[mike@mwxm4]

creds.go

@@ -91,7 +91,10 @@ func getcreds() (string, string) { // ----------------------------------- the lo
   c,plain,err:=readcreds(path)
   if err==nil {
     if (plain) {                                       // written before ~/.dnsrc was encrypted: put it away properly
-      if err:=writecreds(path,c); err!=nil { PE("cannot encrypt "+path,err.Error()) } else { PO(path+" is now encrypted") }
+      err:=writecreds(path,c)
+      if (!jsonmode()) {                                  // a machine gets the answer to what it asked, nothing else
+        if err!=nil { PE("cannot encrypt "+path,err.Error()) } else { PO(path+" is now encrypted") }
+      }
     }
     return c.User,c.Pass
   }
@@ -99,16 +102,16 @@ func getcreds() (string, string) { // ----------------------------------- the lo
   // A file that is there but will not open — meddled with, truncated, written
   // by a build with a different FILEKEY — is worth saying out loud before the
   // passphrase is asked for and the file written afresh.
-  if (!os.IsNotExist(err)) { PE("cannot read "+path,err.Error()) }
+  if (!os.IsNotExist(err) && !jsonmode()) { PE("cannot read "+path,err.Error()) }
 
   if (SEALED=="") {
-    PE("this build carries no credentials","run 'dns --seal' and paste the line into creds.go")
-    os.Exit(1)
+    Fatal("this build carries no credentials","run 'dns --seal' and paste the line into creds.go")
   }
 
-  if (!oninteractive()) {
-    PE("no credentials in "+path,"run dns once by hand to unseal them")
-    os.Exit(1)
+  // A json run asks nothing either: the passphrase prompt would land in the
+  // middle of the answer, and whoever is reading it cannot type.
+  if (!oninteractive() || jsonmode()) {
+    Fatal("no credentials in "+path,"run dns once by hand to unseal them")
   }
 
   c=askpassphrase()
@@ -251,7 +254,7 @@ func filegcm(salt []byte) (cipher.AEAD, error) { // ----------------------------
 
 func credspath() string { // -------------------------------------------------------------------- where the file is
   home,err:=os.UserHomeDir()
-  if err!=nil { PE("cannot find the home directory",err.Error()); os.Exit(1) }
+  if err!=nil { Fatal("cannot find the home directory",err.Error()) }
   return filepath.Join(home,CREDSFILE)
 }
 
@@ -263,7 +266,7 @@ func readcreds(path string) (credentials, bool, error) { // --------------------
 
   st,err:=os.Stat(path)
   if err!=nil { return c,false,err }
-  if (st.Mode().Perm()&0o077 != 0) { PE(path+" can be read by others",SF("chmod 600 %s",path)) }
+  if (st.Mode().Perm()&0o077 != 0 && !jsonmode()) { PE(path+" can be read by others",SF("chmod 600 %s",path)) }
 
   b,err:=os.ReadFile(path)
   if err!=nil { return c,false,err }

dns.go

@@ -42,6 +42,7 @@ var opt_y *bool
 func main() { // ========================================================================================== MAIN
 
   opt_y = flag.Bool("y",false,"")
+  opt_j = flag.Bool("j",false,"")
 
   opt_a := flag.String("a","","")                                                                // option setup
   opt_o := flag.String("o","","")
@@ -57,6 +58,8 @@ func main() { // ===============================================================
   opt_i := flag.String("i","","")
   opt_q := flag.String("q","","")
   opt_t := flag.String("t","","")
+  opt_M := flag.String("M","","")
+  opt_p := flag.Int("p",10,"")
   opt_h := flag.Bool("h", false, "")
   opt_v := flag.Bool("v", false, "")
 
@@ -83,11 +86,17 @@ func main() { // ===============================================================
     P(Cw("  -t <record name> -a <text>         add text record"))
     P(Cw("  -t <record name> -D                remove text record"))
     P(Cw("  -t <record name>                   show text record"))
+    P(Cw("  -M <domain> -a <server> [-p <n>]   add or change mx record, preference n (default 10)"))
+    P(Cw("  -M <domain> -d <server>            remove mx record"))
+    P(Cw("  -M <domain> -D                     remove all mx records"))
+    P(Cw("  -M <domain>                        show mx records"))
     P(Cw("  -r                                 restart infoblox grid"))
     P(Cw("  -l                                 list unused ip addresses"))
     P(Cw("  -c                                 run as certbot auth hook"))
     P(Cw("  -x                                 run as certbot cleanup hook"))
     P(Cw("  -y                                 supress interactive mode, alwayes answer 'yes'"))
+    P(Cw("  -j                                 answer with one line of json, for scripts"))
+    P(Cw("                                     (not --seal, --update, --check-update)"))
     P(Cw("  --seal                             encrypt an infoblox login into a block for creds.go"))
     P(Cw("  --check-update                     look for a newer release"))
     P(Cw("  --update                           download and install the newest release"))
@@ -97,6 +106,11 @@ func main() { // ===============================================================
   }
   flag.Parse()
 
+  // From here on an answer is a json object, the ones that end the run                   // json.go
+  // included — checkaccess, getcreds and findservice all reach the caller
+  // through Fatal.
+  if (*opt_j) { Fatal=jfatal }
+
   // These run before checkaccess, getcreds and findservice: none of them needs           // no service,
   // the infoblox service, a login or the right network. Sealing a login is done          // no login,
   // wherever it is convenient, and selfupdate.go probes a fresh download with            // no net check
@@ -105,7 +119,7 @@ func main() { // ===============================================================
   } else if  (*opt_update)              {  runupdate(selfUpdate.install); return
   } else if  (*opt_checkupdate)         {  runupdate(selfUpdate.check); return
   } else if  (*opt_seal)                {  sealcmd(); return
-  } else if  (*opt_v)                   {  info(); return
+  } else if  (*opt_v)                   {  showversion(); return
   } else if  (*opt_h)                   {  flag.Usage(); return
   }
 
@@ -125,69 +139,81 @@ func main() { // ===============================================================
   } else if  (*opt_t!="" && *opt_D)     {  deltxt(*opt_t) 
   } else if  (*opt_t!="" )              {  showtxt(*opt_t) 
 
+  } else if  (*opt_M!="" && *opt_a!="") {  addmx(*opt_M,*opt_a,*opt_p,Isflagpassed("p"))
+  } else if  (*opt_M!="" && *opt_d!="") {  delmx(*opt_M,*opt_d)
+  } else if  (*opt_M!="" && *opt_D)     {  delmx(*opt_M,"")
+  } else if  (*opt_M!="" )              {  showmx(*opt_M)
+
   } else if  (*opt_a!="")               {  addhost(*opt_a,*opt_i,*opt_m)  
   } else if  (*opt_d!="")               {  delhost(*opt_d) 
   } else if  (*opt_s!="")               {  showhost(*opt_s)  
   
