From 8d3574e183a92b230524216e181dd5c4ab6ac71e Mon Sep 17 00:00:00 2001
From: mjallen18 <matt.l.jallen@gmail.com>
Date: Tue, 10 Mar 2026 12:32:49 -0500
Subject: [PATCH] kek

---
 .../asahi-tcp-cong-wants-ce-events.patch      | 32 +++++++++++++++++++
 packages/linux-cachyos/prepare.nix            |  9 +++++-
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 packages/linux-cachyos/patches/asahi-tcp-cong-wants-ce-events.patch

diff --git a/packages/linux-cachyos/patches/asahi-tcp-cong-wants-ce-events.patch b/packages/linux-cachyos/patches/asahi-tcp-cong-wants-ce-events.patch
new file mode 100644
index 0000000..3852458
--- /dev/null
+++ b/packages/linux-cachyos/patches/asahi-tcp-cong-wants-ce-events.patch
@@ -0,0 +1,32 @@
+From: CachyOS/NixOS-CachyOS
+Subject: [PATCH] net/tcp: add TCP_CONG_WANTS_CE_EVENTS for Asahi tree compat
+
+The CachyOS 6.18 base patch adds TCP_CONG_WANTS_CE_EVENTS at BIT(2) and
+a tcp_ca_wants_ce_events() helper in include/net/tcp.h, and updates
+tcp_bbr.c and tcp_input.c to use them.
+
+The Asahi linux tree already occupies BIT(2)–BIT(4) with AccECN flags
+(TCP_CONG_NEEDS_ACCECN, TCP_CONG_ECT_1_NEGOTIATION,
+TCP_CONG_NO_FALLBACK_RFC3168), so the CachyOS hunk that defines
+TCP_CONG_WANTS_CE_EVENTS fails to apply, while the later hunks that
+*use* it (tcp_ca_wants_ce_events(), tcp_bbr.c .flags) succeed, leaving
+a dangling undefined-identifier compile error.
+
+Fix: define TCP_CONG_WANTS_CE_EVENTS at BIT(5) (the next free bit after
+the AccECN flags) and add it to TCP_CONG_MASK. The tcp_ca_wants_ce_events()
+helper and tcp_bbr.c / tcp_input.c callers are already in place from the
+CachyOS patch, so this is sufficient to resolve the build error.
+
+--- a/include/net/tcp.h
++++ b/include/net/tcp.h
+@@ -1198,6 +1198,10 @@ enum tcp_ca_ack_event_flags {
+ /* Cannot fallback to RFC3168 during AccECN negotiation */
+ #define TCP_CONG_NO_FALLBACK_RFC3168	BIT(4)
++/* Wants notification of CE events (CA_EVENT_ECN_IS_CE, CA_EVENT_ECN_NO_CE).
++ * BIT(2)–BIT(4) are taken by AccECN flags in the Asahi tree. */
++#define TCP_CONG_WANTS_CE_EVENTS	BIT(5)
+ #define TCP_CONG_MASK  (TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN | \
+-			TCP_CONG_NEEDS_ACCECN | TCP_CONG_ECT_1_NEGOTIATION | \
+-			TCP_CONG_NO_FALLBACK_RFC3168)
++			TCP_CONG_NEEDS_ACCECN | TCP_CONG_ECT_1_NEGOTIATION | \
++			TCP_CONG_NO_FALLBACK_RFC3168 | TCP_CONG_WANTS_CE_EVENTS)
diff --git a/packages/linux-cachyos/prepare.nix b/packages/linux-cachyos/prepare.nix
index 400278e..8deeb06 100644
--- a/packages/linux-cachyos/prepare.nix
+++ b/packages/linux-cachyos/prepare.nix
@@ -95,7 +95,14 @@ let
   ++ schedPatches
   ++ lib.optional (
     cachyConfig.cpuSched == "hardened"
-  ) "${patches-src}/${majorMinor}/misc/0001-hardened.patch";
+  ) "${patches-src}/${majorMinor}/misc/0001-hardened.patch"
+  # The Asahi tree occupies BIT(2)–BIT(4) in TCP_CONG_MASK with AccECN flags,
+  # so the CachyOS hunk defining TCP_CONG_WANTS_CE_EVENTS at BIT(2) fails to
+  # apply while later hunks that use it succeed — causing a compile error.
+  # This patch places the symbol at BIT(5) and adds it to TCP_CONG_MASK.
+  ++ lib.optional (
+    cachyConfig.taste == "linux-cachyos-asahi"
+  ) ./patches/asahi-tcp-cong-wants-ce-events.patch;
 
   # There are some configurations set by the PKGBUILD
   pkgbuildConfig =