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dlpi(4p)
dlpi(4P) Network Protocols dlpi(4P)
NAME
dlpi - Data Link Provider Interface
SYNOPSIS
#include <sys/dlpi.h>
DESCRIPTION
Oracle Solaris STREAMS-based device drivers wishing to support the
STREAMS TCP/IP and other STREAMS-based networking protocol suite
implementations support Version 2 of the Data Link Provider Interface
(DLPI). DLPI V2 enables a data link service user to access and use any
of a variety of conforming data link service providers without special
knowledge of the provider's protocol. Specifically, the interface is
intended to support Ethernet, X.25 LAPB, SDLC, ISDN LAPD, CSMA/CD,
FDDI, token ring, token bus, Bisync, and other datalink-level proto‐
cols.
The interface specifies access to the data link service provider in the
form of M_PROTO and M_PCPROTO type STREAMS messages and does not define
a specific protocol implementation. The interface defines the syntax
and semantics of primitives exchanged between the data link user and
the data link provider to attach a physical device with physical-level
address to a stream, bind a datalink-level address to the stream, get
implementation-specific information from the data link provider,
exchange data with a peer data link user in one of three communication
modes (connection, connectionless, acknowledged connectionless),
enable/disable multicast group and promiscuous mode reception of
datalink frames, get and set the physical address associated with a
stream, and several other operations.
Oracle Solaris conforms to The Open Group Technical Standard for Data
Link Provider Interface (DLPI), Version 2. For access to this specifi‐
cation, see https://publications.opengroup.org/c811. Oracle Solaris
also provides extensions to the DLPI standard, as detailed in this man
page.
SOLARIS-SPECIFIC DLPI EXTENSIONS
Notification Support
Enables DLPI consumers to register for notification when events of
interest occur at the DLPI provider. The negotiation can be per‐
formed on any attached DLPI stream, and begins with the DLPI con‐
sumer, sending a DL_NOTIFY_REQ to the provider, which is an M_PROTO
message with the following payload:
typedef struct {
t_uscalar_t dl_primitive;
uint32_t dl_notifications;
uint32_t dl_timelimit;
} dl_notify_req_t;
The dl_primitive field must be set to DL_NOTIFY_REQ; the dl_time‐
limit field is reserved for future use and must be set to zero. The
dl_notifications field is a bitmask containing the event types the
consumer is interested in receiving, and must be zero or more of:
DL_NOTE_LINK_DOWN Notify when link has gone down
DL_NOTE_LINK_UP Notify when link has come up
DL_NOTE_PHYS_DOWN Notify when a link has lost physical
connectivity with the external network
DL_NOTE_PHYS_UP Notify when a link has regained physical
connectivity with the external network
DL_NOTE_PHYS_ADDR Notify when address changes
DL_NOTE_SDU_SIZE Notify when MTU changes
DL_NOTE_SPEED Notify when speed changes
DL_NOTE_PROMISC_ON_PHYS Notify when DL_PROMISC_PHYS is set
DL_NOTE_PROMISC_OFF_PHYS Notify when DL_PROMISC_PHYS is cleared
Consumers might find it useful to send a DL_NOTIFY_REQ message with
no requested types to check if the DLPI provider supports the
extension.
Upon receiving the DL_NOTIFY_REQ, the DLPI provider must generate a
DL_NOTIFY_ACK, which is an M_PROTO message with the following pay‐
load:
typedef struct {
t_uscalar_t dl_primitive;
uint32_t dl_notifications;
} dl_notify_ack_t;
The dl_primitive field must be set to DL_NOTIFY_ACK. The dl_notifi‐
cations field must include any notifications that the provider sup‐
ports, along with any other unrequested notifications that the
provider supports. However, regardless of the notifications the
provider supports, it is restricted to sending only DL_NOTIFY_IND
messages (see below) that were requested in the DL_NOTIFY_REQ.
Since there are additional notification types which are not yet
available for public use, DLPI consumers and providers must take
care when inspecting and setting the dl_notifications field.
Specifically, consumers must be careful to only request the above
notification types, and providers must be careful to not include
any unrecognized notification types in the dl_notifications field
when constructing the DL_NOTIFY_ACK. In addition, DL_NOTIFY_IND's
that are received with undocumented dl_notification or dl_data val‐
ues must be ignored.