   } else if  (*opt_o!="")               {  setoptions(*opt_o,*opt_i)  
   } else if  (*opt_f!="")               {  find(*opt_f)  
-  } else if  (*opt_i!="")               {  showip(*opt_i) 
-  } else if  (*opt_r)                   {  gridrestart()  
-  
-  } else if  (*opt_l)                   {  listunused() 
-  
+  } else if  (*opt_i!="")               {  showip(*opt_i)
+  } else if  (*opt_r)                   {  restart()
+
+  } else if  (*opt_l)                   {  listunused()
+
   } else if  (*opt_c)                   {  certbotauth()
   } else if  (*opt_x)                   {  certbotclean()
 
+  } else if  (*opt_j)                   {  fail("dns","no operation given")
   } else                                {  flag.Usage()
   }
 
   // Costs nothing: the hint comes from the note in the cache, and the asking
-  // happens once a day at most, in the background.
-  if hint:=selfUpdate.daily(); hint!="" { fmt.Fprintln(os.Stderr,Cy(hint)) }
+  // happens once a day at most, in the background. A json run is left alone
+  // with it: nobody there is going to update anything.
+  if (!*opt_j) {
+    if hint:=selfUpdate.daily(); hint!="" { fmt.Fprintln(os.Stderr,Cy(hint)) }
+  }
 }
 
 // ================================================================================================ HOST RECORDS
 
 func addhost(name string, ip string, mac string) { // ------------------------------------------ add host record
-  if (ip=="") { ip=nextip() }
-  
+  if (ip=="") {
+    ip=nextip()
+    if (ip=="") { fail("addhost","no free ip address available"); return }
+  }
+
   data:=`{"name":"`+hn(name)+`","ipv4addrs":[{"ipv4addr":"`+ip+`"}]}`
   if (len(mac)>0) { data=`{"name":"`+hn(name)+`","ipv4addrs":[{"ipv4addr":"`+ip+`","mac":"`+mac+`"}]}` }
-  
+
   body:=request("POST", URL+"record:host", data)
 
-  if gjson.Get(body, "Error").Exists() {
-    PE(gjson.Get(body, "Error").String())
-  } else {
-    if (mac!="") { 
-      gridrestart() 
-      PO("host '"+hn(name)+"' added with IP '"+ip+"' and MAC '"+mac+"'")
-    } else {
-      PO("host '"+hn(name)+"' added with IP '"+ip+"'")
-    }
-  } 
+  if gjson.Get(body, "Error").Exists() { fail("addhost",gjson.Get(body, "Error").String()); return }
+
+  // The restart is the grid's business, not the record's: it has been added
+  // either way, so a restart that goes wrong is a warning beside the answer
+  // and not an answer of its own.
+  warn:=""
+  msg:="host '"+hn(name)+"' added with IP '"+ip+"'"
+  if (mac!="") {
+    warn=gridrestart()
+    msg="host '"+hn(name)+"' added with IP '"+ip+"' and MAC '"+mac+"'"
+  }
+
+  done(answer{Action: "addhost", Name: hn(name), IP: ip, MAC: mac, Warning: warn},msg)
 }
 
 func delhost(name string) { // --------------------------------------------------------------- delete host record
   body:=request("GET", URL+"record:host?name="+hn(name),"")
-  
+
   gj := gjson.Parse(body).Array()
-  
-  if (len(gj)==1) {
-    fref := gjson.Get(body, "0._ref").String()
-    fname := gjson.Get(body, "0.name").String()
 
-    ans:=Yesno("remove host record '"+fname+"'",false,*opt_y);
+  if (len(gj)!=1) { fail("delhost","host record not found"); return }
 
-    if (ans) {
-      exedelete(fref)
-      PO("host '"+hn(name)+"' deleted")
-    }
-  } else {
-    PE("host record not found")
-  }
-} 
+  fref := gjson.Get(body, "0._ref").String()
+  fname := gjson.Get(body, "0.name").String()
+
+  if (!confirm("delhost","remove host record '"+fname+"'")) { return }
+
+  if e:=exedelete(fref); e!="" { fail("delhost",e); return }
+
+  done(answer{Action: "delhost", Name: hn(name)},"host '"+hn(name)+"' deleted")
+}
 
 func showhost(name string) { // --------------------------------------------------------------- show host record
   
@@ -200,17 +226,19 @@ func showhost(name string) { // ------------------------------------------------
   body:=request("GET", URL+"record:host?name="+hn(name)+"&_return_fields="+FIELDS, "")
       
   gj := gjson.Parse(body).Array()
-  
-  if (len(gj)==1) {
-    prettyjson(gj[0].String())
-  } else {
-    PE("host '"+hn(name)+"' not found")
-  }    
-} 
+
+  if (len(gj)!=1) { fail("showhost","host '"+hn(name)+"' not found"); return }
+
+  if (jsonmode()) {
+    done(answer{Action: "showhost", Name: hn(name), Record: json.RawMessage(gj[0].Raw)},"")
+    return
+  }
+  prettyjson(gj[0].String())
+}
 
 func find(name string) { // ------------------------------------------------------------------- find host record
   body:=request("GET", URL+"record:host?name~="+name, "")
-    
+
   max:=0
   gj := gjson.Parse(body).Array()
   for _, v := range gj {
@@ -218,6 +246,20 @@ func find(name string) { // ----------------------------------------------------
     if (len(name)>max) { max=len(name)}
   }
 
