Merge pull request #753 from j1elo/master

Use DNS requests to discover external IP address

.dockerignore

@@ -2,6 +2,7 @@
 
 !docker/coturn/alpine/
 !docker/coturn/debian/
+!docker/coturn/rootfs/
 
 !cmake/
 !CMakeLists.txt

docker/coturn/CHANGELOG.md

@@ -11,10 +11,15 @@ Coturn TURN server Docker image changelog
 
 - [Prometheus] support with [prometheus-client-c] 0.1.3: <https://github.com/digitalocean/prometheus-client-c/releases/tag/v0.1.3> ([#754])
 
+### Improved
+
+- Use DNS requests to discover external IP address in `detect-external-ip` script ([#753]).
+
 ### Fixed
 
 - Incorrect linking with [mongo-c-driver] on [Debian Linux] image.
 
+[#753]: /../../pull/753
 [#754]: /../../pull/754
 
 

docker/coturn/Makefile

@@ -176,6 +176,7 @@ docker.push:
 #		[( [build=no]
 #		 | build=yes [DOCKERFILE=(debian|alpine)]
 #		             [ref=<git-ref>] )]
+#		[with=ipv6]
 
 test-docker-platforms = $(strip $(if $(call eq,$(platforms),),$(MAIN_PLATFORM),\
                                 $(if $(call eq,$(platforms),@all),$(PLATFORMS),\
@@ -195,6 +196,7 @@ define test.docker.do
 		@make docker.image DOCKERFILE=$(DOCKERFILE) \
 			no-cache=no tag=$(tag) platform=$(platform) ref=$(ref) ,)
 	IMAGE=coturn/$(NAME):$(tag) PLATFORM=$(platform) \
+	$(if $(call eq,$(with),ipv6),TEST_IPV6=1,) \
 	node_modules/.bin/bats \
 		--timing $(if $(call eq,$(CI),),--pretty,--formatter tap) \
 		tests/main.bats

