From 70a0a592c2387b45f93615ce149e37500f8aea62 Mon Sep 17 00:00:00 2001
From: Ricard Illa <ricard@trkkn.com>
Date: Wed, 14 Sep 2022 15:31:54 +0200
Subject: [PATCH] ddns dag

---
 ddns/Makefile  | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++
 ddns/README.md |  5 ++++
 2 files changed, 69 insertions(+)
 create mode 100644 ddns/Makefile
 create mode 100644 ddns/README.md

diff --git a/ddns/Makefile b/ddns/Makefile
new file mode 100644
index 0000000..d7fb674
--- /dev/null
+++ b/ddns/Makefile
@@ -0,0 +1,64 @@
+DOMAIN_NAME ?= monotremata.xyz
+RECORD_NAME ?= wg
+
+API_URL = https://api.linode.com/v4
+GET_IP_URL = ifconfig.me/ip
+WORK_DIR = $(RECORD_NAME).$(DOMAIN_NAME)
+
+HOST_IP = $(WORK_DIR)/host_ip.txt
+DOMAIN_ID = $(WORK_DIR)/domain_id.txt
+RECORD_ID = $(WORK_DIR)/record_id.txt
+UPDATE_RECORD = $(WORK_DIR)/updated_record.txt
+
+TOKEN = $(shell pass linode.com/token)
+
+CURL = curl --silent
+AUTH_CURL = $(CURL) -H "Authorization: Bearer $(TOKEN)"
+
+define get_id
+	jq '.["data"][] | select(.["$(1)"] == "$(2)")["id"]'
+endef
+
+.PHONY: force clean
+
+# because the ip state is only updated when the IP changes, we should only need
+# to update the record when that happens
+$(UPDATE_RECORD): $(HOST_IP) $(DOMAIN_ID) $(RECORD_ID)
+	@echo "updating record"
+	@$(AUTH_CURL) \
+        -H "Content-Type: application/json" \
+        -X PUT -d '{ "target": "'"$$(cat $<)"'" }' \
+        "$(API_URL)/domains/$$(cat $(DOMAIN_ID))/records/$$(cat $(RECORD_ID))"
+	@touch $@
+
+# the domain id should not change and this should only ever need to run once
+$(DOMAIN_ID):
+	@echo "fetching domain id"
+	@mkdir -p $(@D)
+	@$(AUTH_CURL) $(API_URL)/domains | \
+	$(call get_id,domain,$(DOMAIN_NAME)) | \
+	tee $@
+
+# the register id should not change and this should only ever need to run once
+$(RECORD_ID): $(DOMAIN_ID)
+	@echo "fetching record id"
+	@mkdir -p $(@D)
+	@$(AUTH_CURL) $(API_URL)/domains/$$(cat $<)/records | \
+	$(call get_id,name,$(RECORD_NAME)) | \
+	tee $@
+
+# this target depends on a PHONY so that it is attempted every time, but the
+# target file should only be updated is the current host ip is different to the
+# saved one
+$(HOST_IP): force
+	@echo "fetching host IP"
+	@mkdir -p $(@D)
+	@current_ip=$$($(CURL) $(GET_IP_URL)); \
+	echo "$$current_ip"; \
+	if [ ! -f $@ ] || [ "$$current_ip" != "$$(cat $@)" ]; then \
+		echo "updating stored IP"; \
+		echo "$$current_ip" | tee $@; \
+	fi
+
+clean:
+	rm -r $(WORK_DIR)
diff --git a/ddns/README.md b/ddns/README.md
new file mode 100644
index 0000000..6850622
--- /dev/null
+++ b/ddns/README.md
@@ -0,0 +1,5 @@
+# DDNS
+
+This DAG updates a dynamic IP on Linode's DNS.
+
+It only attempts the update after the current IP has changed.