+  if (jsonmode()) {
+    hosts:=[]jhost{}
+    for _, v := range gj {
+      h:=jhost{Name: gjson.Get(v.String(), "name").String(), IPs: []jaddr{}}
+      for _, i := range gjson.Get(v.String(), "ipv4addrs").Array() {
+        h.IPs=append(h.IPs,jaddr{IP: gjson.Get(i.String(), "ipv4addr").String(),
+                                 MAC: gjson.Get(i.String(), "mac").String()})
+      }
+      hosts=append(hosts,h)
+    }
+    done(answer{Action: "find", Name: name, Hosts: &hosts, Count: ptr(len(hosts))},"")
+    return
+  }
+
   for _, v := range gj {
     name := gjson.Get(v.String(), "name").String()
     ips := gjson.Get(v.String(), "ipv4addrs").Array()
@@ -255,21 +297,28 @@ func showip (ip string) { // ---------------------------------------------------
   body:=request("GET", URL+"record:host_ipv4addr?ipv4addr="+ip+"&_return_fields%2B="+FIELDS, "")
       
   gj := gjson.Parse(body).Array()
-  
-  if (len(gj)==1) {
-    prettyjson(gj[0].String())
-  } else {
-    PE("host '"+ip+"' not found")
-  }      
-} 
+
+  if (len(gj)!=1) { fail("showip","host '"+ip+"' not found"); return }
+
+  if (jsonmode()) {
+    done(answer{Action: "showip", IP: ip, Record: json.RawMessage(gj[0].Raw)},"")
+    return
+  }
+  prettyjson(gj[0].String())
+}
 
 func listunused() { // ---------------------------------------------------------------- list unused ip addresses
   body:=request("GET", URL+"ipv4address?network="+CIDR+"&status=UNUSED", "")
   gj := gjson.Parse(body).Array()
-  for _, v := range gj {
-    ip := gjson.Get(v.String(), "ip_address").String()
-    P(ip)
+
+  ips:=[]string{}
+  for _, v := range gj { ips=append(ips,gjson.Get(v.String(), "ip_address").String()) }
+
+  if (jsonmode()) {
+    done(answer{Action: "listunused", IPs: &ips, Count: ptr(len(ips))},"")
+    return
   }
+  for _, ip := range ips { P(ip) }
 }
 
 func nextip() string { // -------------------------------------------------------------------- find next free IP
@@ -293,6 +342,12 @@ func getaliases(host string) []string { // -------------------------------------
 
 func showaliases(host string) { // ---------------------------------------------------------------- show aliases
   aliases:=getaliases(host)
+
+  if (jsonmode()) {
+    done(answer{Action: "showaliases", Name: hn(host), Aliases: &aliases, Count: ptr(len(aliases))},"")
+    return
+  }
+
   if (len(aliases)>0) {
     PF("%s '%s'\n",Cwb("Aliases for"),Cwb(hn(host)))
     for _, a := range aliases { PF("  %s\n",Cw(a)) }
@@ -303,11 +358,13 @@ func showaliases(host string) { // ---------------------------------------------
 
 
 func alias(mode int, host string, alias string) { // --------------------- alias (0=add, 1=delete, 2=delete all)
+  action:=[]string{"addalias","delalias","delaliases"}[mode]
+
   ref:=hostref(host)
 
   ans:=true
-  if (mode==1) { ans=Yesno("remove aliases '"+hn(alias)+"' from host record '"+hn(host)+"'",false,*opt_y) }
-  if (mode==2) { ans=Yesno("remove ALL aliases from host record '"+hn(host)+"'",false,*opt_y) }
+  if (mode==1) { ans=confirm(action,"remove aliases '"+hn(alias)+"' from host record '"+hn(host)+"'") }
+  if (mode==2) { ans=confirm(action,"remove ALL aliases from host record '"+hn(host)+"'") }
   if (!ans) { return }
 
   aliases:=getaliases(host)
@@ -325,19 +382,20 @@ func alias(mode int, host string, alias string) { // --------------------- alias
   data,_:=json.Marshal(map[string][]string{"aliases": aliases})
     
   body:=request("PUT",URL+ref,string(data))
-    
-  if gjson.Get(body,"Error").Exists() {
-    PE(gjson.Get(body,"Error").String())
-  } else {
-    if (mode==1) {
-      PO("alias '"+hn(alias)+"' removed from host record '"+hn(host)+"'")
-    } else if (mode==2) {
-      PO("all aliases removed from host record '"+hn(host)+"'")
-    } else {
-      PO("alias '"+hn(alias)+"' added to host '"+hn(host)+"'")
-    }
-  }
-         
+
+  if gjson.Get(body,"Error").Exists() { fail(action,gjson.Get(body,"Error").String()); return }
+
+  msg:="alias '"+hn(alias)+"' added to host '"+hn(host)+"'"
+  if (mode==1) { msg="alias '"+hn(alias)+"' removed from host record '"+hn(host)+"'" }
+  if (mode==2) { msg="all aliases removed from host record '"+hn(host)+"'" }
+
+  // 'aliases' is what the record carries now, which is the thing a script that
+  // just changed it wants to see. No alias is named when all of them went:
+  // hn("") would invent one out of the default domain.
+  a:=answer{Action: action, Name: hn(host), Aliases: &aliases, Count: ptr(len(aliases))}
+  if (alias!="") { a.Alias=hn(alias) }
+
+  done(a,msg)
 }
 
 
@@ -347,44 +405,194 @@ func alias(mode int, host string, alias string) { // --------------------- alias
 func addtxt(name string, txt string) { // ------------------------------------------------------- add txt record
   body:=request("POST",URL+"record:txt", `{"name":"`+name+`","text":"`+txt+`"}`)
 
-  if gjson.Get(body, "Error").Exists() {
-    PE(gjson.Get(body, "Error").String())
-  } else {
-    PO("txt record '"+name+"' added with txt '"+txt+"'")
-  } 
+  if gjson.Get(body, "Error").Exists() { fail("addtxt",gjson.Get(body, "Error").String()); return }
+
+  done(answer{Action: "addtxt", Name: name, Text: txt},"txt record '"+name+"' added with txt '"+txt+"'")
 }
 
 func deltxt(name string) { // ---------------------------------------------------------------- delete txt record
   refs:=txtrefs(name)
-  n:=len(refs)
-  if (n>0) {
-    ans:=Yesno("remove txt record '"+name+"'",false,*opt_y);
-    if (ans) {
-      for _, ref := range refs {
-        exedelete(ref)
-      }
-    }
-  } else {
-    PE("txt record not found")
-    return
+
+  if (len(refs)==0) { fail("deltxt","txt record not found"); return }
+
+  if (!confirm("deltxt","remove txt record '"+name+"'")) { return }
+
+  // Every one of them is tried before anything is said about it: a name can
+  // carry several records, and one that will not go is no reason to leave the
+  // rest standing.
+  bad:=""
+  for _, ref := range refs {
+    if e:=exedelete(ref); e!="" && bad=="" { bad=e }
   }
+  if (bad!="") { fail("deltxt",bad); return }
+
+  done(answer{Action: "deltxt", Name: name, Count: ptr(len(refs))},"")     // has never said anything, still does not
 }
 
