Add checking for availability of ftl.pi-hole.net when using FTL from a custom branch. If the server is down (or the user is offline, cannot resolve the domain, etc.), we fail early and hard instead of possibly corrupting the installation

Signed-off-by: DL6ER <dl6er@dl6er.de>

advanced/Scripts/piholeCheckout.sh

@@ -164,7 +164,9 @@ checkout() {
         path="${2}/${binary}"
         oldbranch="$(pihole-FTL -b)"
 
-        if check_download_exists "$path"; then
+        check_download_exists "$path"
+        local ret=$?
+        if [ $ret -eq 0 ]; then
             echo "  ${TICK} Branch ${2} exists"
             echo "${2}" > /etc/pihole/ftlbranch
             chmod 644 /etc/pihole/ftlbranch
@@ -175,11 +177,19 @@ checkout() {
             # Update local and remote versions via updatechecker
             /opt/pihole/updatecheck.sh
         else
+            if [[ $ret -eq 1 ]]; then
                 echo "  ${CROSS} Requested branch \"${2}\" is not available"
                 ftlbranches=( $(git ls-remote https://github.com/pi-hole/ftl | grep 'heads' | sed 's/refs\/heads\///;s/ //g' | awk '{print $2}') )
                 echo -e "  ${INFO} Available branches for FTL are:"
                 for e in "${ftlbranches[@]}"; do echo "      - $e"; done
                 exit 1
+            elif [[ $ret -eq 2 ]]; then
+                printf "  %b Unable to download from ftl.pi-hole.net. Please check your Internet connection and try again later.\\n" "${CROSS}"
+                exit 1
+            else
+                printf "  %b Unknown error. Please contact Pi-hole Support\\n" "${CROSS}"
+                exit 1
+            fi
         fi
 
     else

advanced/Scripts/update.sh

@@ -144,7 +144,7 @@ main() {
     local binary
     binary="pihole-FTL${funcOutput##*pihole-FTL}" #binary name will be the last line of the output of get_binary_name (it always begins with pihole-FTL)
 
-    if FTLcheckUpdate "${binary}" > /dev/null; then
+    if FTLcheckUpdate "${binary}"; then
         FTL_update=true
         echo -e "  ${INFO} FTL:\\t\\t${COL_YELLOW}update available${COL_NC}"
     else
@@ -155,8 +155,13 @@ main() {
             2)
                 echo -e "  ${INFO} FTL:\\t\\t${COL_LIGHT_RED}Branch is not available.${COL_NC}\\n\\t\\t\\tUse ${COL_LIGHT_GREEN}pihole checkout ftl [branchname]${COL_NC} to switch to a valid branch."
                 ;;
+            3)
+                echo -e "  ${INFO} FTL:\\t\\t${COL_LIGHT_RED}Something has gone wrong, cannot reach download server${COL_NC}"
+                exit 1
+                ;;
             *)
                 echo -e "  ${INFO} FTL:\\t\\t${COL_LIGHT_RED}Something has gone wrong, contact support${COL_NC}"
+                exit 1
         esac
         FTL_update=false
     fi

automated install/basic-install.sh

@@ -1687,12 +1687,19 @@ update_dialogs() {
 }
 
 check_download_exists() {
+    # Check if the download exists and we can reach the server
     status=$(curl --head --silent "https://ftl.pi-hole.net/${1}" | head -n 1)
-    if grep -q "404" <<< "$status"; then
-        return 1
-    else
+
+    # Check the status code
+    if grep -q "200" <<< "$status"; then
         return 0
+    elif grep -q "404" <<< "$status"; then
+        return 1
     fi
+
+    # Other error or no status code at all, e.g., no Internet, server not
+    # available/reachable, ...
+    return 2
 }
 
 fully_fetch_repo() {
@@ -1959,8 +1966,6 @@ get_binary_name() {
 FTLcheckUpdate() {
     # In the next section we check to see if FTL is already installed (in case of pihole -r).
     # If the installed version matches the latest version, then check the installed sha1sum of the binary vs the remote sha1sum. If they do not match, then download
-    printf "  %b Checking for existing FTL binary...\\n" "${INFO}"
-
     local ftlLoc
     ftlLoc=$(command -v pihole-FTL 2>/dev/null)
 
@@ -1983,10 +1988,20 @@ FTLcheckUpdate() {
         local path
         path="${ftlBranch}/${binary}"
         # shellcheck disable=SC1090
-        if ! check_download_exists "$path"; then
+        check_download_exists "$path"
+        local ret=$?
+        if [ $ret -ne 0 ]; then
+            if [[ $ret -eq 1 ]]; then
                 printf "  %b Branch \"%s\" is not available.\\n" "${INFO}" "${ftlBranch}"
                 printf "  %b Use %bpihole checkout ftl [branchname]%b to switch to a valid branch.\\n" "${INFO}" "${COL_LIGHT_GREEN}" "${COL_NC}"
                 return 2
+            elif [[ $ret -eq 2 ]]; then
+                printf "  %b Unable to download from ftl.pi-hole.net. Please check your Internet connection and try again later.\\n" "${CROSS}"
+                return 3
+            else
+                printf "  %b Unknown error. Please contact Pi-hole Support\\n" "${CROSS}"
+                return 4
+            fi
         fi
 
         if [[ ${ftlLoc} ]]; then
@@ -2011,12 +2026,14 @@ FTLcheckUpdate() {
             FTLversion=$(/usr/bin/pihole-FTL tag)
             local FTLlatesttag
 
+            # Get the latest version from the GitHub API
             if ! FTLlatesttag=$(curl -sI https://github.com/pi-hole/FTL/releases/latest | grep --color=never -i Location: | awk -F / '{print $NF}' | tr -d '[:cntrl:]'); then
                 # There was an issue while retrieving the latest version
                 printf "  %b Failed to retrieve latest FTL release metadata" "${CROSS}"
                 return 3
             fi
 
+            # Check if the installed version matches the latest version
             if [[ "${FTLversion}" != "${FTLlatesttag}" ]]; then
                 return 0
             else