pool: wait to be paired before wrapping the rendezvous socket

Upstream #30 split rendezvous registration from waiting for a dial, so
RvServiceRegister now returns as soon as the relay lists the service and
no longer consumes the relay's 0x01 pairing byte. It updated its own
caller in net.cpp and left this one behind.

AcceptOneFn went straight from RvServiceRegister to BtfServiceWrap, so
BtfServiceWrap read that 0x01 as the first byte of the miner's 32-byte
ephemeral key and every byte after it was shifted by one. The X25519
handshake has no confirmation step, so it completed against a garbage
shared secret, the tunnel was handed to the Stratum event loop, and
nothing failed loudly: the pool logged a miner arriving and then dropped
it as "never authorized", while the miner logged a pool that closed on it
with gotSubscribeAck=0. Loopback miners were unaffected, which is exactly
what made it look like a relay problem.

Block in RvServiceWaitPaired before wrapping, and close and re-register if
the relay drops us first.

test_rvaccept.cpp covers both shapes against a real bitflashd on loopback:
the pre-fix order establishes a tunnel that carries no bytes, the fixed
order round-trips. Also corrects the btftunnel.h contract comment, which
still described the pre-#30 behaviour and is what the old code was written
against -- upstream's own test_relayproc.cpp, test_btftunnel.cpp and
test_btfrv.cpp are still on that stale contract and fail the same way.

(cherry picked from commit 3e3a36b2bf1e6ffb4861507089b743688619377f)

1 files changed, 9 insertions, 4 deletions

diff --git a/src/btftunnel.h b/src/btftunnel.h
index 1fa4f01..24a7509 100644
--- a/src/btftunnel.h
+++ b/src/btftunnel.h
@@ -10,8 +10,12 @@
 // caller), then BtfClientTunnel connects through the relay, runs the echan
 // handshake, and returns a local SOCKET to hand a new outbound CNode.
 //
-// Service side: after RvServiceRegister pairs us with a client, BtfServiceWrap
-// completes the echan handshake and returns a local SOCKET for an inbound CNode.
+// Service side: RvServiceRegister only registers -- callers must then block in
+// RvServiceWaitPaired until a client is actually paired to them. BtfServiceWrap
+// completes the echan handshake on that paired socket and returns a local
+// SOCKET for an inbound CNode. Wrapping a registered-but-unpaired socket reads
+// the relay's 0x01 pairing byte as the first byte of the client's ephemeral
+// key, which silently corrupts the tunnel instead of failing.
 
 #ifndef BITFLASH_BTFTUNNEL_H
 #define BITFLASH_BTFTUNNEL_H
@@ -39,8 +43,9 @@ btf_socket_t BtfClientTunnel(const char* meeting_host, unsigned short port,
                              const unsigned char target_pubkey[32],
                              const unsigned char service_enc_pub[32]);
 
-// Service: wrap an already-paired rendezvous socket (from RvServiceRegister)
-// with echan using my static x25519 secret, returning a local plaintext SOCKET
+// Service: wrap an already-paired rendezvous socket (RvServiceRegister followed
+// by RvServiceWaitPaired -- the pairing byte MUST already be consumed) with
+// echan using my static x25519 secret, returning a local plaintext SOCKET
 // for an inbound CNode. Consumes `rv` (closed when the tunnel tears down).
 btf_socket_t BtfServiceWrap(RvSocket rv, const unsigned char my_enc_sk[32]);