 func showtxt(name string) { // ----------------------------------------------------------------- show txt record
   data:=request("GET", URL+"record:txt?name="+hn(name), "")
-  
+
   gj:=gjson.Parse(data).Array()
   n:=len(gj)
-  
-  if (n>0) {
-    PF("%s '%s'\n",Cwb("Txt records for"),Cwb(name))
-    for i := 0; i < n; i++ {
-      PF("  %s\n",Cw(gj[i].Get("text")))
-    }
-  } else {
-    PE("txt record '"+hn(name)+"' not found")
+
+  if (n==0) { fail("showtxt","txt record '"+hn(name)+"' not found"); return }
+
+  texts:=[]string{}
+  for i := 0; i < n; i++ { texts=append(texts,gj[i].Get("text").String()) }
+
+  if (jsonmode()) {
+    done(answer{Action: "showtxt", Name: hn(name), Texts: &texts, Count: ptr(n)},"")
+    return
   }
-  
+
+  PF("%s '%s'\n",Cwb("Txt records for"),Cwb(name))
+  for _, t := range texts { PF("  %s\n",Cw(t)) }
+}
+
+
+
+// ================================================================================================== MX RECORDS
+//
+// The name of an mx record is the domain the mail is addressed to, not a host:
+// 'dns -M fhi.mpg.de -a mail1 -p 10' says that mail for fhi.mpg.de goes to
+// mail1.fhi.mpg.de, and the preference decides in which order several of them
+// are tried, lowest first.
+//
+// A domain carries one record per mail server, so the server is what a single
+// record is addressed by: -a puts one in or moves it to another preference, -d
+// takes that one out, -D takes all of them out.
+
+type mxrec struct { // ------------------------------------------------------------------ one mx record, as read
+  ref  string
+  mx   string
+  pref int
+}
+
+func getmx(name string) []mxrec { // -------------------------------------------- get the mx records of a domain
+  body:=request("GET", URL+"record:mx?name="+hn(name)+"&_return_fields=mail_exchanger,preference", "")
+
+  recs:=[]mxrec{}
+  for _, v := range gjson.Parse(body).Array() {
+    recs=append(recs,mxrec{ref:  v.Get("_ref").String(),
+                           mx:   v.Get("mail_exchanger").String(),
+                           pref: int(v.Get("preference").Int())})
+  }
+
+  // Lowest preference first, the order the mail servers are tried in. An equal
+  // pair is settled by the name, so that two runs read the same.
+  slices.SortFunc(recs, func(a mxrec, b mxrec) int {
+    if (a.pref!=b.pref) { return a.pref-b.pref }
+    return strings.Compare(a.mx,b.mx)
+  })
+
+  return recs
+}
+
+func jmxs(recs []mxrec) []jmx { // -------------------------------------------- the same list, for a json answer
+  l:=[]jmx{}
+  for _, r := range recs { l=append(l,jmx{MX: r.mx, Pref: r.pref}) }
+  return l
+}
+
+func showmx(name string) { // ------------------------------------------------------------------ show mx records
+  recs:=getmx(name)
+
+  // A domain without mail is an ordinary state and not a failure, so this one
+  // answers the empty list rather than an error, the way the aliases do.
+  if (jsonmode()) {
+    l:=jmxs(recs)
+    done(answer{Action: "showmx", Name: hn(name), MXs: &l, Count: ptr(len(l))},"")
+    return
+  }
+
+  if (len(recs)==0) {
+    PF("%s '%s'\n",Cwb("No mx records found for"),Cwb(hn(name)))
+    return
+  }
+
+  PF("%s '%s'\n",Cwb("Mx records for"),Cwb(hn(name)))
+  for _, r := range recs { PF("  %s  %s\n",Cw(SF("%5d",r.pref)),Cw(r.mx)) }
+}
+
+func addmx(name string, mx string, pref int, given bool) { // ----------------------- add or change an mx record
+  if (given && (pref<0 || pref>65535)) { fail("addmx","preference has to be between 0 and 65535"); return }
+
+  // The mail server is what the record is addressed by, so one that is already
+  // there is changed instead of added a second time: infoblox would take the
+  // second one — same domain, same server, another preference — and the domain
+  // would end up with two records where one was meant.
+  old:=[]mxrec{}
+  for _, r := range getmx(name) { if (r.mx==hn(mx)) { old=append(old,r) } }
+
+  if (len(old)>1) {
+    fail("addmx","'"+hn(mx)+"' is on '"+hn(name)+"' more than once, remove it first with -d")
+    return
+  }
+
+  if (len(old)==1) {
+    // Without -p there is nothing to change: the preference on the record is
+    // the one that was asked for, not the default of the option.
+    if (!given || old[0].pref==pref) {
+      done(answer{Action: "changemx", Name: hn(name), MX: hn(mx), Pref: ptr(old[0].pref)},
+        "mx record '"+hn(mx)+"' on '"+hn(name)+"' unchanged, preference "+Itoa(old[0].pref))
+      return
+    }
+
+    body:=request("PUT", URL+old[0].ref, `{"preference":`+Itoa(pref)+`}`)
+
+    if gjson.Get(body,"Error").Exists() { fail("changemx",gjson.Get(body,"Error").String()); return }
+
+    done(answer{Action: "changemx", Name: hn(name), MX: hn(mx), Pref: ptr(pref)},
+      "mx record '"+hn(mx)+"' on '"+hn(name)+"' changed from preference "+Itoa(old[0].pref)+
+      " to "+Itoa(pref))
+    return
+  }
+
+  data:=`{"name":"`+hn(name)+`","mail_exchanger":"`+hn(mx)+`","preference":`+Itoa(pref)+`}`
+
+  body:=request("POST", URL+"record:mx", data)
+
+  if gjson.Get(body,"Error").Exists() { fail("addmx",gjson.Get(body,"Error").String()); return }
+
+  done(answer{Action: "addmx", Name: hn(name), MX: hn(mx), Pref: ptr(pref)},
+    "mx record '"+hn(mx)+"' added to '"+hn(name)+"' with preference "+Itoa(pref))
+}
+
+func delmx(name string, mx string) { // --------------------------------- delete mx records ("" for all of them)
+  action:="delmx"
+  if (mx=="") { action="delmxs" }
+
+  gone:=[]mxrec{}
+  for _, r := range getmx(name) { if (mx=="" || r.mx==hn(mx)) { gone=append(gone,r) } }
+
+  if (len(gone)==0) {
+    if (mx=="") { fail(action,"no mx records found for '"+hn(name)+"'"); return }
+    fail(action,"mx record '"+hn(mx)+"' not found on '"+hn(name)+"'")
+    return
+  }
+
+  ask:="remove mx record '"+hn(mx)+"' from '"+hn(name)+"'"
+  if (mx=="") { ask="remove ALL mx records from '"+hn(name)+"'" }
+  if (!confirm(action,ask)) { return }
+
+  // As with the txt records, every one of them is tried before anything is
+  // said about it: one that will not go is no reason to leave the rest
+  // standing.
+  bad:=""
+  for _, r := range gone {
+    if e:=exedelete(r.ref); e!="" && bad=="" { bad=e }
+  }
+  if (bad!="") { fail(action,bad); return }
+
+  msg:="mx record '"+hn(mx)+"' removed from '"+hn(name)+"'"
+  if (mx=="") { msg="all mx records removed from '"+hn(name)+"'" }
+
+  // No server is named when all of them went: hn("") would invent one out of
+  // the default domain.
+  a:=answer{Action: action, Name: hn(name), Count: ptr(len(gone))}
+  if (mx!="") { a.MX=hn(mx) }
+
+  done(a,msg)
 }
 
