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freebsd/sys/netgraph/NOTES
Julian Elischer 069154d55f Rewrite of netgraph to start getting ready for SMP.
This version is functional and is aproaching solid..
notice I said APROACHING. There are many node types I cannot test
I have tested: echo hole ppp socket vjc iface tee bpf async tty
The rest compile and "Look" right.  More changes to follow.
DEBUGGING is enabled in this code to help if people have problems.
2001-01-06 00:46:47 +00:00

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$FreeBSD$
Development ideas..
Archie's suggestions... :-)
- There should be a new malloc type: M_NETGRAPH
[DONE]
- all mallocs/frees now changed to use this.. JRE
- might further split them out some time.
- Use MALLOC and FREE macros instead of direct function calls
[DONE]
- They allow conditional compilation which keeps
statistics & counters on various memory allocation
(or so it seems)
- Now tend to have NG_FREE_XX() macros. they
allow better debugging
- In struct ng_mesg: at least make "header" into "hdr", if not
getting rid of it altogether. It doesn't seem necessary and
makes all my C code lines too long.
- I understand.. one thought however.. consider..
if char data[0] were not legal, so that data[1] needed to be
used instead, then the only way to get the size of the header
would be sizeof(msg.header) as sizeof(msg) would include the dummy
following bytes. this is a portability issue and I hope
it will be ported eventually :)
- Baloney! you can use sizeof(msg) - 1 then.. or just
make it a macro, then its always portable:
#ifdef __GNU_C__
#define NG_MSG_HDR_SIZE (sizeof(struct ng_message))
#else
#define NG_MSG_HDR_SIZE (sizeof(struct ng_message) - 1)
#endif
- inertia rules :-b
- Have a user level program to print out and manipulate nodes, etc.
- [DONE]
see ngctl, nghook
- "Netgraph global" flags to turn on tracing, etc.
- ngctl needs to be rewritten using libnetgraph. Also it needs a
command to list all existing nodes (in case you don't know the
name of what you're looking for).
[DONE]
- Need a way to get a list of ALL nodes.
[DONE]
- see NGM_LISTNODES
- Enhance "netstat" to display all netgraph nodes -- or at least
all netgraph socket nodes.
[DONE]
- BUG FIX: bind() on a socket should neither require nor allow a
colon character at the end of the name. Note ngctl allows you
to do it either way!
[DONE] (I think)
- bind on a control socket has been disabled
it was a bad idea.
- Need to implement passing meta information through socket nodes
using sendmsg() and recvmsg().
- Stuff needing to be added to manual:
- Awareness of SPL level, use ng_queue*() functions when necessary.
- Malloc all memory with type M_NETGRAPH. -DONE
- Write code so it can be an LKM or built into the kernel.. this means
be careful with things like #ifdef INET.
- All nodes assume that all data mbufs have the M_PKTHDR flag set!
The ng_send_data() and related functions should have an
#ifdef DIAGNOSTICS check to check this assumption for every mbuf.
-DONE with INVARIANTS. Framework should test this more.
- More generally, netgraph code should make liberal use of the
#ifdef DIAGNOSTICS definition.
-INVARIANTS.
- Since data and messages are sent functionally, programmers need
to watch out for infinite feedback loops. Should ng_base.c detect
this automatically?
- I've been thinking about this. each node could have a 'colour'
which is set to the colour of the packet as you pass through.
hitting a node already of your colour would abort. Each packet
has another (incremented) colour.
-new 'item' type can hold a hopcount...
NEW in 2001
All piggyback responses have gone away.
use the node ID in the return address field for quick response delivery.
Every node has a queue, plus there is a list of nodes that have queued work.
Extensive use of Mutexes. Getting in shape for SMP.
Messages and data are deliverd in a new form. An Item now has
all information needed to queue such a request and deliver it later, so
it is now the basis of all data transfer since any transfer may need to
be queued.