return I2, and inet6_rthdr_getaddr(3) will return I3, The return
value from inet6_rthdr_flags(0) will be f0, inet6_rthdr_flags(1) will
return f1, inet6_rthdr_flags(2) will return f2, and
inet6_rthdr_flags(3) will return f3.
If the receiving application then calls inet6_rthdr_reverse(), the
order of the three addresses will become I3, I2, and I1, and the
order of the four Strict/Loose flags will become f3, f2, f1, and f0.
We can also show what an implementation might store in the ancillary
data object as the Routing header is being built by the sending
process. If we assume a 32-bit architecture where sizeof(struct
cmsghdr) equals 12, with a desired alignment of 4-byte boundaries,
then the call to inet6_rthdr_space(3) returns 68: 12 bytes for the
cmsghdr structure and 56 bytes for the Routing header (8 + 3*16).
The call to inet6_rthdr_init() initializes the ancillary data object
to contain a Type 0 Routing header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=0 | Routing Type=0| Seg Left=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Strict/Loose Bit Map |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The first call to inet6_rthdr_add() adds I1 to the list.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 36 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=2 | Routing Type=0| Seg Left=1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |X| Strict/Loose Bit Map |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] = I1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bit 0 of the Strict/Loose Bit Map contains the value f0, which we
just mark as X. cmsg_len is incremented by 16, the Hdr Ext Len field
is incremented by 2, and the Segments Left field is incremented by 1.
The next call to inet6_rthdr_add() adds I2 to the list.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 52 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=4 | Routing Type=0| Seg Left=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |X|X| Strict/Loose Bit Map |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] = I1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[2] = I2 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The next bit of the Strict/Loose Bit Map contains the value f1.
cmsg_len is incremented by 16, the Hdr Ext Len field is incremented
by 2, and the Segments Left field is incremented by 1.
The last call to inet6_rthdr_add() adds I3 to the list.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 68 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=6 | Routing Type=0| Seg Left=3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |X|X|X| Strict/Loose Bit Map |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] = I1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[2] = I2 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[3] = I3 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The next bit of the Strict/Loose Bit Map contains the value f2.
cmsg_len is incremented by 16, the Hdr Ext Len field is incremented
by 2, and the Segments Left field is incremented by 1.
Finally, the call to inet6_rthdr_lasthop() sets the next bit of the
Strict/Loose Bit Map to the value specified by f3. All the lengths
remain unchanged.
9. Ordering of Ancillary Data and IPv6 Extension Headers
Three IPv6 extension headers can be specified by the application and
returned to the application using ancillary data with sendmsg() and
recvmsg(): Hop-by-Hop options, Destination options, and the Routing
header. When multiple ancillary data objects are transferred via
sendmsg() or recvmsg() and these objects represent any of these three
extension headers, their placement in the control buffer is directly
tied to their location in the corresponding IPv6 datagram. This API
imposes some ordering constraints when using multiple ancillary data
objects with sendmsg().
When multiple IPv6 Hop-by-Hop options having the same option type are
specified, these options will be inserted into the Hop-by-Hop options
header in the same order as they appear in the control buffer. But
when multiple Hop-by-Hop options having different option types are
specified, these options may be reordered by the kernel to reduce
padding in the Hop-by-Hop options header. Hop-by-Hop options may
appear anywhere in the control buffer and will always be collected by
the kernel and placed into a single Hop-by-Hop options header that
immediately follows the IPv6 header.
Similar rules apply to the Destination options: (1) those of the same
type will appear in the same order as they are specified, and (2)
those of differing types may be reordered. But the kernel will build
up to two Destination options headers: one to precede the Routing
header and one to follow the Routing header. If the application
specifies a Routing header then all Destination options that appear
in the control buffer before the Routing header will appear in a
Destination options header before the Routing header and these
options might be reordered, subject to the two rules that we just
stated. Similarly all Destination options that appear in the control
buffer after the Routing header will appear in a Destination options
header after the Routing header, and these options might be
reordered, subject to the two rules that we just stated.
As an example, assume that an application specifies control
information to sendmsg() containing six ancillary data objects: the
first containing two Hop-by-Hop options, the second containing one
Destination option, the third containing two Destination options, the
fourth containing a Routing header, the fifth containing a Hop-by-Hop
option, and the sixth containing two Destination options. We also
assume that all the Hop-by-Hop options are of different types, as are
all the Destination options. We number these options 1-9,
corresponding to their order in the control buffer, and show them on
the left below.