 
@@ -396,42 +604,44 @@ func certbotauth() { // --------------------------------------------------------
   validation := os.Getenv("CERTBOT_VALIDATION")
 
   if domain == "" || validation == "" {
-    PE("Error: CERTBOT_DOMAIN or CERTBOT_VALIDATION environment variables missing")
-    os.Exit(1)
+    fail("certbotauth","CERTBOT_DOMAIN or CERTBOT_VALIDATION environment variables missing")
+    os.Exit(1)                                          // fail ends a json run by itself, this one ends the other
   }
 
   name := "_acme-challenge." + domain
   body := request("POST", URL+"record:txt", `{"name":"`+name+`","text":"`+validation+`"}`)
 
   if gjson.Get(body, "Error").Exists() {
-    PE(gjson.Get(body, "Error").String())
-    os.Exit(1) 
-  } else {
-    PO("Certbot auth: TXT record '" + name + "' added")
-    time.Sleep(10 * time.Second) 
+    fail("certbotauth",gjson.Get(body, "Error").String())
+    os.Exit(1)
   }
+
+  done(answer{Action: "certbotauth", Name: name, Text: validation},"Certbot auth: TXT record '"+name+"' added")
+  time.Sleep(10 * time.Second)
 }
 
 func certbotclean() { // ------------------------------------------------------------------ certbot cleanup hook
   domain := os.Getenv("CERTBOT_DOMAIN")
 
   if domain == "" {
-    PE("Error: CERTBOT_DOMAIN environment variable missing")
-    os.Exit(1)
+    fail("certbotclean","CERTBOT_DOMAIN environment variable missing")
+    os.Exit(1)                                          // fail ends a json run by itself, this one ends the other
   }
 
   name := "_acme-challenge." + domain
   refs := txtrefs(name)
 
   n := len(refs)
-  if n > 0 {
-    for _, ref := range refs {
-      exedelete(ref)
-    }
-    PO("certbot cleanup: " + SF("%d", n) + " txt record(s) for '" + name + "' removed")
-  } else {
-    PO("certbot cleanup: no txt records found for '" + name + "' to delete")
+  bad:=""
+  for _, ref := range refs {
+    if e:=exedelete(ref); e!="" && bad=="" { bad=e }          // all of them go, whatever one of them has to say
   }
+  if (bad!="") { fail("certbotclean",bad); return }
+
+  msg:="certbot cleanup: no txt records found for '" + name + "' to delete"
+  if (n>0) { msg="certbot cleanup: " + SF("%d", n) + " txt record(s) for '" + name + "' removed" }
+
+  done(answer{Action: "certbotclean", Name: name, Count: ptr(n)},msg)
 }
 
 
@@ -440,37 +650,49 @@ func certbotclean() { // -------------------------------------------------------
 
 func setoptions(file string, ip string) { // ------------------------------------------------- set options to ip
   ref:=ipref(ip)
-  
-  filecontent,_ := os.ReadFile(file)
-  
+
+  // Unread until now: an unreadable file went to infoblox as an empty body and
+  // took whatever was on the record with it.
+  filecontent,err := os.ReadFile(file)
+  if err!=nil { fail("setoptions","cannot read "+file,err.Error()); return }
+
   body:=request("PUT",URL+ref, string(filecontent))
 
-  if gjson.Get(body, "Error").Exists() {
-    PE(gjson.Get(body, "Error").String())
-  } else {
-    gridrestart() 
-    PO("options added to ip '"+ip+"'")
-  } 
+  if gjson.Get(body, "Error").Exists() { fail("setoptions",gjson.Get(body, "Error").String()); return }
+
+  warn:=gridrestart()
+
+  done(answer{Action: "setoptions", IP: ip, File: file, Warning: warn},"options added to ip '"+ip+"'")
 }
 
 func runupdate(task func(io.Writer) error) { // ----------------------------------- run a task from selfupdate.go
   if err:=task(os.Stdout); err!=nil { PE(err.Error()); os.Exit(1) }
 }
 
-func gridrestart() { // ----------------------------------------------------------------------- restart infoblox
+// Both of these are steps inside other operations as much as operations in
+// their own right, so they say nothing themselves: they hand back what went
+// wrong, empty when nothing did, and whoever called decides whether that is
+// the answer or a remark beside it.
+
+func gridrestart() string { // ----------------------------------------------------------------- restart infoblox
   ref:=gridref()
 
   body:=request("POST", URL+ref+"?_function=restartservices",
     `{"restart_option":"RESTART_IF_NEEDED","service_option":"ALL",`+
     `"member_order":"SEQUENTIALLY", "sequential_delay":1}`)
 
-  if gjson.Get(string(body), "Error").Exists() { PE(gjson.Get(string(body), "Error").String()) } 
+  return gjson.Get(string(body), "Error").String()
 }
 
-func exedelete(ref string) { // ------------------------------------------------------------ delete by reference
+func restart() { // ----------------------------------------------------------------------- -r: restart the grid
+  if e:=gridrestart(); e!="" { fail("gridrestart",e); return }
+  done(answer{Action: "gridrestart"},"")                                  // has never said anything, still does not
+}
+
+func exedelete(ref string) string { // ----------------------------------------------------- delete by reference
   body:=request("DELETE", URL+ref, "")
-  if gjson.Get(body, "Error").Exists() { PE(gjson.Get(body, "Error").String()) } 
-} 
+  return gjson.Get(body, "Error").String()
+}
 
 
 
