From e1f01f0c8ac41c1604c19512b92ce1f19c416059 Mon Sep 17 00:00:00 2001
From: Evgeniy Khramtsov <ekhramtsov@process-one.net>
Date: Fri, 24 Mar 2017 11:03:23 +0300
Subject: [PATCH] Avoid PID collisions

Fixes #1470
---
 src/ejabberd_sm_sql.erl | 70 +++++++++++++++++++++++++++++++++--------
 1 file changed, 57 insertions(+), 13 deletions(-)

diff --git a/src/ejabberd_sm_sql.erl b/src/ejabberd_sm_sql.erl
index d59c3670a..9fc027588 100644
--- a/src/ejabberd_sm_sql.erl
+++ b/src/ejabberd_sm_sql.erl
@@ -47,7 +47,7 @@
 %%%===================================================================
 -spec init() -> ok | {error, any()}.
 init() ->
-    Node = jlib:atom_to_binary(node()),
+    Node = erlang:atom_to_binary(node(), latin1),
     ?INFO_MSG("Cleaning SQL SM table...", []),
     lists:foldl(
       fun(Host, ok) ->
@@ -68,8 +68,8 @@ set_session(#session{sid = {Now, Pid}, usr = {U, LServer, R},
     InfoS = jlib:term_to_expr(Info),
     PrioS = enc_priority(Priority),
     TS = now_to_timestamp(Now),
-    PidS = list_to_binary(erlang:pid_to_list(Pid)),
-    Node = jlib:atom_to_binary(node(Pid)),
+    PidS = enc_pid(Pid),
+    Node = erlang:atom_to_binary(node(Pid), latin1),
     case ?SQL_UPSERT(LServer, "sm",
                      ["!usec=%(TS)d",
                       "!pid=%(PidS)s",
@@ -89,7 +89,7 @@ delete_session(_LUser, LServer, _LResource, {Now, Pid}) ->
     PidS = list_to_binary(erlang:pid_to_list(Pid)),
     case ejabberd_sql:sql_query(
 	   LServer,
-	   ?SQL("select @(usec)d, @(pid)s, @(username)s,"
+	   ?SQL("select @(usec)d, @(pid)s, @(node)s, @(username)s,"
                 " @(resource)s, @(priority)s, @(info)s "
                 "from sm where usec=%(TS)d and pid=%(PidS)s")) of
 	{selected, [Row]} ->
@@ -97,7 +97,9 @@ delete_session(_LUser, LServer, _LResource, {Now, Pid}) ->
               LServer,
               ?SQL("delete from sm"
                    " where usec=%(TS)d and pid=%(PidS)s")),
-	    {ok, row_to_session(LServer, Row)};
+	    try {ok, row_to_session(LServer, Row)}
+	    catch _:{node_down, _} -> {error, notfound}
+	    end;
 	{selected, []} ->
 	    {error, notfound};
 	Err ->
@@ -114,10 +116,15 @@ get_sessions() ->
 get_sessions(LServer) ->
     case ejabberd_sql:sql_query(
 	   LServer,
-           ?SQL("select @(usec)d, @(pid)s, @(username)s,"
+           ?SQL("select @(usec)d, @(pid)s, @(node)s, @(username)s,"
                 " @(resource)s, @(priority)s, @(info)s from sm")) of
 	{selected, Rows} ->
-	    [row_to_session(LServer, Row) || Row <- Rows];
+	    lists:flatmap(
+	      fun(Row) ->
+		      try [row_to_session(LServer, Row)]
+		      catch _:{node_down, _} -> []
+		      end
+	      end, Rows);
 	Err ->
 	    ?ERROR_MSG("failed to select from 'sm' table: ~p", [Err]),
 	    []
@@ -126,11 +133,16 @@ get_sessions(LServer) ->
 get_sessions(LUser, LServer) ->
     case ejabberd_sql:sql_query(
 	   LServer,
-           ?SQL("select @(usec)d, @(pid)s, @(username)s,"
+           ?SQL("select @(usec)d, @(pid)s, @(node)s, @(username)s,"
                 " @(resource)s, @(priority)s, @(info)s from sm"
                 " where username=%(LUser)s")) of
 	{selected, Rows} ->
-	    [row_to_session(LServer, Row) || Row <- Rows];
+	    lists:flatmap(
+	      fun(Row) ->
+		      try [row_to_session(LServer, Row)]
+		      catch _:{node_down, _} -> []
+		      end
+	      end, Rows);
 	Err ->
 	    ?ERROR_MSG("failed to select from 'sm' table: ~p", [Err]),
 	    []
@@ -139,11 +151,16 @@ get_sessions(LUser, LServer) ->
 get_sessions(LUser, LServer, LResource) ->
     case ejabberd_sql:sql_query(
 	   LServer,
-           ?SQL("select @(usec)d, @(pid)s, @(username)s,"
+           ?SQL("select @(usec)d, @(pid)s, @(node)s, @(username)s,"
                 " @(resource)s, @(priority)s, @(info)s from sm"
                 " where username=%(LUser)s and resource=%(LResource)s")) of
 	{selected, Rows} ->
-	    [row_to_session(LServer, Row) || Row <- Rows];
+	    lists:flatmap(
+	      fun(Row) ->
+		      try [row_to_session(LServer, Row)]
+		      catch _:{node_down, _} -> []
+		      end
+	      end, Rows);
 	Err ->
 	    ?ERROR_MSG("failed to select from 'sm' table: ~p", [Err]),
 	    []
@@ -175,12 +192,39 @@ enc_priority(undefined) ->
 enc_priority(Int) when is_integer(Int) ->
     integer_to_binary(Int).
 
-row_to_session(LServer, {USec, PidS, User, Resource, PrioS, InfoS}) ->
+row_to_session(LServer, {USec, PidS, NodeS, User, Resource, PrioS, InfoS}) ->
     Now = timestamp_to_now(USec),
-    Pid = erlang:list_to_pid(binary_to_list(PidS)),
+    Pid = dec_pid(PidS, NodeS),
     Priority = dec_priority(PrioS),
     Info = ejabberd_sql:decode_term(InfoS),
     #session{sid = {Now, Pid}, us = {User, LServer},
 	     usr = {User, LServer, Resource},
 	     priority = Priority,
 	     info = Info}.
+
+-spec enc_pid(pid()) -> binary().
+enc_pid(Pid) ->
+    list_to_binary(erlang:pid_to_list(Pid)).
+
+-spec dec_pid(binary(), binary()) -> pid().
+dec_pid(PidBin, NodeBin) ->
+    PidStr = binary_to_list(PidBin),
+    Pid = erlang:list_to_pid(PidStr),
+    case erlang:binary_to_atom(NodeBin, latin1) of
+	Node when Node == node() ->
+	    Pid;
+	Node ->
+	    try set_node_id(PidStr, NodeBin)
+	    catch _:badarg ->
+		    erlang:error({node_down, Node})
+	    end
+    end.
+
+-spec set_node_id(string(), binary()) -> pid().
+set_node_id(PidStr, NodeBin) ->
+    ExtPidStr = erlang:pid_to_list(
+		  binary_to_term(
+		    <<131,103,100,(size(NodeBin)):16,NodeBin/binary,0:72>>)),
+    [H|_] = string:tokens(ExtPidStr, "."),
+    [_|T] = string:tokens(PidStr, "."),
+    erlang:list_to_pid(string:join([H|T], ".")).