In the middle we show the final arrangement of the options in the
extension headers built by the kernel. On the right we show the four
ancillary data objects returned to the receiving application.
Sender's Receiver's
Ancillary Data --> IPv6 Extension --> Ancillary Data
Objects Headers Objects
------------------ --------------- --------------
HOPOPT-1,2 (first) HOPHDR(J,7,1,2) HOPOPT-7,1,2
DSTOPT-3 DSTHDR(4,5,3) DSTOPT-4,5,3
DSTOPT-4,5 RTHDR(6) RTHDR-6
RTHDR-6 DSTHDR(8,9) DSTOPT-8,9
HOPOPT-7
DSTOPT-8,9 (last)
The sender's two Hop-by-Hop ancillary data objects are reordered, as
are the first two Destination ancillary data objects. We also show a
Jumbo Payload option (denoted as J) inserted by the kernel before the
sender's three Hop-by-Hop options. The first three Destination
options must appear in a Destination header before the Routing
header, and the final two Destination options must appear in a
Destination header after the Routing header.
If Destination options are specified in the control buffer after a
Routing header, or if Destination options are specified without a
Routing header, the kernel will place those Destination options after
an authentication header and/or an encapsulating security payload
header, if present.
10. IPv6-Specific Options with IPv4-Mapped IPv6 Addresses
The various socket options and ancillary data specifications defined
in this document apply only to true IPv6 sockets. It is possible to
create an IPv6 socket that actually sends and receives IPv4 packets,
using IPv4-mapped IPv6 addresses, but the mapping of the options
defined in this document to an IPv4 datagram is beyond the scope of
this document.
In general, attempting to specify an IPv6-only option, such as the
Hop-by-Hop options, Destination options, or Routing header on an IPv6
socket that is using IPv4-mapped IPv6 addresses, will probably result
in an error. Some implementations, however, may provide access to
the packet information (source/destination address, send/receive
interface, and hop limit) on an IPv6 socket that is using IPv4-mapped
IPv6 addresses.
11. rresvport_af
The rresvport() function is used by the rcmd() function, and this
function is in turn called by many of the "r" commands such as
rlogin. While new applications are not being written to use the
rcmd() function, legacy applications such as rlogin will continue to
use it and these will be ported to IPv6.
rresvport() creates an IPv4/TCP socket and binds a "reserved port" to
the socket. Instead of defining an IPv6 version of this function we
define a new function that takes an address family as its argument.
#include <unistd.h>
int rresvport_af(int *port, int family);
This function behaves the same as the existing rresvport() function,
but instead of creating an IPv4/TCP socket, it can also create an
IPv6/TCP socket. The family argument is either AF_INET or AF_INET6,
and a new error return is EAFNOSUPPORT if the address family is not
supported.
(Note: There is little consensus on which header defines the
rresvport() and rcmd() function prototypes. 4.4BSD defines it in
<unistd.h>, others in <netdb.h>, and others don't define the function
prototypes at all.)
(Note: We define this function only, and do not define something like
rcmd_af() or rcmd6(). The reason is that rcmd() calls
gethostbyname(), which returns the type of address: AF_INET or
AF_INET6. It should therefore be possible to modify rcmd() to
support either IPv4 or IPv6, based on the address family returned by
gethostbyname().)
12. Future Items
Some additional items may require standardization, but no concrete
proposals have been made for the API to perform these tasks. These
may be addressed in a later document.
12.1. Flow Labels
Earlier revisions of this document specified a set of
inet6_flow_XXX() functions to assign, share, and free IPv6 flow
labels. Consensus, however, indicated that it was premature to
specify this part of the API.
12.2. Path MTU Discovery and UDP
A standard method may be desirable for a UDP application to determine
the "maximum send transport-message size" (Section 5.1 of [RFC-1981])
to a given destination. This would let the UDP application send
smaller datagrams to the destination, avoiding fragmentation.
12.3. Neighbor Reachability and UDP
A standard method may be desirable for a UDP application to tell the
kernel that it is making forward progress with a given peer (Section
7.3.1 of [RFC-1970]). This could save unneeded neighbor
solicitations and neighbor advertisements.
13. Summary of New Definitions
The following list summarizes the constants and structure,
definitions discussed in this memo, sorted by header.