@@ -517,23 +739,30 @@ func request(method string, url string, data string) (string) { // -------------
   if data != "" { bdata = bytes.NewReader([]byte(data)) }
   
   req, err := http.NewRequest(method,url,bdata)
-  if err != nil { PE(err.Error()); os.Exit(1) }  
-    
+  if err != nil { Fatal(err.Error()) }
+
   req.SetBasicAuth(US,PW)
   req.Header.Set("Content-Type","application/json")
-  
+
   resp,err:=client.Do(req)
-  if err != nil { PE(err.Error()); os.Exit(1) }
-      
+  if err != nil { Fatal(err.Error()) }
+
   defer resp.Body.Close()
-  
-  if resp.StatusCode < 200 || resp.StatusCode >= 300 {
-    PE(SF("Unexpected http status code: %d",resp.StatusCode))
-  }
-  
+
   body, err := io.ReadAll(resp.Body)
-  if err != nil { PE(err.Error()); os.Exit(1) }
-  
+  if err != nil { Fatal(err.Error()) }
+
+  // The body is read first now: infoblox says what it did not like in there,
+  // and that is the better message of the two. A json run that gets neither a
+  // good status nor an explanation has nothing left to report and stops.
+  if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+    if (!jsonmode()) {
+      PE(SF("Unexpected http status code: %d",resp.StatusCode))
+    } else if (!gjson.Get(string(body), "Error").Exists()) {
+      Fatal(SF("unexpected http status code: %d",resp.StatusCode))
+    }
+  }
+
   return string(body)
 }
 
@@ -571,11 +800,16 @@ func findservice() { // --------------------------------------------------------
   }
   
   if (URL=="") {
+    why:=[]string{}
+    for i,url := range URLS { why=append(why,SF("%s: %s",url,MSG[i])) }
+
+    if (jsonmode()) { Fatal("no working service found",strings.Join(why,"; ")) }
+
     PE("No working service found")
-    for i,url := range URLS { PE(SF("%s: %s",url,MSG[i])) }
+    for _, w := range why { PE(w) }
     os.Exit(1)
   }
-} 
+}
 
 func prettyjson(str string) { // ------------------------------------------------------------------- format json
   var prettyJSON bytes.Buffer

json.go

@@ -0,0 +1,141 @@
+// =========================================================================== machine readable answers (mwx'2026)
+//
+// -j puts one json object on stdout and nothing else: no colours, no sentences,
+// no questions. A script reads the object, looks at "ok" and takes the fields
+// it needs; whoever only looks at the exit status finds the same answer there,
+// 0 or 1.
+//
+// One run, one object. The operations that otherwise print line after line say
+// the same thing in a list, and everything that can go wrong before the answer
+// — the network check, the login, the service, infoblox itself — comes back in
+// that same shape. That is what Fatal is redirected for.
+//
+// A question cannot be answered by a script, so -j never asks one: -y is the
+// answer, and an operation that would have asked and did not get it says so
+// rather than going ahead.
+//
+// --seal, --update and --check-update keep their prose. They are maintenance
+// done by hand, and nobody is parsing them.
+package main
+
+import (
+	"encoding/json"
+	"os"
+)
+
+var opt_j *bool
+
+// One struct for all of them rather than one apiece: an operation fills in what
+// it has to say and omitempty keeps the rest out of the answer. The lists and
+// the count are pointers so that 'none at all' can still be written as an empty
+// list or a nought — a script should not have to tell a missing key from one
+// that is genuinely empty.
+type answer struct {
+  OK      bool            `json:"ok"`
+  Action  string          `json:"action"`
+  Error   string          `json:"error,omitempty"`
+  Detail  string          `json:"detail,omitempty"`
+  Warning string          `json:"warning,omitempty"`
+
+  Name    string          `json:"name,omitempty"`
+  IP      string          `json:"ip,omitempty"`
+  MAC     string          `json:"mac,omitempty"`
+  Alias   string          `json:"alias,omitempty"`
+  Text    string          `json:"text,omitempty"`
+  File    string          `json:"file,omitempty"`
+  MX      string          `json:"mx,omitempty"`
+
+  // A preference of 0 is a preference like any other, so this one is a pointer
+  // too: omitempty would drop it and the answer would read as if the record had
+  // none.
+  Pref    *int            `json:"preference,omitempty"`
+
+  Aliases *[]string       `json:"aliases,omitempty"`
+  Texts   *[]string       `json:"texts,omitempty"`
+  IPs     *[]string       `json:"ips,omitempty"`
+  Hosts   *[]jhost        `json:"hosts,omitempty"`
+  MXs     *[]jmx          `json:"mxs,omitempty"`
+  Record  json.RawMessage `json:"record,omitempty"`
+  Count   *int            `json:"count,omitempty"`
+
+  Version string          `json:"version,omitempty"`
+  Build   string          `json:"build,omitempty"`
+  Toolbox string          `json:"toolbox,omitempty"`
+}
+
+type jhost struct { // ------------------------------------------------------------------ one hit of a host search
+  Name string  `json:"name"`
+  IPs  []jaddr `json:"ips"`
+}
+
+type jaddr struct { // ------------------------------------------------------------------ one address of such a hit
+  IP  string `json:"ip"`
+  MAC string `json:"mac,omitempty"`
+}
+
+type jmx struct { // ------------------------------------------------------------------- one mx record of a domain
+  MX   string `json:"mx"`
+  Pref int    `json:"preference"`
+}
+
+func jsonmode() bool { return opt_j!=nil && *opt_j } // ------------------------------- is this a run for a machine
+
+func ptr[T any](v T) *T { return &v } // ----------------------------- something present, even when it is empty
+
+
+
+// ==================================================================================================== ANSWERING
+
+func done(a answer, msg string) { // ----------------------------------- an operation that did what it was asked
+  a.OK=true
+  if (jsonmode()) { jprint(a); return }
+
+  if (a.Warning!="") { PE(a.Warning) }
+  if (msg!="")       { PO(msg) }                  // no sentence: the operations that never had one keep quiet
+}
+
+// Not the end of the run in the ordinary mode — saying so and carrying on is
+// what dns has always done, and what has been built around it lives off the
+// exit status it gets today. A json run does end here, with 1: a script must
+// not have to tell an empty answer from a failed one.
+func fail(action string, msg ...string) {
+  if (jsonmode()) {
+    jprint(failed(action,msg))
+    os.Exit(1)
+  }
+  PE(msg...)
+}
+
+func jfatal(msg ...string) { // ------------------------------- what Fatal does in a json run: the object, and out
+  jprint(failed("dns",msg))
+  os.Exit(1)
+}
+
+func failed(action string, msg []string) answer { // ----------------------------- message and detail, as PE takes them
+  a:=answer{Action: action, Error: msg[0]}
+  if (len(msg)>1) { a.Detail=msg[1] }
+  return a
+}
+
+func jprint(a answer) { // -------------------------------------------------------------------- the object, one line
+  b,err:=json.Marshal(a)
+  if err!=nil { PE(err.Error()); os.Exit(1) }
+  P(string(b))
+}
+
+// The one place a run can still stop and wait. In json mode -y stands in for
+// the answer, and without it the operation does not happen: doing it anyway
+// unasked is not a decision this program gets to make for the caller.
+func confirm(action string, msg string) bool {
+  if (!jsonmode()) { return Yesno(msg,false,*opt_y) }
+  if (*opt_y)      { return true }
+  fail(action,"confirmation required, add -y")
+  return false
+}
+
+func showversion() { // ------------------------------------------------------------------------ -v, either way
+  if (!jsonmode()) { info(); return }
+  done(answer{Action: "version", Version: version, Build: build, Toolbox: tbversion},"")
+}
+
+// ========================================================================================================== END

