From b9bea7f640eeef39422fe239b6932befb526d536 Mon Sep 17 00:00:00 2001
From: Bob Halley <halley@dnspython.org>
Date: Thu, 18 Jun 2020 07:20:50 -0700
Subject: [PATCH] Construct socket.gaierror with an errno and a string, as
 doing just the errno doesn't cause the errno field in the exception to be
 set, and thus our exceptions were different and less useful than the stock
 ones.

Adjust gethostbyaddr() to filter addresses like the system one does.
---
 dns/resolver.py | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/dns/resolver.py b/dns/resolver.py
index 272db86a..3cb51ff2 100644
--- a/dns/resolver.py
+++ b/dns/resolver.py
@@ -30,6 +30,7 @@ except ImportError:
 
 import dns.exception
 import dns.flags
+import dns.inet
 import dns.ipv4
 import dns.ipv6
 import dns.message
@@ -1343,9 +1344,10 @@ def _getaddrinfo(host=None, service=None, family=socket.AF_UNSPEC, socktype=0,
         # no EAI_SYSTEM on Windows [Issue #416].  We didn't go for
         # EAI_BADFLAGS as the flags aren't bad, we just don't
         # implement them.
-        raise socket.gaierror(socket.EAI_FAIL)
+        raise socket.gaierror(socket.EAI_FAIL,
+                              'Non-recoverable failure in name resolution')
     if host is None and service is None:
-        raise socket.gaierror(socket.EAI_NONAME)
+        raise socket.gaierror(socket.EAI_NONAME, 'Name or service not known')
     v6addrs = []
     v4addrs = []
     canonical_name = None
@@ -1384,12 +1386,14 @@ def _getaddrinfo(host=None, service=None, family=socket.AF_UNSPEC, socktype=0,
                 for rdata in v4.rrset:
                     v4addrs.append(rdata.address)
     except dns.resolver.NXDOMAIN:
-        raise socket.gaierror(socket.EAI_NONAME)
-    except Exception:
+        raise socket.gaierror(socket.EAI_NONAME, 'Name or service not known')
+    except Exception as e:
+        print(e)
         # We raise EAI_AGAIN here as the failure may be temporary
         # (e.g. a timeout) and EAI_SYSTEM isn't defined on Windows.
         # [Issue #416]
-        raise socket.gaierror(socket.EAI_AGAIN)
+        raise socket.gaierror(socket.EAI_AGAIN,
+                              'Temporary failure in name resolution')
     port = None
     try:
         # Is it a port literal?
@@ -1404,7 +1408,7 @@ def _getaddrinfo(host=None, service=None, family=socket.AF_UNSPEC, socktype=0,
             except Exception:
                 pass
     if port is None:
-        raise socket.gaierror(socket.EAI_NONAME)
+        raise socket.gaierror(socket.EAI_NONAME, 'Name or service not known')
     tuples = []
     if socktype == 0:
         socktypes = [socket.SOCK_DGRAM, socket.SOCK_STREAM]
@@ -1427,7 +1431,7 @@ def _getaddrinfo(host=None, service=None, family=socket.AF_UNSPEC, socktype=0,
                     tuples.append((socket.AF_INET, socktype, proto,
                                    cname, (addr, port)))
     if len(tuples) == 0:
-        raise socket.gaierror(socket.EAI_NONAME)
+        raise socket.gaierror(socket.EAI_NONAME, 'Name or service not known')
     return tuples
 
 
@@ -1456,7 +1460,8 @@ def _getnameinfo(sockaddr, flags=0):
             hostname = answer.rrset[0].target.to_text(True)
         except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
             if flags & socket.NI_NAMEREQD:
-                raise socket.gaierror(socket.EAI_NONAME)
+                raise socket.gaierror(socket.EAI_NONAME,
+                                      'Name or service not known')
             hostname = addr
             if scope is not None:
                 hostname += '%' + str(scope)
@@ -1510,8 +1515,20 @@ def _gethostbyaddr(ip):
     tuples = _getaddrinfo(name, 0, family, socket.SOCK_STREAM, socket.SOL_TCP,
                           socket.AI_CANONNAME)
     canonical = tuples[0][3]
+    # We only want to include an address from the tuples if it's the
+    # same as the one we asked about.  We do this comparison in binary
+    # to avoid any differences in text representations.
+    try:
+        bin_ip = dns.inet.inet_pton(family, ip)
+    except Exception:
+        # socket.getfqdn() apparently calls gethostbyaddr() with a name,
+        # and this all works, so do what it does.
+        bin_ip = None
     for item in tuples:
-        addresses.append(item[4][0])
+        addr = item[4][0]
+        bin_addr = dns.inet.inet_pton(family, addr)
+        if bin_ip is None or bin_ip == bin_addr:
+            addresses.append(addr)
     # XXX we just ignore aliases
     return (canonical, aliases, addresses)
 
-- 
2.47.3