<netinet/icmp6.h> ICMP6_DST_UNREACH
<netinet/icmp6.h> ICMP6_DST_UNREACH_ADDR
<netinet/icmp6.h> ICMP6_DST_UNREACH_ADMIN
<netinet/icmp6.h> ICMP6_DST_UNREACH_NOPORT
<netinet/icmp6.h> ICMP6_DST_UNREACH_NOROUTE
<netinet/icmp6.h> ICMP6_DST_UNREACH_NOTNEIGHBOR
<netinet/icmp6.h> ICMP6_ECHO_REPLY
<netinet/icmp6.h> ICMP6_ECHO_REQUEST
<netinet/icmp6.h> ICMP6_INFOMSG_MASK
<netinet/icmp6.h> ICMP6_MEMBERSHIP_QUERY
<netinet/icmp6.h> ICMP6_MEMBERSHIP_REDUCTION
<netinet/icmp6.h> ICMP6_MEMBERSHIP_REPORT
<netinet/icmp6.h> ICMP6_PACKET_TOO_BIG
<netinet/icmp6.h> ICMP6_PARAMPROB_HEADER
<netinet/icmp6.h> ICMP6_PARAMPROB_NEXTHEADER
<netinet/icmp6.h> ICMP6_PARAMPROB_OPTION
<netinet/icmp6.h> ICMP6_PARAM_PROB
<netinet/icmp6.h> ICMP6_TIME_EXCEEDED
<netinet/icmp6.h> ICMP6_TIME_EXCEED_REASSEMBLY
<netinet/icmp6.h> ICMP6_TIME_EXCEED_TRANSIT
<netinet/icmp6.h> ND_NA_FLAG_OVERRIDE
<netinet/icmp6.h> ND_NA_FLAG_ROUTER
<netinet/icmp6.h> ND_NA_FLAG_SOLICITED
<netinet/icmp6.h> ND_NEIGHBOR_ADVERT
<netinet/icmp6.h> ND_NEIGHBOR_SOLICIT
<netinet/icmp6.h> ND_OPT_MTU
<netinet/icmp6.h> ND_OPT_PI_FLAG_AUTO
<netinet/icmp6.h> ND_OPT_PI_FLAG_ONLINK
<netinet/icmp6.h> ND_OPT_PREFIX_INFORMATION
<netinet/icmp6.h> ND_OPT_REDIRECTED_HEADER
<netinet/icmp6.h> ND_OPT_SOURCE_LINKADDR
<netinet/icmp6.h> ND_OPT_TARGET_LINKADDR
<netinet/icmp6.h> ND_RA_FLAG_MANAGED
<netinet/icmp6.h> ND_RA_FLAG_OTHER
<netinet/icmp6.h> ND_REDIRECT
<netinet/icmp6.h> ND_ROUTER_ADVERT
<netinet/icmp6.h> ND_ROUTER_SOLICIT
<netinet/icmp6.h> struct icmp6_filter{};
<netinet/icmp6.h> struct icmp6_hdr{};
<netinet/icmp6.h> struct nd_neighbor_advert{};
<netinet/icmp6.h> struct nd_neighbor_solicit{};
<netinet/icmp6.h> struct nd_opt_hdr{};
<netinet/icmp6.h> struct nd_opt_mtu{};
<netinet/icmp6.h> struct nd_opt_prefix_info{};
<netinet/icmp6.h> struct nd_opt_rd_hdr{};
<netinet/icmp6.h> struct nd_redirect{};
<netinet/icmp6.h> struct nd_router_advert{};
<netinet/icmp6.h> struct nd_router_solicit{};
<netinet/in.h> IPPROTO_AH
<netinet/in.h> IPPROTO_DSTOPTS
<netinet/in.h> IPPROTO_ESP
<netinet/in.h> IPPROTO_FRAGMENT
<netinet/in.h> IPPROTO_HOPOPTS
<netinet/in.h> IPPROTO_ICMPV6
<netinet/in.h> IPPROTO_IPV6
<netinet/in.h> IPPROTO_NONE
<netinet/in.h> IPPROTO_ROUTING
<netinet/in.h> IPV6_DSTOPTS
<netinet/in.h> IPV6_HOPLIMIT
<netinet/in.h> IPV6_HOPOPTS
<netinet/in.h> IPV6_NEXTHOP
<netinet/in.h> IPV6_PKTINFO
<netinet/in.h> IPV6_PKTOPTIONS
<netinet/in.h> IPV6_RTHDR
<netinet/in.h> IPV6_RTHDR_LOOSE
<netinet/in.h> IPV6_RTHDR_STRICT
<netinet/in.h> IPV6_RTHDR_TYPE_0
<netinet/in.h> struct in6_pktinfo{};
<netinet/ip6.h> IP6F_OFF_MASK
<netinet/ip6.h> IP6F_RESERVED_MASK
<netinet/ip6.h> IP6F_MORE_FRAG
<netinet/ip6.h> struct ip6_dest{};
<netinet/ip6.h> struct ip6_frag{};
<netinet/ip6.h> struct ip6_hbh{};
<netinet/ip6.h> struct ip6_hdr{};
<netinet/ip6.h> struct ip6_rthdr{};
<netinet/ip6.h> struct ip6_rthdr0{};
<sys/socket.h> struct cmsghdr{};
<sys/socket.h> struct msghdr{};
The following list summarizes the function and macro prototypes
discussed in this memo, sorted by header.
