From 4115f2ab9572dc23acaf4cd0b1a95f67ee38c92b Mon Sep 17 00:00:00 2001
From: Lu Wang <rebmit@rebmit.moe>
Date: Wed, 15 Jan 2025 17:43:54 +0800
Subject: [PATCH] services/enthalpy: enable etx link quality estimation

---
 flake/nixpkgs.nix                             |   5 +
 nixos/modules/services/enthalpy/bird.nix      |   1 +
 .../bird-babel-link-quality-estimation.patch  | 135 ++++++++++++++++++
 3 files changed, 141 insertions(+)
 create mode 100644 patches/bird-babel-link-quality-estimation.patch

diff --git a/flake/nixpkgs.nix b/flake/nixpkgs.nix
index 21ec8bb..bf9de27 100644
--- a/flake/nixpkgs.nix
+++ b/flake/nixpkgs.nix
@@ -8,6 +8,11 @@ let
     inputs.nixpkgs-terraform-providers-bin.overlay
 
     (_final: prev: {
+      bird = prev.bird.overrideAttrs (old: {
+        patches = (old.patches or [ ]) ++ [
+          ../patches/bird-babel-link-quality-estimation.patch
+        ];
+      });
       mautrix-telegram = prev.mautrix-telegram.overrideAttrs (old: {
         patches = (old.patches or [ ]) ++ [
           ../patches/mautrix-telegram-sticker.patch
diff --git a/nixos/modules/services/enthalpy/bird.nix b/nixos/modules/services/enthalpy/bird.nix
index 8e08313..b477c90 100644
--- a/nixos/modules/services/enthalpy/bird.nix
+++ b/nixos/modules/services/enthalpy/bird.nix
@@ -117,6 +117,7 @@ in
         randomize router id;
         interface "enta*" {
           type tunnel;
+          link quality etx;
           rxcost 32;
           rtt cost 1024;
           rtt max 1024 ms;
diff --git a/patches/bird-babel-link-quality-estimation.patch b/patches/bird-babel-link-quality-estimation.patch
new file mode 100644
index 0000000..0c6bcb1
--- /dev/null
+++ b/patches/bird-babel-link-quality-estimation.patch
@@ -0,0 +1,135 @@
+From 700a4fddd3b554cc1071608cf8d945400ae35c9e Mon Sep 17 00:00:00 2001
+From: Nick Cao <nickcao@nichi.co>
+Date: Fri, 23 Jun 2023 10:36:48 +0800
+Subject: [PATCH] Babel: allow choosing link quality estimation algorithm
+
+ETX link quality estimation algorithm is useful for link types other than wireless,
+especially when using babel with tunnels where packet losses do occur.
+---
+ doc/bird.sgml        | 10 ++++++++++
+ proto/babel/babel.c  |  8 +++-----
+ proto/babel/babel.h  |  8 ++++++++
+ proto/babel/config.Y |  8 +++++++-
+ 4 files changed, 28 insertions(+), 6 deletions(-)
+
+diff --git a/doc/bird.sgml b/doc/bird.sgml
+index 7abb8348c..fb00b9fca 100644
+--- a/doc/bird.sgml
++++ b/doc/bird.sgml
+@@ -2320,6 +2320,7 @@ protocol babel [<name>] {
+ 		rx buffer <number>;
+ 		tx length <number>;
+ 		check link <switch>;
++		link quality <none|etx>;
+ 		next hop ipv4 <address>;
+ 		next hop ipv6 <address>;
+ 		extended next hop <switch>;
+@@ -2423,6 +2424,15 @@ protocol babel [<name>] {
+       hardware drivers or platforms do not implement this feature. Default:
+       yes.
+ 
++      <tag><label id="babel-link-quality">link quality none|etx </tag>
++      This option specifies the link quality estimation algorithm for computing
++      costs based on Hello history: none or etx. The none (k-out-of-j) algorithm
++      is suitable for wired links that are either up, in which case they only
++      occasionally drop a packet, or down, in which case they drop all packets.
++      The Expected Transmission Cost algorithm, or etx, is suitable for wireless
++      links that exhibit continuous variation of the link quality. Default: etx for
++      wireless interfaces, none otherwise.
++
+       <tag><label id="babel-next-hop-ipv4">next hop ipv4 <m/address/</tag>
+       Set the next hop address advertised for IPv4 routes advertised on this
+       interface. Default: the preferred IPv4 address of the interface.