DLPI consumers might receive a DL_ERROR_ACK message (with
dl_error_primitive set to DL_NOTIFY_REQ) in response to the initial
DL_NOTIFY_REQ message. This message indicates that the DLPI
provider does not support the DLPI notification extension. Other‐
wise, the DLPI consumer receives a DL_NOTIFY_ACK and should expect
to receive DL_NOTIFY_IND messages for any types that it requested
that were still set in it. The DL_NOTIFY_IND is an M_PROTO message
with the following payload:
typedef struct {
t_uscalar_t dl_primitive;
uint32_t dl_notification;
uint32_t dl_data;
t_uscalar_t dl_addr_length;
t_uscalar_t dl_addr_offset;
} dl_notify_ind_t;
The dl_primitive field must be set to DL_NOTIFY_IND, and the
dl_notification field must be set to the event type that has
occurred (for example, DL_NOTE_LINK_DOWN). Only a single event type
can be set in each DL_NOTIFY_IND.
For the DL_NOTE_SPEED event type, dl_data must be set to the cur‐
rent interface speed in kilobits per second. For the
DL_NOTE_PHYS_ADDR event type, dl_data must be set to
DL_CURR_PHYS_ADDR. For the DL_NOTE_SDU_SIZE event type, dl_data
must be set to the current MTU in bytes. Otherwise, dl_data must be
set to zero.
For the DL_NOTE_PHYS_ADDR event type, the dl_addr_length field must
be set to the length of the address, and the dl_addr_offset field
must be set to offset of the first byte of the address, relative to
b_rptr (for example, if the address immediately follows the
dl_notify_ind structure, dl_addr_offset is set to 'sizeof
(dl_notify_ind)'). For all other event types, the dl_addr_length
and dl_addr_offset fields must be set to zero by DLPI providers and
ignored by DLPI consumers.
In addition to generating DL_NOTIFY_IND messages when a requested
event has occurred, the DLPI provider must initially generate one
or more DL_NOTIFY_IND messages to notify the DLPI consumer of the
current state of the interface. For instance, if the consumer has
requested DL_NOTE_LINK_UP | DL_NOTE_LINK_DOWN, the provider must
send a DL_NOTIFY_IND containing the current state of the link
(either DL_NOTE_LINK_UP or DL_NOTE_LINK_DOWN) after sending the
DL_NOTIFY_ACK.
For the initial DL_NOTIFY_IND message, the DLPI provider is
strongly recommended against sending DL_NOTE_LINK_DOWN, even if the
interface is still initializing and is not yet ready to send or
receive packets. Instead, either delaying the DL_NOTIFY_IND message
until the interface is ready or optimistically reporting
DL_NOTIFY_LINK_UP and subsequently reporting DL_NOTE_LINK_DOWN if
the negotiation fails is strongly preferred. This prevents
DL_NOTIFY_IND consumers from needlessly triggering network failover
operations and logging error messages during network interface ini‐
tialization.
The DLPI provider must continue to generate DL_NOTIFY_IND messages
until it receives a new DL_NOTIFY_REQ message or the DLPI stream is
detached (or closed). Further, a DLPI style 2 provider must keep
track of the requested events after a DL_DETACH_REQ operation, and
if a subsequent DL_ATTACH_REQ is received, it must send gratuitous
DL_NOTIFY_IND messages to notify the consumer of the current state
of the device, since the state might have changed while detached
(or the consumer might have simply discarded its previous state).
Passive Consumers of Aggregated Links
Solaris link aggregations as configured by dladm(8) export DLPI
nodes for both the link aggregation, and individual links that com‐
prises the aggregation, to allow observability of the aggregated
links. To allow applications such as snoop(8) to open those indi‐
vidual aggregated links while disallowing other consumers such as
ip(4P), DL_PASSIVE_REQ (a DLPI primitive), must be issued by
snoop(8) and similar applications.
The DL_PASSIVE_REQ primitive is an M_PROTO message containing the
following payload:
typedef struct {
t_uscalar_t dl_primitive;
} dl_passive_req_t;
Issuing this primitive allows the consumer of a DLPI link to coex‐
ist with a link aggregation that also uses the link. Such a con‐
sumer is considered passive.