json_test.go

@@ -0,0 +1,285 @@
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+	"os/exec"
+	"slices"
+	"strings"
+	"testing"
+)
+
+// Runs f with stdout on a pipe and hands back what it wrote. P, PO and PE all
+// reach for os.Stdout when they are called, so swapping it here is enough.
+func capture(t *testing.T, f func()) string {
+	t.Helper()
+
+	old := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	os.Stdout = w
+	f()
+	w.Close()
+	os.Stdout = old
+
+	b, err := io.ReadAll(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(b)
+}
+
+func asjson(t *testing.T, f func()) map[string]any {
+	t.Helper()
+
+	old := opt_j
+	opt_j = ptr(true)
+	out := capture(t, f)
+	opt_j = old
+
+	if n := strings.Count(strings.TrimSpace(out), "\n"); n != 0 {
+		t.Fatalf("one run has to say one line, said %d:\n%s", n+1, out)
+	}
+	var m map[string]any
+	if err := json.Unmarshal([]byte(out), &m); err != nil {
+		t.Fatalf("not json: %v\n%s", err, out)
+	}
+	return m
+}
+
+func TestAnswerIsOneObject(t *testing.T) {
+	m := asjson(t, func() {
+		done(answer{Action: "addhost", Name: "host.fhi.mpg.de", IP: "141.14.128.5"}, "host added")
+	})
+
+	if m["ok"] != true || m["action"] != "addhost" {
+		t.Errorf("ok/action wrong: %+v", m)
+	}
+	if m["name"] != "host.fhi.mpg.de" || m["ip"] != "141.14.128.5" {
+		t.Errorf("payload wrong: %+v", m)
+	}
+
+	// The sentence belongs to the other mode, and what was never filled in has
+	// no business in the answer.
+	for _, k := range []string{"mac", "error", "warning", "count", "aliases"} {
+		if _, there := m[k]; there {
+			t.Errorf("%q should not be in the answer: %+v", k, m)
+		}
+	}
+	if strings.Contains(strings.ToLower(m["action"].(string)), "host added") {
+		t.Error("the sentence leaked into the json")
+	}
+}
+
+// Nothing found is an answer too: an empty list must not turn into a missing
+// key, or a script cannot tell 'none' from 'this operation does not say'.
+func TestEmptyListStaysAList(t *testing.T) {
+	m := asjson(t, func() {
+		done(answer{Action: "showaliases", Name: "host", Aliases: ptr([]string{}), Count: ptr(0)}, "")
+	})
+
+	al, there := m["aliases"]
+	if !there {
+		t.Fatalf("aliases missing: %+v", m)
+	}
+	if l, isl := al.([]any); !isl || len(l) != 0 {
+		t.Errorf("aliases is %#v, want []", al)
+	}
+	if c, there := m["count"]; !there || c.(float64) != 0 {
+		t.Errorf("count is %#v, want 0", m["count"])
+	}
+}
+
+// The infoblox record goes in as a record, not as a string holding one.
+func TestRecordNestsAsAnObject(t *testing.T) {
+	m := asjson(t, func() {
+		done(answer{Action: "showhost", Record: json.RawMessage(`{"name":"a","ttl":300}`)}, "")
+	})
+
+	rec, isobj := m["record"].(map[string]any)
+	if !isobj {
+		t.Fatalf("record is %#v, want an object", m["record"])
+	}
+	if rec["name"] != "a" || rec["ttl"].(float64) != 300 {
+		t.Errorf("record wrong: %+v", rec)
+	}
+}
+
+func TestFailedCarriesMessageAndDetail(t *testing.T) {
+	a := failed("delhost", []string{"host record not found"})
+	if a.OK || a.Action != "delhost" || a.Error != "host record not found" || a.Detail != "" {
+		t.Errorf("got %+v", a)
+	}
+
+	a = failed("dns", []string{"no working service found", "ddi1: down; ddi2: down"})
+	if a.Detail != "ddi1: down; ddi2: down" {
+		t.Errorf("detail lost: %+v", a)
+	}
+}
+
+// A warning is what the answer carries when the record went in but the grid
+// restart did not: still ok, and still said.
+func TestWarningRidesAlong(t *testing.T) {
+	m := asjson(t, func() {
+		done(answer{Action: "addhost", Name: "h", IP: "1.2.3.4", MAC: "aa:bb", Warning: "grid busy"}, "added")
+	})
+	if m["ok"] != true || m["warning"] != "grid busy" {
+		t.Errorf("got %+v", m)
+	}
+}
+
+// The ordinary run keeps its sentences, and says the warning before them, the
+// way it always has.
+func TestHumanModeStillTalks(t *testing.T) {
+	old := opt_j
+	opt_j = ptr(false)
+	out := capture(t, func() {
+		done(answer{Action: "addhost", Name: "h", Warning: "grid busy"}, "host 'h' added")
+	})
+	opt_j = old
+
+	if !strings.Contains(out, "host 'h' added") {
+		t.Errorf("the sentence is gone: %q", out)
+	}
+	if !strings.Contains(out, "grid busy") {
+		t.Errorf("the warning is gone: %q", out)
+	}
+	if strings.Contains(out, `"ok"`) {
+		t.Errorf("json leaked into the ordinary run: %q", out)
+	}
+	if strings.Index(out, "grid busy") > strings.Index(out, "host 'h' added") {
+		t.Error("the warning has to come before the sentence")
+	}
+
+	// An operation that never had a sentence keeps quiet.
+	opt_j = ptr(false)
+	out = capture(t, func() { done(answer{Action: "gridrestart"}, "") })
+	opt_j = old
+	if out != "" {
+		t.Errorf("said %q, should have said nothing", out)
+	}
+}
+
+// -y is the answer in a json run. Without it the caller gets told, and the
+// operation does not happen — that path ends the run, so it is not exercised
+// here; this is the half that has to go through.
+func TestConfirmTakesY(t *testing.T) {
+	oldj, oldy := opt_j, opt_y
+	opt_j, opt_y = ptr(true), ptr(true)
+	defer func() { opt_j, opt_y = oldj, oldy }()
+
+	if out := capture(t, func() {
+		if !confirm("delhost", "remove host record 'h'") {
+			t.Error("-y was not taken as the answer")
+		}
+	}); out != "" {
+		t.Errorf("a json run must not ask anything: %q", out)
+	}
+}
+
+func TestVersionAnswers(t *testing.T) {
+	m := asjson(t, showversion)
+	if m["ok"] != true || m["action"] != "version" || m["version"] != version {
+		t.Errorf("got %+v", m)
+	}
+	if m["build"] != build || m["toolbox"] != tbversion {
+		t.Errorf("build/toolbox wrong: %+v", m)
+	}
+}
+
+// The other half of confirm ends the run, so it needs a run of its own. This is
+// the one that must not go wrong: a json call that would have asked, and got no
+// -y, has to come back with a refusal and delete nothing.
+func TestConfirmWithoutYStopsTheRun(t *testing.T) {
+	if os.Getenv("DNS_TEST_CONFIRM") == "1" {
+		opt_j, opt_y = ptr(true), ptr(false)
+		confirm("delhost", "remove host record 'h'")
+		os.Stdout.WriteString("CARRIED ON\n") // must never be reached
+		return
+	}
+
+	cmd := exec.Command(os.Args[0], "-test.run=TestConfirmWithoutYStopsTheRun")
+	cmd.Env = append(os.Environ(), "DNS_TEST_CONFIRM=1")
+	out, err := cmd.Output()
+
+	if strings.Contains(string(out), "CARRIED ON") {
+		t.Fatal("a json run went past a question it could not ask")
+	}
+	var code int
+	if ee, is := err.(*exec.ExitError); is {
+		code = ee.ExitCode()
+	}
+	if code != 1 {
+		t.Errorf("exit %d, want 1 (err %v, out %q)", code, err, out)
+	}
+
+	var m map[string]any
+	line := strings.SplitN(strings.TrimSpace(string(out)), "\n", 2)[0]
+	if err := json.Unmarshal([]byte(line), &m); err != nil {
+		t.Fatalf("no json answer: %v\n%s", err, out)
+	}
+	if m["ok"] != false || m["action"] != "delhost" {
+		t.Errorf("got %+v", m)
+	}
+	if e, _ := m["error"].(string); !strings.Contains(e, "-y") {
+		t.Errorf("the refusal has to name -y: %q", e)
+	}
+}
+
+// Preference 0 is a preference like any other — the answer has to carry it, and
+// the list of exchangers has to stay a list when a domain has none.
+func TestMXAnswerKeepsPreferenceZero(t *testing.T) {
+	m := asjson(t, func() {
+		done(answer{Action: "addmx", Name: "fhi.mpg.de", MX: "mail1.fhi.mpg.de", Pref: ptr(0)}, "added")
+	})
+
+	p, there := m["preference"]
+	if !there {
+		t.Fatalf("preference missing: %+v", m)
+	}
+	if p.(float64) != 0 {
+		t.Errorf("preference is %#v, want 0", p)
+	}
+	if m["mx"] != "mail1.fhi.mpg.de" || m["action"] != "addmx" {
+		t.Errorf("got %+v", m)
+	}
+
+	m = asjson(t, func() {
+		done(answer{Action: "showmx", Name: "fhi.mpg.de", MXs: ptr([]jmx{}), Count: ptr(0)}, "")
+	})
+	if l, isl := m["mxs"].([]any); !isl || len(l) != 0 {
+		t.Errorf("mxs is %#v, want []", m["mxs"])
+	}
+
+	// And a run that never touched an mx record must not mention one.
+	m = asjson(t, func() { done(answer{Action: "addhost", Name: "h", IP: "1.2.3.4"}, "added") })
+	for _, k := range []string{"mx", "mxs", "preference"} {
+		if _, there := m[k]; there {
+			t.Errorf("%q should not be in the answer: %+v", k, m)
+		}
+	}
+}
+
+// The order the mail servers are tried in is the answer's order: lowest
+// preference first, equal ones by name.
+func TestMXListIsSortedByPreference(t *testing.T) {
+	recs := []mxrec{{mx: "b.fhi.mpg.de", pref: 20}, {mx: "c.fhi.mpg.de", pref: 10},
+		{mx: "a.fhi.mpg.de", pref: 20}}
+
+	slices.SortFunc(recs, func(a mxrec, b mxrec) int {
+		if a.pref != b.pref {
+			return a.pref - b.pref
+		}
+		return strings.Compare(a.mx, b.mx)
+	})
+
+	want := []jmx{{MX: "c.fhi.mpg.de", Pref: 10}, {MX: "a.fhi.mpg.de", Pref: 20},
+		{MX: "b.fhi.mpg.de", Pref: 20}}
+
+	if got := jmxs(recs); !slices.Equal(got, want) {
+		t.Errorf("got %+v, want %+v", got, want)
+	}
+}

