update for dropped rtnetlink
Kurt Van Dijck
parent
61b18e7ff1
commit
047356608b
15
Readme.md
15
Readme.md
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@ -66,12 +66,20 @@ will use fragementation, emitting 1+ CAN frames.
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# Enable j1939
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CAN has no protocol id field.
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Enabling protocols must be done manually
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Actions need to be performed to enable can-j1939 for a network device
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### on socket connect
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Open a socket and bind to a network interface.
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This is the latest method, and preferred for mainline inclusion
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### netlink
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ip link set can0 j1939 on
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This method is obsoleted in favor of _on socket connect_.
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### procfs for legacy kernel (2.6.25)
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This API is dropped for kernels with netlink support!
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@ -114,6 +122,11 @@ This API is dropped for kernels with netlink support!
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## iproute2
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Older versions of can-j1939 used a modified iproute2
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for manipulating the kernel lists of current addresses.
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This is now obsolete!
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### Static addressing
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ip addr add j1939 0x80 dev can0
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@ -18,14 +18,11 @@ Create a virtual can0 device and start the device
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Use [testj1939](testj1939.c)
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When *can-j1939* is compiled as module, load it.
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When *can-j1939* is compiled as module, opening a socket will load it,
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__or__ you can load it manually
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modprobe can-j1939
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Enable the j1939 protocol stack on the CAN device
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ip link set can0 j1939 on
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Most of the subsequent examples will use 2 sockets programs (in 2 terminals).
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One will use CAN_J1939 sockets using *testj1939*,
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and the other will use CAN_RAW sockets using cansend+candump.
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@ -59,23 +56,12 @@ is not meant for us and *testj1939* does not receive it.
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### Use source address
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Binding a can-j1939 socket to a source address will register
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allow you to send packets.
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./testj1939 can0:0x80
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will say
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./testj1939: bind(): Cannot assign requested address
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Since J1939 maintains addressing, **0x80** has not yet been assigned
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as an address on **can0** . This behaviour is very similar to IP
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addressing: you cannot bind to an address that is not your own.
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Now tell the kernel that we *own* address 0x80.
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It will be available from now on.
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ip addr add j1939 0x80 dev can0
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./testj1939 can0:0x80
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now succeeds.
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Your system had, for a small moment, source address 0x80 assigned.
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### receive with source address
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@ -101,54 +87,30 @@ Open in terminal 1:
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And to these test in another terminal
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./testj1939 -s can0:0x80
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./testj1939 -s can0:0x80,0x3ffff
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This produces **1BFFFF80#0123456789ABCDEF** on CAN.
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./testj1939 -s can0:
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will produce exactly the same because **0x80** is the only
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address currently assigned to **can0:** and is used by default.
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### Multiple source addresses on 1 CAN device
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ip addr add j1939 0x90 dev can0
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./testj1939 -s can0:0x90
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./testj1939 -s can0:0x90,0x3ffff
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produces **1BFFFF90#0123456789ABCDEF** ,
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./testj1939 -s can0:
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### Use PDU1 PGN
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still produces **1BFFFF80#0123456789ABCDEF** , since **0x80**
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is the default _source address_.
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Check
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ip addr show can0
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emits
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X: can0: <NOARP,UP,LOWER_UP> mtu 16 qdisc noqueue state UNKNOWN
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link/can
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can-j1939 0x80 scope link
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can-j1939 0x90 scope link
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0x80 is the first address on can0.
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### Use specific PGN
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./testj1939 -s can0:,0x12345
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./testj1939 -s can0:0x80,0x12345
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emits **1923FF80#0123456789ABCDEF** .
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Note that the real PGN is **0x12300**, and destination address is **0xff**.
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### Emit destination specific packets
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### Use destination address info
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The destination field may be set during sendto().
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*testj1939* implements that like this
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./testj1939 -s can0:,0x12345 can0:0x40
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./testj1939 -s can0:0x80,0x12345 can0:0x40
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emits **19234080#0123456789ABCDEF** .
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@ -167,13 +129,13 @@ __sendto( *peername* )__ , and only one is used.
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For broadcasted transmissions
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./testj1939 -s can0:,0x12300 :,0x32100
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./testj1939 -s can0:0x80,0x12300 :,0x32100
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emits **1B21FF80#0123456789ABCDEF** rather than 1923FF80#012345678ABCDEF
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Desitination specific transmissions
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./testj1939 -s can0:,0x12300 :0x40,0x32100
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./testj1939 -s can0:0x80,0x12300 :0x40,0x32100
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emits **1B214080#0123456789ABCDEF** .
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@ -198,6 +160,14 @@ __50ms__ from each other.
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Destination specific *Transport Protocol* applies flow control
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and may emit CAN packets much faster.
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First assign 0x90 to the local system.
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This becomes important because the kernel must interact in the
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transport protocol sessions before the complete packet is delivered.
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./testj1939 can0:0x90 -r &
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Now test:
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./testj1939 -s20 can0:0x80 :0x90,0x12300
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emits:
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