Consumers that do not use this primitive while an aggregation is
using the link receive DL_SYSERR/EBUSY when issuing the following
DLPI primitives:
DL_BIND_REQ
DL_ENABMULTI_REQ
DL_PROMISCON_REQ
DL_AGGR_REQ
DL_UNAGGR_REQ
DL_CONTROL_REQ
DL_SET_PHYS_ADDR_REQ
A consumer that has not issued a DL_PASSIVE_REQ and has success‐
fully issued one of the above primitives is considered active.
The creation of a link aggregation using dladm(8) fails if one of
the links included in the aggregation has an active consumer, but
succeeds if the links do not have any DLPI consumers or only pas‐
sive consumers.
Raw Mode
The DLIOCRAW ioctl function is used by some DLPI applications, most
notably the snoop(8) command. The DLIOCRAW command puts the stream
into a raw mode, which, upon receive, causes the full MAC-level
packet to be sent upstream in an M_DATA message instead of it being
transformed into the DL_UNITDATA_IND form normally used for report‐
ing incoming packets. Packet SAP filtering is still performed on
streams that are in raw mode. If a stream user wants to receive all
incoming packets it must also select the appropriate promiscuous
modes. After successfully selecting raw mode, the application is
also allowed to send fully formatted packets to the provider as
M_DATA messages for transmission. DLIOCRAW takes no arguments. Once
enabled, the stream remains in this mode until closed.
Native Mode
Some DLPI providers are able to represent their link layer using
more than one link-layer format. In this case, the default link-
layer format can minimize impact to applications, but might not
allow truly native link-layer headers to be sent or received. DLPI
consumers who wish to use the native link-layer format can use
DLIOCNATIVE to transition the stream. DLIOCNATIVE takes no argu‐
ments and returns the DLPI mac type associated with the new link-
layer format upon success. Once enabled, the stream remains in this
mode until closed. DLIOCNATIVE does not enable transition between
dissimilar DLPI mac types and (aside from the link-layer format),
the new DLPI mac type is guaranteed to be semantically identical.
In particular, the SAP space and addressing format are not affected
and the effect of DLIOCNATIVE is only visible when in raw mode,
though any subsequent DL_INFO_REQ requests generate responses with
dl_mac_type set to the native DLPI type.
Margin
While a DLPI provider provides its maximum SDU using dl_max_sdu in
DL_INFO_ACK messages, this value typically represents a standard
maximum SDU for the provider's media (1500 for Ethernet for exam‐
ple), and not necessarily the absolute maximum amount of data that
the provider is able to transmit in a given data unit. The margin
"is the extra amount of data in bytes that the provider can trans‐
mit beyond its advertised maximum SDU. For example, if a DL_ETHER
provider can handle packets whose payload section is no greater
than 1522 bytes and its dl_max_sdu is set to 1500 (as is typical
for Ethernet), then the margin would be 22. If a provider supports
a non-zero margin, it implements the DLIOCMARGININFO ioctl, whose
data is a t_uscalar_t representing the margin size.
Disabling Loopback
Per the DLPI standard, any message sent on a stream will be looped
back and thus will be received if it matches the specified
dl_level. To prevent this, DL_PROMISC_NOLOOP may be OR'd into the
dl_level field of the dl_promiscon_req_t when issuing a DL_PROMIS‐
CON_REQ. This behavior will remain in effect until promiscuous mode
is disabled by DL_PROMISCOFF_REQ.
DL_ETHER-SPECIFIC DLPI SEMANTICS
VLAN Support
Traditional VLAN Access
Some DL_ETHER DLPI providers support IEEE 802.1Q Virtual LANs (VLAN).
For these providers, traffic for a particular VLAN can be accessed by
opening a VLAN data-link.
Unless raw mode is enabled, a DLPI stream bound to a VLAN data-link
behaves no differently than a traditional DLPI stream. As with non-VLAN
data-link access, data must be sent to a DLPI provider without link-
layer headers (which are added by the provider) and received data is
passed to interested DLPI consumers without link-layer headers. As a
result, DLPI consumers not require special-case logic to implement VLAN
access.
