net: pump the network from the console wait (answer pings at the prompt)

A Game Boy sitting at the shell prompt now services the network instead of
being deaf until you run netd: KGetc (the console input wait) pumps net_pump
each poll, so inbound pings are auto-answered while idle. net_pump gained an
in-frame model and routes any non-framed link bytes to a small console-input
ring (con_push/con_pop), so a headless-injected command still reaches the shell
while SLIP frames go to the stack. Removes the old SLIP-skip-in-KGetc hack.

Verified: two Game Boys on the hub, GB0 idle at the prompt (no netd), GB1
`ping 10.0.0.2` -> 4/4 replies, routed GB1->hub->GB0->hub->GB1.

(Separate, pre-existing: gbhub *spawn* mode and windowed gbjoin can drop an idle
link socket - under investigation; daemon mode + headless is solid.)

1 files changed, 7 insertions, 31 deletions

diff --git a/src/syscall.asm b/src/syscall.asm
index 1051a4d..2adf5bf 100644
--- a/src/syscall.asm
+++ b/src/syscall.asm
@@ -132,41 +132,17 @@ KGetc::
     call pad_poll               ; poll joypad; drive the on-screen keyboard
     call osk_handle             ; CF set + A = byte if a key was typed
     jr c, .done
-    ld a, $80
-    ld [rSC], a
-    ld a, [rSC]
-    bit 7, a
-    jr nz, .yield
-    ld a, [rSB]                 ; A = serial byte
-    ; The link port is also the network. Skip SLIP frames (0xC0-delimited) so
-    ; inbound packets never surface as console input; plain bytes (an injected
-    ; command in headless use) still pass through.
-    ld b, a
-    ld a, [wConInSkip]
-    or a
-    jr nz, .inframe
-    ld a, b
-    cp SLIP_END
-    jr z, .frameopen
-    ld a, b                     ; ordinary byte -> console input
-    jr .done
-.frameopen
-    ld a, 1
-    ld [wConInSkip], a
-    jr .poll
-.inframe
-    ld a, b
-    cp SLIP_END
-    jr nz, .poll                ; still inside a frame -> discard
-    xor a
-    ld [wConInSkip], a          ; frame end -> resume
+    ; The link port is the network. Pump it here so the Game Boy services the
+    ; net (answers pings, etc.) while sitting at the prompt; net_pump routes any
+    ; non-framed link bytes (a headless-injected command) to the console ring.
+    call net_pump
+    call con_pop                ; queued console byte? CF clear -> return it
+    jr nc, .done
+    call SchedYield
     jr .poll
 .done
     and a                       ; CF = 0 (not EOF)
     ret
-.yield
-    call SchedYield
-    jr .poll
 
 ; -----------------------------------------------------------------------------
 ; KPutc(E = byte) - write to this process's stdout (console/file).