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Make all peer messages constant message size#8893

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rustyrussell wants to merge 11 commits intoElementsProject:masterfrom
rustyrussell:guilt/constant-message-size
Open

Make all peer messages constant message size#8893
rustyrussell wants to merge 11 commits intoElementsProject:masterfrom
rustyrussell:guilt/constant-message-size

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Not sufficient, but definitely necessary for avoiding trivial observation.

@rustyrussell rustyrussell added this to the v26.04 milestone Feb 10, 2026
@rustyrussell rustyrussell force-pushed the guilt/constant-message-size branch 10 times, most recently from 50d3283 to c949301 Compare February 12, 2026 11:25
This requires access to dumpcap.  On Ubuntu, at least, this means you
need to be in the "wireshark" group.

We may also need:
	sudo ethtool -K lo gro off gso off tso off

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Give us a single "next message" function to call.  This will be useful
when we want to write more than one at a time.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Do all the special treatment of the message type first.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This gives us finer control over write sizes: for now we just cap
the write size.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We're doing our own buffering now.

We leave the is_urgent() function for two commits in the future though.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
… count.

We are about to use them to make our packet size constant, and this
will upset the tests.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Messages are now constant.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: Protocol: we now pad all peer messages to make them the same length.
This replaces our previous nagle-based toggling.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
…ges.

Since we delay the others quite a lot (up to 1 second), it's better to consider
most messages "urgent" and worth immediately transmitting.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is exactly what membuf is for: it handles expansion much more
neatly.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
@rustyrussell rustyrussell force-pushed the guilt/constant-message-size branch from c949301 to 5132083 Compare February 13, 2026 03:46
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