docker/coturn/README.md

@@ -110,6 +110,14 @@ docker run -d --network=host coturn/coturn \
            --relay-ip='$(detect-external-ip)'
 ```
 
+By default, [IPv4] address is discovered. In case you need an [IPv6] one, specify the `--ipv6` flag:
+```bash
+docker run -d --network=host coturn/coturn \
+           -n --log-file=stdout \
+           --external-ip='$(detect-external-ip --ipv6)' \
+           --relay-ip='$(detect-external-ip --ipv6)'
+```
+
 
 ### Persistence
 
@@ -185,6 +193,8 @@ If you have any problems with or questions about this image, please contact us t
 
 
 [DockerHub]: https://hub.docker.com
+[IPv4]: https://en.wikipedia.org/wiki/IPv4
+[IPv6]: https://en.wikipedia.org/wiki/IPv6
 [RFC 5766 Section 6.2]: https://tools.ietf.org/html/rfc5766.html#section-6.2
 
 [1]: http://alpinelinux.org

docker/coturn/alpine/Dockerfile

@@ -150,6 +150,7 @@ RUN mkdir -p /out/ \
  && rm -f /out/etc/coturn/turnserver.conf.default
 
 # Install helper tools of Docker image.
+COPY docker/coturn/rootfs/ /out/
 COPY docker/coturn/alpine/rootfs/ /out/
 RUN chmod +x /out/usr/local/bin/docker-entrypoint.sh \
              /out/usr/local/bin/detect-external-ip.sh
@@ -185,6 +186,9 @@ RUN apk update \
         hiredis \
         mongo-c-driver \
         libmicrohttpd \
+ # Install `dig` tool for `detect-external-ip.sh`.
+ && apk add --no-cache \
+        bind-tools \
  # Cleanup unnecessary stuff.
  && rm -rf /var/cache/apk/*
 

docker/coturn/alpine/rootfs/usr/local/bin/detect-external-ip.sh

@@ -1,7 +0,0 @@
-#!/bin/sh
-
-if [ -z "$REAL_EXTERNAL_IP" ]; then
-  export REAL_EXTERNAL_IP="$(curl -4 https://icanhazip.com 2>/dev/null)"
-fi
-
-exec echo "$REAL_EXTERNAL_IP"

docker/coturn/debian/Dockerfile

@@ -207,6 +207,7 @@ RUN mkdir -p /out/ \
  && rm -f /out/etc/coturn/turnserver.conf.default
 
 # Install helper tools of Docker image.
+COPY docker/coturn/rootfs/ /out/
 COPY docker/coturn/debian/rootfs/ /out/
 RUN chmod +x /out/usr/local/bin/docker-entrypoint.sh \
              /out/usr/local/bin/detect-external-ip.sh
@@ -246,6 +247,9 @@ RUN apt-get update \
             libpq5 libmariadb3 libsqlite3-0 \
             libhiredis0.14 \
             libmicrohttpd12 \
+ # Install `dig` tool for `detect-external-ip.sh`.
+ && apt-get install -y --no-install-recommends --no-install-suggests \
+            dnsutils \
  # Cleanup unnecessary stuff.
  && rm -rf /var/lib/apt/lists/*
 

docker/coturn/debian/rootfs/usr/local/bin/detect-external-ip.sh

@@ -1,7 +0,0 @@
-#!/bin/sh
-
-if [ -z "$REAL_EXTERNAL_IP" ]; then
-  export REAL_EXTERNAL_IP="$(curl -4 https://icanhazip.com 2>/dev/null)"
-fi
-
-exec echo "$REAL_EXTERNAL_IP"

docker/coturn/rootfs/usr/local/bin/detect-external-ip.sh

@@ -0,0 +1,112 @@
+#!/usr/bin/env sh
+# shellcheck shell=dash
+
+#/ Use DNS to find out about the external IP of the running system.
+#/
+#/ This script is useful when running from a machine that sits behind a NAT.
+#/ Due to how NAT works, machines behind it belong to an internal or private
+#/ subnet, with a different address space than the external or public side.
+#/
+#/ Typically it is possible to make an HTTP request to a number of providers
+#/ that offer the external IP in their response body (eg: ifconfig.me). However,
+#/ why do a slow and heavy HTTP request, when DNS exists and is much faster?
+#/ Well established providers such as OpenDNS or Google offer special hostnames
+#/ that, when resolved, will actually return the IP address of the caller.
+#/
+#/ https://unix.stackexchange.com/questions/22615/how-can-i-get-my-external-ip-address-in-a-shell-script/81699#81699
+#/
+#/
+#/ Arguments
+#/ ---------
+#/
+#/ --ipv4
+#/
+#/   Find the external IPv4 address.
+#/   Optional. Default: Enabled.
+#/
+#/ --ipv6
+#/
+#/   Find the external IPv6 address.
+#/   Optional. Default: Disabled.
+
+
+
+# Shell setup
+# ===========
+