SAP-Based VLAN Access
As per IEEE 802.1Q, all VLAN traffic is sent using EtherType 0x8100,
meaning that in addition to directly opening a VLAN data-link, all VLAN
traffic for a given underline data-link can also be accessed by opening
the underlying data-link and binding to SAP 0x8100. Accordingly, all
VLAN traffic (regardless of VLAN ID) can be sent and received by the
DLPI consumer. However, even when raw mode is disabled, packets are
received starting with their VLAN headers and must be sent to the DLPI
provider with their VLAN headers already pre-pended (but without Ether‐
net headers). Because adhering to these semantics requires each DLPI
consumer to have specialized knowledge of VLANs, VLANs should only be
accessed in this way when the traditional VLAN access method is insuf‐
ficient (for example, because access to all VLAN traffic, regardless of
VLAN ID, is needed).
Because all VLAN traffic is sent with SAP 0x8100, VLAN traffic not fil‐
tered at the physical (DL_PROMISC_PHYS) level is also visible if a DLPI
consumer enables promiscuous mode of a stream at the DL_PROMISC_SAP
level. As mentioned earlier, these packets are received starting with
their VLAN headers if raw mode is not enabled.
QoS Support
The IEEE 802.1Q standard defines eight classes of priority values used
by QoS traffic control of Ethernet packets. Although the priority val‐
ues are encoded in the 802.1Q tags, they can be used independently from
VLANs. In particular, a special priority tagged packet (with VLAN ID
zero but priority bits non-zero) does not belong to any VLAN.
The priority value can be set on either a per-stream or per-packet
basis. DLPI consumers can specify the per-stream priority using the
DL_UDQOS_REQ request (the priority value remains unchanged until the
next DL_UDQOS_REQ) and also specify the per-packet priority value using
the b_band field of a M_DATA message or the dl_priority field of a
DL_UNITDATA_REQ.
Raw Mode
SAP-Based VLAN Access
When raw mode is enabled, the complete, unmodified MAC- level packet
(including Ethernet and VLAN headers) is passed to interested DLPI con‐
sumers. Similarly, the entire MAC-level packet (including Ethernet and
VLAN headers) must be sent to the DLPI provider for transmission. The
priority value specified in the b_band field can be overridden by
encoding the priority value (if any) into the VLAN header.
Traditional VLAN Access
When raw mode is enabled, only packets with the correct VLAN ID are
passed up to interested DLPI consumers. With the exception of priority-
tagged packets, DLPI providers must strip off the VLAN headers (while
retaining the preceding Ethernet headers) before sending up the pack‐
ets. For priority-tagged packets, DLPI providers must use the reserved
tag 0 to encode the VLAN TCI and send up the packets.
On the transmit-side, DLPI consumers must send the packets down to the
DLPI providers without the VLAN headers (but with the Ethernet headers)
unless certain QoS support is required. If QoS support is needed, the
packet can have the VLAN header to indicate the priority value, however
its VLAN ID must be zero. The DLPI providers then insert the VLAN tags
or encode the VLAN tags using the priority value specified in the VLAN
headers and send the packets.
FILES
Files in or under /dev.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.94i) |cw(2.56i) lw(2.94i) |lw(2.56i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ T{ Interface Stability
(Notification support/Passive mode behavior) T}Committed
SEE ALSO
libdlpi(3LIB), gld(4D), ip(4P), dladm(8), snoop(8)
Data Link Provider Interface (DLPI) Standard, Version 2
https://publications.opengroup.org/c811
NOTES
The Solaris DLPI link name can also include a / separated zone name
prefix (for example zonename/linkname). The zone name prefix can be up
to ZONENAME_MAX characters long. The MAXLINKNAMESPECIFIER constant
defines the maximum possible length of a Solaris DLPI link name.
A DLPI link name is at most MAXLINKNAMESPECIFIER characters long. The
zone name prefix of a DLPI link name is at most ZONENAME_MAX characters
long. See dladm(8) for the format and naming restrictions for all
Solaris link names.
Oracle Solaris 11.4 24 Jul 2020 dlpi(4P)