+diff --git a/proto/babel/babel.c b/proto/babel/babel.c
+index b5cbb63f8..c5d8cbc0b 100644
+--- a/proto/babel/babel.c
++++ b/proto/babel/babel.c
+@@ -593,10 +593,9 @@ babel_update_cost(struct babel_neighbor *nbr)
+   if (!rcv || !nbr->ifa->up)
+     goto done;
+ 
+-  switch (cf->type)
++  switch (cf->link_quality)
+   {
+-  case BABEL_IFACE_TYPE_WIRED:
+-  case BABEL_IFACE_TYPE_TUNNEL:
++  case BABEL_IFACE_LINK_QUALITY_NONE:
+     /* k-out-of-j selection - Appendix 2.1 in the RFC. */
+ 
+     /* Link is bad if less than cf->limit/16 of expected hellos were received */
+@@ -606,8 +605,7 @@ babel_update_cost(struct babel_neighbor *nbr)
+     rxcost =  cf->rxcost;
+     txcost = nbr->txcost;
+     break;
+-
+-  case BABEL_IFACE_TYPE_WIRELESS:
++  case BABEL_IFACE_LINK_QUALITY_ETX:
+     /*
+      * ETX - Appendix 2.2 in the RFC.
+      *
+diff --git a/proto/babel/babel.h b/proto/babel/babel.h
+index edde4cabe..6a2968f10 100644
+--- a/proto/babel/babel.h
++++ b/proto/babel/babel.h
+@@ -118,6 +118,13 @@ enum babel_iface_type {
+   BABEL_IFACE_TYPE_MAX
+ };
+ 
++enum babel_iface_link_quality {
++  BABEL_IFACE_LINK_QUALITY_UNDEF	= 0,
++  BABEL_IFACE_LINK_QUALITY_NONE	= 1,
++  BABEL_IFACE_LINK_QUALITY_ETX		= 2,
++  BABEL_IFACE_LINK_QUALITY_MAX
++};
++
+ enum babel_ae_type {
+   BABEL_AE_WILDCARD		= 0,
+   BABEL_AE_IP4			= 1,
+@@ -145,6 +152,7 @@ struct babel_iface_config {
+   u8 type;
+   u8 limit;				/* Minimum number of Hellos to keep link up */
+   u8 check_link;
++  u8 link_quality;
+   uint port;
+   uint hello_interval;			/* Hello interval, in us */
+   uint ihu_interval;			/* IHU interval, in us */
+diff --git a/proto/babel/config.Y b/proto/babel/config.Y
+index d412a54b5..623e74b24 100644
+--- a/proto/babel/config.Y
++++ b/proto/babel/config.Y
+@@ -26,7 +26,7 @@ CF_KEYWORDS(BABEL, INTERFACE, METRIC, RXCOST, HELLO, UPDATE, INTERVAL, PORT,
+ 	TYPE, WIRED, WIRELESS, RX, TX, BUFFER, PRIORITY, LENGTH, CHECK, LINK,
+ 	NEXT, HOP, IPV4, IPV6, BABEL_METRIC, SHOW, INTERFACES, NEIGHBORS,
+ 	ENTRIES, RANDOMIZE, ROUTER, ID, AUTHENTICATION, NONE, MAC, PERMISSIVE,
+-	EXTENDED, TUNNEL, RTT, MIN, MAX, DECAY, SEND, TIMESTAMPS, COST, DELAY)
++	EXTENDED, TUNNEL, RTT, MIN, MAX, DECAY, SEND, TIMESTAMPS, COST, DELAY, QUALITY, ETX)
+ 
+ CF_GRAMMAR
+ 
+@@ -84,6 +84,8 @@ babel_iface_finish:
+       BABEL_IFACE->hello_interval = BABEL_HELLO_INTERVAL_WIRELESS;
+     if (!BABEL_IFACE->rxcost)
+       BABEL_IFACE->rxcost = BABEL_RXCOST_WIRELESS;
++    if (!BABEL_IFACE->link_quality)
++      BABEL_IFACE->link_quality = BABEL_IFACE_LINK_QUALITY_ETX;
+   }
+   else
+   {
+@@ -93,6 +95,8 @@ babel_iface_finish:
+       BABEL_IFACE->rxcost = BABEL_RXCOST_WIRED;
+     if (BABEL_IFACE->type == BABEL_IFACE_TYPE_TUNNEL && !BABEL_IFACE->rtt_cost)
+       BABEL_IFACE->rtt_cost = BABEL_RXCOST_RTT;
++    if (!BABEL_IFACE->link_quality)
++      BABEL_IFACE->link_quality = BABEL_IFACE_LINK_QUALITY_NONE;
+   }
+ 
+   if (BABEL_IFACE->rtt_cost && !BABEL_IFACE->rtt_send)
+@@ -156,6 +160,8 @@ babel_iface_item:
+  | TX tos { BABEL_IFACE->tx_tos = $2; }
+  | TX PRIORITY expr { BABEL_IFACE->tx_priority = $3; }
+  | CHECK LINK bool { BABEL_IFACE->check_link = $3; }
++ | LINK QUALITY NONE { BABEL_IFACE->link_quality = BABEL_IFACE_LINK_QUALITY_NONE; }
++ | LINK QUALITY ETX { BABEL_IFACE->link_quality = BABEL_IFACE_LINK_QUALITY_ETX; }
+  | NEXT HOP IPV4 ipa { BABEL_IFACE->next_hop_ip4 = $4; if (!ipa_is_ip4($4)) cf_error("Must be an IPv4 address"); }
+  | NEXT HOP IPV6 ipa { BABEL_IFACE->next_hop_ip6 = $4; if (!ipa_is_ip6($4)) cf_error("Must be an IPv6 address"); }
+  | EXTENDED NEXT HOP bool { BABEL_IFACE->ext_next_hop = $4; }