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35 .Nd Kernel network dispatch service
39 .Fn netisr_register "const struct netisr_handler *nhp"
41 .Fn netisr_unregister "const struct netisr_handler *nhp"
43 .Fn netisr_dispatch "u_int proto" "struct mbuf *m"
45 .Fn netisr_dispatch_src "u_int proto" "uintptr_t source" "struct mbuf *m"
47 .Fn netisr_queue "u_int proto" "struct mbuf *m"
49 .Fn netisr_queue_src "u_int proto" "uintptr_t source" "struct mbuf *m"
51 .Fn netisr_clearqdrops "const struct netisr_handler *nhp"
53 .Fn netisr_getqdrops "const struct netisr_handler *nhp" "u_int64_t *qdropsp"
55 .Fn netisr_getqlimit "const struct netisr_handler *nhp" "u_int *qlimitp"
57 .Fn netisr_setqlimit "const struct netisr_handler *nhp" "u_int qlimit"
59 .Fn netisr_default_flow2cpu "u_int flowid"
61 .Fn netisr_get_cpucount "void"
63 .Fn netisr_get_cpuid "u_int cpunumber"
67 kernel interface suite allows device drivers (and other packet sources) to
68 direct packets to protocols for directly dispatched or deferred processing.
69 .Ss Protocol registration
70 Protocols register and unregister handlers using
73 .Fn netisr_unregister ,
74 and may also manage queue limits and statistics using the
75 .Fn netisr_clearqdrops ,
76 .Fn netisr_getqdrops ,
77 .Fn netisr_getqlimit ,
82 supports multi-processor execution of handlers, and relies on a combination
83 of source ordering and protocol-specific ordering and work-placement
84 policies to decide how do distribute work across one or more worker
86 Registering protocols will declare one of three policies:
87 .Bl -tag -width NETISR_POLICY_SOURCE
88 .It Dv NETISR_POLICY_SOURCE
90 should maintain source ordering without advice from the protocol.
92 will ignore any flow IDs present on
94 headers for the purposes of work placement.
95 .It Dv NETISR_POLICY_FLOW
97 should maintain flow ordering as defined by the
100 If the protocol implements
104 will query the protocol in the evet that the
106 doesn't have a flow ID, falling back on source ordering.
107 .It NETISR_POLICY_CPU
109 will entirely delegate all work placement decisions to the protocol,
115 Registration is declared using
116 .Vt "struct netisr_handler" ,
117 whose fields are defined as follows:
118 .Bl -tag -width "netisr_handler_t nh_handler"
119 .It Vt "const char *" Va nh_name
120 Unique character string name of the protocol, which may be included in
122 MIB names, so should not contain whitespace.
123 .It Vt netisr_handler_t Va nh_handler
124 Protocol handler function that will be invoked on each packet received for
126 .It Vt netisr_m2flow_t Va nh_m2flow
127 Optional protocol function to generate a flow ID and set
129 for packets that do not enter
134 Will be used only with
135 .Dv NETISR_POLICY_FLOW .
136 .It Vt netisr_m2cpuid_t Va nh_m2cpuid
137 Protocol function to determine what CPU a packet should be processed on.
138 Will be used only with
139 .Dv NETISR_POLICY_CPU .
140 .It Vt netisr_drainedcpu_t Va nh_drainedcpu
141 Optional callback function that will be invoked when a per-CPU queue
143 It will never fire for directly dispatched packets.
144 Unless fully understood, this special-purpose function should not be used.
145 .\" In case you intend to use this please send 50 chocolate bars to each
146 .\" of rwatson and bz and wait for an answer.
147 .It Vt u_int Va nh_proto
148 Protocol number used by both protocols to identify themselves to
150 and by packet sources to select what handler will be used to process
152 A table of supported protocol numbers appears below.
153 For implementation reasons, protocol numbers great than 15 are currently
155 .It Vt u_int Va nh_qlimit
156 The maximum per-CPU queue depth for the protocol; due to internal
157 implementation details, the effective queue depth may be as much as twice
159 .It Vt u_int Va nh_policy
160 The ordering and work placement policy for the protocol, as described
163 .Ss Packet source interface
164 Packet sources, such as network interfaces, may request protocol processing
170 Both accept a protocol number and
174 will always execute the protocol handler asynchonously in a deferred
177 will optionally direct dispatch if permitted by global and per-protocol
180 In order to provide additional load balancing and flow information,
181 packet sources may also specify an opaque source identifier, which in
182 practice might be a network interface number or socket pointer, using
184 .Fn netisr_dispatch_src
188 .Ss Protocol number constants
189 The follow protocol numbers are currently defined:
190 .Bl -tag -width NETISR_ATALK1
196 Routing socket loopback
215 This manual page and the
217 implementation were written by
218 .An Robert N. M. Watson .