<netinet/icmp6.h> void ICMP6_FILTER_SETBLOCK(int,
struct icmp6_filter *);
<netinet/icmp6.h> void ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *);
<netinet/icmp6.h> void ICMP6_FILTER_SETPASS(int, struct icmp6_filter *);
<netinet/icmp6.h> void ICMP6_FILTER_SETPASSALL(struct icmp6_filter *);
<netinet/icmp6.h> int ICMP6_FILTER_WILLBLOCK(int,
const struct icmp6_filter *);
<netinet/icmp6.h> int ICMP6_FILTER_WILLPASS(int,
const struct icmp6_filter *);
<netinet/in.h> int IN6_ARE_ADDR_EQUAL(const struct in6_addr *,
const struct in6_addr *);
<netinet/in.h> uint8_t *inet6_option_alloc(struct cmsghdr *,
int, int, int);
<netinet/in.h> int inet6_option_append(struct cmsghdr *,
const uint8_t *, int, int);
<netinet/in.h> int inet6_option_find(const struct cmsghdr *,
uint8_t *, int);
<netinet/in.h> int inet6_option_init(void *, struct cmsghdr **, int);
<netinet/in.h> int inet6_option_next(const struct cmsghdr *,
uint8_t **);
<netinet/in.h> int inet6_option_space(int);
<netinet/in.h> int inet6_rthdr_add(struct cmsghdr *,
const struct in6_addr *,
unsigned int);
<netinet/in.h> struct in6_addr inet6_rthdr_getaddr(struct cmsghdr *,
int);
<netinet/in.h> int inet6_rthdr_getflags(const struct cmsghdr *, int);
<netinet/in.h> struct cmsghdr *inet6_rthdr_init(void *, int);
<netinet/in.h> int inet6_rthdr_lasthop(struct cmsghdr *,
unsigned int);
<netinet/in.h> int inet6_rthdr_reverse(const struct cmsghdr *,
struct cmsghdr *);
<netinet/in.h> int inet6_rthdr_segments(const struct cmsghdr *);
<netinet/in.h> size_t inet6_rthdr_space(int, int);
<sys/socket.h> unsigned char *CMSG_DATA(const struct cmsghdr *);
<sys/socket.h> struct cmsghdr *CMSG_FIRSTHDR(const struct msghdr *);
<sys/socket.h> unsigned int CMSG_LEN(unsigned int);
<sys/socket.h> struct cmsghdr *CMSG_NXTHDR(const struct msghdr *mhdr,
const struct cmsghdr *);
<sys/socket.h> unsigned int CMSG_SPACE(unsigned int);
<unistd.h> int rresvport_af(int *, int);
14. Security Considerations
The setting of certain Hop-by-Hop options and Destination options may
be restricted to privileged processes. Similarly some Hop-by-Hop
options and Destination options may not be returned to nonprivileged
applications.
15. Change History
Changes from the June 1997 Edition (-03 draft)
- Added a note that defined constants for multibyte fields are in
network byte order. This affects the ip6f_offlg member of the
Fragment header (Section 2.1.2) and the nd_na_flags_reserved
member of the nd_neighbor_advert structure (Section 2.2.2).
- Section 5: the ipi6_ifindex member of the in6_pktinfo structure
should be "unsigned int" instead of "int", for consistency with
the interface indexes in [RFC-2133].
