success.
-1: An error occurred.

Classification:

RFC 2292


Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

Page updated: March 12, 2026