tools.go

@@ -33,11 +33,17 @@ var LR = []rune("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
 // Updating oneself lives in selfupdate.go — one file per program, configured at
 // its head, driven by the --update and --check-update options.
 
+// What the end of a run that cannot go on looks like. The default says it and
+// stops; a program that answers in something other than prose — dns -j — puts
+// its own here before anything can fail. Whatever is put here has to stop the
+// run: nothing that calls Fatal expects to get control back.
+var Fatal func(msg ...string) = func(msg ...string) { PE(msg...); os.Exit(1) }
+
 func checkaccess(NETS []string) { // ------------------------------------------------- check ip net based access
 	match:=0;
 	for _, validnet := range NETS {
 		addrs, err := net.InterfaceAddrs()
-		if err != nil { PE("Error getting addresses"); os.Exit(1) }
+		if err != nil { Fatal("Error getting addresses") }
 		_, ipNet, err := net.ParseCIDR(validnet)
 		for _, address := range addrs {
 			if ipnet, ok := address.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
@@ -48,7 +54,7 @@ func checkaccess(NETS []string) { // -------------------------------------------
 		}
 	}
 	
-	if (match==0) { PE("access violation, permission denied"); os.Exit(1) }
+	if (match==0) { Fatal("access violation, permission denied") }
 }
 
 

version.txt

@@ -1 +1 @@
-2.4.4
+2.5.1