- Section 6.3.7: the three calls to inet6_option_space() in the
examples needed to be arguments to malloc(). The final one of
these was missing the "6" in the name "inet6_option_space".
- Section 8.6: the function prototype for inet6_rthdr_segments()
was missing the ending semicolon.
Changes from the March 1997 Edition (-02 draft)
- In May 1997 Draft 6.6 of Posix 1003.1g (called Posix.1g herein)
passed ballot and will be forwarded to the IEEE Standards Board
later in 1997 for final approval. Some changes made for this
final Posix draft are incorporated into this Internet Draft,
specifically the datatypes mentioned in Section 1 (and used
throughout the text), and the socklen_t datatype used in Section
4.1 and 4.2.
- Section 1: Added the intN_t signed datatypes, changed the
datatype u_intN_t to uintN_t (no underscore after the "u"), and
removed the datatype u_intNm_t, as per Draft 6.6 of Posix.1g.
- Name space issues for structure and constant names in Section 2:
Many of the structure member names and constant names were
changed so that the prefixes are the same. The following
prefixes are used for structure members: "ip6_", "icmp6_", and
"nd_". All constants have the prefixes "ICMP6_" and "ND_".
- New definitions: Section 2.1.2: contains definitions for the IPv6
extension headers, other than AH and ESP. Section 2.2.2:
contains additional structures and constants for the neighbor
discovery option header and redirected header.
- Section 2.2.2: the enum for the neighbor discovery option field
was changed to be a set of #define constants.
- Changed the word "function" to "macro" for references to all the
uppercase names in Sections 2.3 (IN6_ARE_ADDR_EQUAL), 3.2
(ICMPV6_FILTER_xxx), and 4.3 (CMSG_xxx).
- Added more protocols to the /etc/protocols file (Section 2.4) and
changed the name of "icmpv6" to "ipv6-icmp".
- Section 3: Made it more explicit that an application cannot read
or write entire IPv6 packets, that all extension headers are
passed as ancillary data. Added a sentence that the kernel
fragments packets written to an IPv6 raw socket when necessary.
Added a note that IPPROTO_RAW raw IPv6 sockets are not special.
- Section 3.1: Explicitly stated that the checksum option applies
to both outgoing packets and received packets.
- Section 3.2: Changed the array name within the icmp6_filter
structure from "data" to "icmp6_filt". Changes the prefix for
the filter macros from "ICMPV6_" to "ICMP6_", for consistency
with the names in Section 2.2. Changed the example from a ping
program to a program that wants to receive only router
advertisements.
- Section 4.1: Changed msg_namelen and msg_controllen from size_t
to the Posix.1g socklen_t datatype. Updated the Note that
follows.
- Section 4.2: Changed cmsg_len from size_t to the Posix.1g
socklen_t datatype. Updated the Note that follows.
- Section 4.4: Added a Note that the second and third arguments to
getsockopt() and setsockopt() are intentionally the same as the
cmsg_level and cmsg_type members.
- Section 4.5: Reorganized the section into a description of the
option, followed by the TCP semantics, and the UDP and raw socket
semantics. Added a sentence on how to clear all the sticky
options. Added a note that TCP need not save the options from
the most recently received segment until the application says to
do so. Added the statement that ancillary data is never passed
with sendmsg() or recvmsg() on a TCP socket. Simplified the
interaction of the sticky options with ancillary data for UDP or
raw IP: none of the sticky options are sent if ancillary data is
specified.
- Final paragraph of Section 5.1: ipi6_index should be
ipi6_ifindex.
- Section 5.4: Added a note on the term "privileged".
- Section 5.5: Noted that the errors listed are examples, and the
actual errors depend on the implementation.
- Removed Section 6 ("Flow Labels") as the consensus is that it is
premature to try and specify an API for this feature. Access to
the flow label field in the IPv6 header is still provided through
the sin6_flowinfo member of the IPv6 socket address structure in
[RFC-2133]. Added a subsection to Section 13 that this is a
future item.
All remaining changes are identified by their section number in
the previous draft. With the removal of Section 6, the section
numbers are decremented by one.
- Section 7.3.7: the calls to malloc() in all three examples should
be calls to inet6_option_space() instead. The two calls to
inet6_option_append() in the third example should be calls to
inet6_option_alloc(). The two calls to CMSG_SPACE() in the first
and third examples should be calls to CMSG_LEN(). The second
call to CMSG_SPACE() in the second example should be a call to
CMSG_LEN().
