Fix TLS tests on newer tcl-tls/OpenSSL. (#10910)

Before this commit, TLS tests on Ubuntu 22.04 would fail as dropped
connections result with an ECONNABORTED error thrown instead of an empty
read.

(cherry picked from commit 69d5576832)

tests/support/redis.tcl

@@ -66,6 +66,33 @@ proc redis {{server 127.0.0.1} {port 6379} {defer 0} {tls 0} {tlsoptions {}} {re
     interp alias {} ::redis::redisHandle$id {} ::redis::__dispatch__ $id
 }
 
+# On recent versions of tcl-tls/OpenSSL, reading from a dropped connection
+# results with an error we need to catch and mimic the old behavior.
+proc ::redis::redis_safe_read {fd len} {
+    if {$len == -1} {
+        set err [catch {set val [read $fd]} msg]
+    } else {
+        set err [catch {set val [read $fd $len]} msg]
+    }
+    if {!$err} {
+        return $val
+    }
+    if {[string match "*connection abort*" $msg]} {
+        return {}
+    }
+    error $msg
+}
+
+proc ::redis::redis_safe_gets {fd} {
+    if {[catch {set val [gets $fd]} msg]} {
+        if {[string match "*connection abort*" $msg]} {
+            return {}
+        }
+        error $msg
+    }
+    return $val
+}
+
 # This is a wrapper to the actual dispatching procedure that handles
 # reconnection if needed.
 proc ::redis::__dispatch__ {id method args} {
@@ -192,8 +219,8 @@ proc ::redis::redis_writenl {fd buf} {
 }
 
 proc ::redis::redis_readnl {fd len} {
-    set buf [read $fd $len]
+    set buf [redis_safe_read $fd $len]
-    read $fd 2 ; # discard CR LF
+    redis_safe_read $fd 2 ; # discard CR LF
     return $buf
 }
 
@@ -239,11 +266,11 @@ proc ::redis::redis_read_map {id fd} {
 }
 
 proc ::redis::redis_read_line fd {
-    string trim [gets $fd]
+    string trim [redis_safe_gets $fd]
 }
 
 proc ::redis::redis_read_null fd {
-    gets $fd
+    redis_safe_gets $fd
     return {}
 }
 
@@ -266,7 +293,7 @@ proc ::redis::redis_read_reply {id fd} {
     }
 
     while {1} {
-        set type [read $fd 1]
+        set type [redis_safe_read $fd 1]
         switch -exact -- $type {
             _ {return [redis_read_null $fd]}
             : -

tests/unit/obuf-limits.tcl

@@ -111,7 +111,7 @@ start_server {tags {"obuf-limits"}} {
 
         # Read nothing
         set fd [$rd channel]
-        assert_equal {} [read $fd]
+        assert_equal {} [$rd rawread]
     }
 
     # Note: This test assumes that what's written with one write, will be read by redis in one read.
@@ -151,8 +151,7 @@ start_server {tags {"obuf-limits"}} {
         assert_equal "PONG" [r ping]
         set clients [r client list]
         assert_no_match "*name=multicommands*" $clients
-        set fd [$rd2 channel]
+        assert_equal {} [$rd2 rawread]
-        assert_equal {} [read $fd]
     }
 
     test {Execute transactions completely even if client output buffer limit is enforced} {