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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"
56 .Fn netisr_getqlimit "const struct netisr_handler *nhp" "u_int *qlimitp"
58 .Fn netisr_setqlimit "const struct netisr_handler *nhp" "u_int qlimit"
60 .Fn netisr_default_flow2cpu "u_int flowid"
62 .Fn netisr_get_cpucount "void"
64 .Fn netisr_get_cpuid "u_int cpunumber"
68 kernel interface suite allows device drivers (and other packet sources) to
69 direct packets to protocols for directly dispatched or deferred processing.
70 .Ss Protocol registration
71 Protocols register and unregister handlers using
74 .Fn netisr_unregister ,
75 and may also manage queue limits and statistics using the
76 .Fn netisr_clearqdrops ,
77 .Fn netisr_getqdrops ,
78 .Fn netisr_getqlimit ,
83 supports multi-processor execution of handlers, and relies on a combination
84 of source ordering and protocol-specific ordering and work-placement
85 policies to decide how do distribute work across one or more worker
87 Registering protocols will declare one of three policies:
88 .Bl -tag -width NETISR_POLICY_SOURCE
89 .It Dv NETISR_POLICY_SOURCE
91 should maintain source ordering without advice from the protocol.
93 will ignore any flow IDs present on
95 headers for the purposes of work placement.
96 .It Dv NETISR_POLICY_FLOW
98 should maintain flow ordering as defined by the
100 header flow ID field.
101 If the protocol implements
105 will query the protocol in the evet that the
107 doesn't have a flow ID, falling back on source ordering.
108 .It NETISR_POLICY_CPU
110 will entirely delegate all work placement decisions to the protocol,
116 Registration is declared using
117 .Vt "struct netisr_handler" ,
118 whose fields are defined as follows:
119 .Bl -tag -width "netisr_handler_t nh_handler"
120 .It Vt "const char *" Va nh_name
121 Unique character string name of the protocol, which may be included in
123 MIB names, so should not contain whitespace.
124 .It Vt netisr_handler_t Va nh_handler
125 Protocol handler function that will be invoked on each packet received for
127 .It Vt netisr_m2flow_t Va nh_m2flow
128 Optional protocol function to generate a flow ID and set
130 for packets that do not enter
135 Will be used only with
136 .Dv NETISR_POLICY_FLOW .
137 .It Vt netisr_m2cpuid_t Va nh_m2cpuid
138 Protocol function to determine what CPU a packet should be processed on.
139 Will be used only with
140 .Dv NETISR_POLICY_CPU .
141 .It Vt u_int Va nh_proto
142 Protocol number used by both protocols to identify themselves to
144 and by packet sources to select what handler will be used to process
146 A table of supported protocol numbers appears below.
147 For implementation reasons, protocol numbers great than 15 are currently
149 .It Vt u_int Va nh_qlimit
150 The maximum per-CPU queue depth for the protocol; due to internal
151 implementation details, the effective queue depth may be as much as twice
153 .It Vt u_int Va nh_policy
154 The ordering and work placement policy for the protocol, as described
157 .Ss Packet source interface
158 Packet sources, such as network interfaces, may request protocol processing
164 Both accept a protocol number and
168 will always execute the protocol handler asynchonously in a deferred
171 will optionally direct dispatch if permitted by global and per-protocol
174 In order to provide additional load balancing and flow information,
175 packet sources may also specify an opaque source identifier, which in
176 practice might be a network interface number or socket pointer, using
178 .Fn netisr_dispatch_src
182 .Ss Protocol number constants
183 The follow protocol numbers are currently defined:
184 .Bl -tag -width NETISR_ATALK1
190 Routing socket loopback
207 This manual page and the
209 implementation were written by
210 .An Robert N. M. Watson .