- Section 7.3.7: All the opt_X_ and opt_Y_ structure member names
were changed to be ip6_X_opt_ and ip6_Y_opt_. The two structure
names ipv6_opt_X and ipv6_opt_Y were changed to ip6_X_opt and
ip6_Y_opt. The constants beginning with IPV6_OPT_X_ and
IPV6_OPT_Y_ were changed to begin with IP6_X_OPT_ and IP6_Y_OPT_.
- Use the term "Routing header" throughout the draft, instead of
"source routing". Changed the names of the eight
inet6_srcrt_XXX() functions in Section 9 to inet6_rthdr_XXX().
Changed the name of the socket option from IPV6_SRCRT to
IPV6_RTHDR, and the names of the three IPV6_SRCRT_xxx constants
in Section 9 to IPV6_RTHDR_xxx.
- Added a paragraph to Section 9 on how to receive and send a
Routing header.
- Changed inet6_rthdr_add() and inet6_rthdr_reverse() so that they
return -1 upon an error, instead of an Exxx errno value.
- In the description of inet6_rthdr_space() in Section 9.1, added
the qualifier "For an IPv6 Type 0 Routing header" to the
restriction of between 1 and 23 segments.
- Refer to final function argument in Sections 9.7 and 9.8 as
index, not offset.
- Updated Section 14 with new names from Section 2.
- Changed the References from "[n]" to "[RFC-abcd]".
Changes from the February 1997 Edition (-01 draft)
- Changed the name of the ip6hdr structure to ip6_hdr (Section 2.1)
for consistency with the icmp6hdr structure. Also changed the
name of the ip6hdrctl structure contained within the ip6_hdr
structure to ip6_hdrctl (Section 2.1). Finally, changed the name
of the icmp6hdr structure to icmp6_hdr (Section 2.2). All other
occurrences of this structure name, within the Neighbor Discovery
structures in Section 2.2.1, already contained the underscore.
- The "struct nd_router_solicit" and "struct nd_router_advert"
should both begin with "nd6_". (Section 2.2.2).
- Changed the name of in6_are_addr_equal to IN6_ARE_ADDR_EQUAL
(Section 2.3) for consistency with basic API address testing
functions. The header defining this macro is <netinet/in.h>.
- getprotobyname("ipv6") now returns 41, not 0 (Section 2.4).
- The first occurrence of "struct icmpv6_filter" in Section 3.2
should be "struct icmp6_filter".
- Changed the name of the CMSG_LENGTH() macro to CMSG_LEN()
(Section 4.3.5), since LEN is used throughout the <netinet/*.h>
headers.
- Corrected the argument name for the sample implementations of the
CMSG_SPACE() and CMSG_LEN() macros to be "length" (Sections 4.3.4
and 4.3.5).
- Corrected the socket option mentioned in Section 5.1 to specify
the interface for multicasting from IPV6_ADD_MEMBERSHIP to
IPV6_MULTICAST_IF.
- There were numerous errors in the previous draft that specified
<netinet/ip6.h> that should have been <netinet/in.h>. These have
all been corrected and the locations of all definitions is now
summarized in the new Section 14 ("Summary of New Definitions").
Changes from the October 1996 Edition (-00 draft)
- Numerous rationale added using the format (Note: ...).
- Added note that not all errors may be defined.
- Added note about ICMPv4, IGMPv4, and ARPv4 terminology.
- Changed the name of <netinet/ip6_icmp.h> to <netinet/icmp6.h>.
- Changed some names in Section 2.2.1: ICMPV6_PKT_TOOBIG to
ICMPV6_PACKET_TOOBIG, ICMPV6_TIME_EXCEED to ICMPV6_TIME_EXCEEDED,
ICMPV6_ECHORQST to ICMPV6_ECHOREQUEST, ICMPV6_ECHORPLY to
ICMPV6_ECHOREPLY, ICMPV6_PARAMPROB_HDR to
ICMPV6_PARAMPROB_HEADER, ICMPV6_PARAMPROB_NXT_HDR to
ICMPV6_PARAMPROB_NEXTHEADER, and ICMPV6_PARAMPROB_OPTS to
ICMPV6_PARAMPROB_OPTION.
