Rework zed_notify_email for configurable PROG/OPTS

This commit reworks the zed_notify_email() function to allow
configuration of the mail executable and command-line arguments.

ZED_EMAIL_PROG specifies the name or path of the executable responsible
for sending notifications via email.  This variable defaults to "mail".

ZED_EMAIL_OPTS specifies command-line options passed to ZED_EMAIL_PROG.
The following keyword substitutions are performed:
- @ADDRESS@ is replaced with the recipient email address(es)
- @SUBJECT@ is replaced with the notification subject
This variable defaults to "-s '@SUBJECT@' @ADDRESS@".

ZED_EMAIL_ADDR replaces ZED_EMAIL (although the latter is retained
for backward compatibility).  This variable can contain multiple
addresses as long as they are delimited by whitespace.

Signed-off-by: Chris Dunlap <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #3634
Closes #3631

2 files changed, 51 insertions, 11 deletions

diff --git a/cmd/zed/zed.d/zed-functions.sh b/cmd/zed/zed.d/zed-functions.sh
index 83c36ba6f..1ddafa99f 100644
--- a/cmd/zed/zed.d/zed-functions.sh
+++ b/cmd/zed/zed.d/zed-functions.sh
@@ -207,16 +207,25 @@ zed_notify()
 
 # zed_notify_email (subject, pathname)
 #
-# Send a notification via email to the address specified by ZED_EMAIL.
+# Send a notification via email to the address specified by ZED_EMAIL_ADDR.
 #
-# Requires the mail executable to be installed in the standard PATH.
+# Requires the mail executable to be installed in the standard PATH, or
+# ZED_EMAIL_PROG to be defined with the pathname of an executable capable of
+# reading a message body from stdin.
+#
+# Command-line options to the mail executable can be specified in
+# ZED_EMAIL_OPTS.  This undergoes the following keyword substitutions:
+# - @ADDRESS@ is replaced with the space-delimited recipient email address(es)
+# - @SUBJECT@ is replaced with the notification subject
 #
 # Arguments
 #   subject: notification subject
 #   pathname: pathname containing the notification message (OPTIONAL)
 #
 # Globals
-#   ZED_EMAIL
+#   ZED_EMAIL_PROG
+#   ZED_EMAIL_OPTS
+#   ZED_EMAIL_ADDR
 #
 # Return
 #   0: notification sent
@@ -228,19 +237,33 @@ zed_notify_email()
     local subject="$1"
     local pathname="${2:-"/dev/null"}"
 
-    [ -n "${ZED_EMAIL}" ] || return 2
+    : "${ZED_EMAIL_PROG:="mail"}"
+    : "${ZED_EMAIL_OPTS:="-s '@SUBJECT@' @ADDRESS@"}"
+
+    # For backward compatibility with ZED_EMAIL.
+    if [ -n "${ZED_EMAIL}" ] && [ -z "${ZED_EMAIL_ADDR}" ]; then
+        ZED_EMAIL_ADDR="${ZED_EMAIL}"
+    fi
+    [ -n "${ZED_EMAIL_ADDR}" ] || return 2
+
+    zed_check_cmd "${ZED_EMAIL_PROG}" || return 1
 
     [ -n "${subject}" ] || return 1
     if [ ! -r "${pathname}" ]; then
-        zed_log_err "mail cannot read \"${pathname}\""
+        zed_log_err \
+                "$(basename "${ZED_EMAIL_PROG}") cannot read \"${pathname}\""
         return 1
     fi
 
-    zed_check_cmd "mail" || return 1
+    ZED_EMAIL_OPTS="$(echo "${ZED_EMAIL_OPTS}" \
+        | sed   -e "s/@ADDRESS@/${ZED_EMAIL_ADDR}/g" \
+                -e "s/@SUBJECT@/${subject}/g")"
 
-    mail -s "${subject}" "${ZED_EMAIL}" < "${pathname}" >/dev/null 2>&1; rv=$?
+    # shellcheck disable=SC2086
+    eval "${ZED_EMAIL_PROG}" ${ZED_EMAIL_OPTS} < "${pathname}" >/dev/null 2>&1
+    rv=$?
     if [ "${rv}" -ne 0 ]; then
-        zed_log_err "mail exit=${rv}"
+        zed_log_err "$(basename "${ZED_EMAIL_PROG}") exit=${rv}"
         return 1
     fi
     return 0
diff --git a/cmd/zed/zed.d/zed.rc b/cmd/zed/zed.d/zed.rc
index c2336287f..f80fa3338 100644
--- a/cmd/zed/zed.d/zed.rc
+++ b/cmd/zed/zed.d/zed.rc
@@ -10,11 +10,28 @@
 #ZED_DEBUG_LOG="/tmp/zed.debug.log"
 
 ##
-# Email address of the zpool administrator for receipt of notifications.
-#   Email will only be sent if ZED_EMAIL is defined.
+# Email address of the zpool administrator for receipt of notifications;
+#   multiple addresses can be specified if they are delimited by whitespace.
+# Email will only be sent if ZED_EMAIL_ADDR is defined.
 # Disabled by default; uncomment to enable.
 #
-#ZED_EMAIL="root"
+#ZED_EMAIL_ADDR="root"
+
+##
+# Name or path of executable responsible for sending notifications via email;
+#   the mail program must be capable of reading a message body from stdin.
+# Email will only be sent if ZED_EMAIL_ADDR is defined.
+#
+#ZED_EMAIL_PROG="mail"
+
+##
+# Command-line options for ZED_EMAIL_PROG.
+# The string @ADDRESS@ will be replaced with the recipient email address(es).
+# The string @SUBJECT@ will be replaced with the notification subject;
+#   this should be protected with quotes to prevent word-splitting.
+# Email will only be sent if ZED_EMAIL_ADDR is defined.
+#
+#ZED_EMAIL_OPTS="-s '@SUBJECT@' @ADDRESS@"
 
 ##
 # Default directory for zed lock files.