+# Shell options for strict error checking.
+for OPTION in errexit errtrace pipefail nounset; do
+  set -o | grep -wq "$OPTION" && set -o "$OPTION"
+done
+
+# Trace all commands (to stderr).
+#set -o xtrace
+
+
+
+# Shortcut: REAL_EXTERNAL_IP
+# ==========================
+
+if [ -n "${REAL_EXTERNAL_IP:-}" ]; then
+  echo "$REAL_EXTERNAL_IP"
+  exit 0
+fi
+
+
+
+# Parse call arguments
+# ====================
+
+CFG_IPV4="true"
+
+while [ $# -gt 0 ]; do
+  case "${1-}" in
+    --ipv4) CFG_IPV4="true" ;;
+    --ipv6) CFG_IPV4="false" ;;
+    *)
+      echo "Invalid argument: '${1-}'" >&2
+      exit 1
+      ;;
+  esac
+  shift
+done
+
+
+
+# Discover the external IP address
+# ================================
+
+if [ "$CFG_IPV4" = "true" ]; then
+  COMMANDS='dig @resolver1.opendns.com myip.opendns.com A -4 +short
+            dig @ns1.google.com o-o.myaddr.l.google.com TXT -4 +short | tr -d \"
+            dig @1.1.1.1 whoami.cloudflare TXT CH -4 +short | tr -d \"
+            dig @ns1-1.akamaitech.net whoami.akamai.net A -4 +short'
+
+  is_valid_ip() {
+    # Check if the input looks like an IPv4 address.
+    # Doesn't check if the actual values are valid; assumes they are.
+    echo "$1" | grep -Eq '^([0-9]{1,3}\.){3}[0-9]{1,3}$'
+  }
+else
+  COMMANDS='dig @resolver1.opendns.com myip.opendns.com AAAA -6 +short
+            dig @ns1.google.com o-o.myaddr.l.google.com TXT -6 +short | tr -d \"
+            dig @2606:4700:4700::1111 whoami.cloudflare TXT CH -6 +short | tr -d \"'
+
+  is_valid_ip() {
+    # Check if the input looks like an IPv6 address.
+    # It's almost impossible to check the IPv6 representation because it
+    # varies wildly, so just check that there are at least 2 colons.
+    [ "$(echo "$1" | awk -F':' '{print NF-1}')" -ge 2 ]
+  }
+fi
+
+IFS="$(printf '\nx')" && IFS="${IFS%x}"
+for COMMAND in $COMMANDS; do
+  if IP="$(eval "$COMMAND")" && is_valid_ip "$IP"; then
+    printf '%s' "$IP"
+    exit 0
+  fi
+done
+
+echo "[$0] All providers failed" >&2
+exit 1

docker/coturn/tests/main.bats

@@ -125,3 +125,78 @@
   [ "$status" -eq 0 ]
   [ ! "$output" = '' ]
 }
+
+
+@test "detect-external-ip is present" {
+  run docker run --rm --platform $PLATFORM --entrypoint sh $IMAGE -c \
+    'which detect-external-ip'
+  [ "$status" -eq 0 ]
+}
+
+@test "detect-external-ip runs ok" {
+  run docker run --rm --platform $PLATFORM --entrypoint sh $IMAGE -c \
+    'detect-external-ip'
+  [ "$status" -eq 0 ]
+}
+
+@test "detect-external-ip returns valid IPv4" {
+  run docker run --rm --platform $PLATFORM --entrypoint sh $IMAGE -c \
+    'detect-external-ip --ipv4'
+  [ "$status" -eq 0 ]
+
+  run validate_ipv4 "$output"
+  [ "$status" -eq 0 ]
+}
+
+@test "detect-external-ip returns valid IPv6" {
+  [ -z "$TEST_IPV6" ] && skip
+
+  run docker run --rm --platform $PLATFORM --entrypoint sh $IMAGE -c \
+    'detect-external-ip --ipv6'
+  [ "$status" -eq 0 ]
+
+  run validate_ipv6 "$output"
+  [ "$status" -eq 0 ]
+}
+
+@test "detect-external-ip returns IPv4 by default" {
+  run docker run --rm --platform $PLATFORM --entrypoint sh $IMAGE -c \
+    'detect-external-ip --ipv4'
+  [ "$status" -eq 0 ]
+
+  run validate_ipv4 "$output"
+  [ "$status" -eq 0 ]
+}
+
+
+#
+# Helpers
+#
+
+# Tests the IP address to be a valid IPv4 address.
+function validate_ipv4() {
+  local ip=$1
+  local stat=1
+
+  if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
+    OIFS=$IFS
+    IFS='.'
+    ip=($ip)
+    IFS=$OIFS
+    [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
+    && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
+    stat=$?
+  fi
+  return $stat
+}
+
+# Tests the IP address to be a valid IPv6 address.
+function validate_ipv6() {
+  local ip=$1
+  local stat=1
+
+  if [[ $ip =~ ^([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}$ ]]; then
+    stat=0
+  fi
+  return $stat
+}