- Prepend the prefix "icmp6_" to the three members of the
icmp6_dataun union of the icmp6hdr structure (Section 2.2).
- Moved the neighbor discovery definitions into the
<netinet/icmp6.h> header, instead of being in their own header
(Section 2.2.1).
- Changed Section 2.3 ("Address Testing"). The basic macros are
now in the basic API.
- Added the new Section 2.4 on "Protocols File".
- Added note to raw sockets description that something like BPF or
DLPI must be used to read or write entire IPv6 packets.
- Corrected example of IPV6_CHECKSUM socket option (Section 3.1).
Also defined value of -1 to disable.
- Noted that <netinet/icmp6.h> defines all the ICMPv6 filtering
constants, macros, and structures (Section 3.2).
- Added note on magic number 10240 for amount of ancillary data
(Section 4.1).
- Added possible padding to picture of ancillary data (Section
4.2).
- Defined <sys/socket.h> header for CMSG_xxx() functions (Section
4.2).
- Note that the data returned by getsockopt(IPV6_PKTOPTIONS) for a
TCP socket is just from the optional headers, if present, of the
most recently received segment. Also note that control
information is never returned by recvmsg() for a TCP socket.
- Changed header for struct in6_pktinfo from <netinet.in.h> to
<netinet/ip6.h> (Section 5).
- Removed the old Sections 5.1 and 5.2, because the interface
identification functions went into the basic API.
- Redid Section 5 to support the hop limit field.
- New Section 5.4 ("Next Hop Address").
- New Section 6 ("Flow Labels").
- Changed all of Sections 7 and 8 dealing with Hop-by-Hop and
Destination options. We now define a set of inet6_option_XXX()
functions.
- Changed header for IPV6_SRCRT_xxx constants from <netinet.in.h>
to <netinet/ip6.h> (Section 9).
- Add inet6_rthdr_lasthop() function, and fix errors in description
of Routing header (Section 9).
- Reworded some of the Routing header descriptions to conform to
the terminology in [RFC-1883].
- Added the example from [RFC-1883] for the Routing header (Section
9.9).
- Expanded the example in Section 10 to show multiple options per
ancillary data object, and to show the receiver's ancillary data
objects.
- New Section 11 ("IPv6-Specific Options with IPv4-Mapped IPv6
Addresses").
- New Section 12 ("rresvport_af").
- Redid old Section 10 ("Additional Items") into new Section 13
("Future Items").
16. References
[RFC-1883] Deering, S., and R. Hinden, "Internet Protocol, Version 6
(IPv6), Specification", RFC1883, December 1995.
[RFC-2133] Gilligan, R., Thomson, S., Bound, J., and W. Stevens,
"Basic Socket Interface Extensions for IPv6", RFC2133,
April 1997.
[RFC-1981] McCann, J., Deering, S., and J. Mogul, "Path MTU
Discovery
for IP version 6", RFC1981, August 1996.
[RFC-1970] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC1970, August
1996.
17. Acknowledgments
Matt Thomas and Jim Bound have been working on the technical details
in this draft for over a year. Keith Sklower is the original
implementor of ancillary data in the BSD networking code. Craig Metz
provided lots of feedback, suggestions, and comments based on his
implementing many of these features as the document was being
written.
The following provided comments on earlier drafts: Pascal Anelli,
Hamid Asayesh, Ran Atkinson, Karl Auerbach, Hamid Asayesh, Matt
Crawford, Sam T. Denton, Richard Draves, Francis Dupont, Bob
Gilligan, Tim Hartrick, Masaki Hirabaru, Yoshinobu Inoue, Mukesh
Kacker, A. N. Kuznetsov, Pedro Marques, Jack McCann, der Mouse, John
Moy, Thomas Narten, Erik Nordmark, Steve Parker, Charles Perkins, Tom
Pusateri, Pedro Roque, Sameer Shah, Peter Sjodin, Stephen P.
Spackman, Jinmei Tatuya, Karen Tracey, Quaizar Vohra, Carl Williams,
Steve Wise, and Kazu Yamamoto.
18. Authors' Addresses
W. Richard Stevens
1202 E. Paseo del Zorro
Tucson, AZ 85718
EMail: rstevens@kohala.com
Matt Thomas
AltaVista Internet Software
LJO2-1/J8
30 Porter Rd
Littleton, MA 01460
EMail: matt.thomas@altavista-software.com
19. Full Copyright Statement
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