Fix unportable use of getnameinfo() in pg_hba_file_rules view.

fill_hba_line() thought it could get away with passing sizeof(struct
sockaddr_storage) rather than the actual addrlen previously returned
by getaddrinfo().  While that appears to work on many platforms,
it does not work on FreeBSD 11: you get back a failure, which leads
to the view showing NULL for the address and netmask columns in all
rows.  The POSIX spec for getnameinfo() is pretty clearly on
FreeBSD's side here: you should pass the actual address length.
So it seems plausible that there are other platforms where this
coding also fails, and we just hadn't noticed.

Also, IMO the fact that getnameinfo() failure leads to a NULL output
is pretty bogus in itself.  Our pg_getnameinfo_all() wrapper is
careful to emit "???" on failure, and we should use that in such
cases.  NULL should only be emitted in rows that don't have IP
addresses.

Per bug #16695 from Peter Vandivier.  Back-patch to v10 where this
code was added.

Discussion: https://postgr.es/m/16695-a665558e2f630be7@postgresql.org

src/backend/libpq/hba.c

@@ -1188,8 +1188,11 @@ parse_hba_line(TokenizedLine *tok_line, int elevel)
 
 			ret = pg_getaddrinfo_all(str, NULL, &hints, &gai_result);
 			if (ret == 0 && gai_result)
+			{
 				memcpy(&parsedline->addr, gai_result->ai_addr,
 					   gai_result->ai_addrlen);
+				parsedline->addrlen = gai_result->ai_addrlen;
+			}
 			else if (ret == EAI_NONAME)
 				parsedline->hostname = str;
 			else
@@ -1238,6 +1241,7 @@ parse_hba_line(TokenizedLine *tok_line, int elevel)
 										token->string);
 					return NULL;
 				}
+				parsedline->masklen = parsedline->addrlen;
 				pfree(str);
 			}
 			else if (!parsedline->hostname)
@@ -1288,6 +1292,7 @@ parse_hba_line(TokenizedLine *tok_line, int elevel)
 
 				memcpy(&parsedline->mask, gai_result->ai_addr,
 					   gai_result->ai_addrlen);
+				parsedline->masklen = gai_result->ai_addrlen;
 				pg_freeaddrinfo_all(hints.ai_family, gai_result);
 
 				if (parsedline->addr.ss_family != parsedline->mask.ss_family)
@@ -2538,20 +2543,26 @@ fill_hba_line(Tuplestorestate *tuple_store, TupleDesc tupdesc,
 				}
 				else
 				{
-					if (pg_getnameinfo_all(&hba->addr, sizeof(hba->addr),
-										   buffer, sizeof(buffer),
-										   NULL, 0,
-										   NI_NUMERICHOST) == 0)
+					/*
+					 * Note: if pg_getnameinfo_all fails, it'll set buffer to
+					 * "???", which we want to return.
+					 */
+					if (hba->addrlen > 0)
 					{
-						clean_ipv6_addr(hba->addr.ss_family, buffer);
+						if (pg_getnameinfo_all(&hba->addr, hba->addrlen,
+											   buffer, sizeof(buffer),
+											   NULL, 0,
+											   NI_NUMERICHOST) == 0)
+							clean_ipv6_addr(hba->addr.ss_family, buffer);
 						addrstr = pstrdup(buffer);
 					}
-					if (pg_getnameinfo_all(&hba->mask, sizeof(hba->mask),
-										   buffer, sizeof(buffer),
-										   NULL, 0,
-										   NI_NUMERICHOST) == 0)
+					if (hba->masklen > 0)
 					{
-						clean_ipv6_addr(hba->mask.ss_family, buffer);
+						if (pg_getnameinfo_all(&hba->mask, hba->masklen,
+											   buffer, sizeof(buffer),
+											   NULL, 0,
+											   NI_NUMERICHOST) == 0)
+							clean_ipv6_addr(hba->mask.ss_family, buffer);
 						maskstr = pstrdup(buffer);
 					}
 				}

src/include/libpq/hba.h

@@ -42,6 +42,10 @@ typedef enum UserAuth
 #define USER_AUTH_LAST uaPeer	/* Must be last value of this enum */
 } UserAuth;
 
+/*
+ * Data structures representing pg_hba.conf entries
+ */
+
 typedef enum IPCompareMethod
 {
 	ipCmpMask,
@@ -75,11 +79,12 @@ typedef struct HbaLine
 	List	   *databases;
 	List	   *roles;
 	struct sockaddr_storage addr;
+	int			addrlen;		/* zero if we don't have a valid addr */
 	struct sockaddr_storage mask;
+	int			masklen;		/* zero if we don't have a valid mask */
 	IPCompareMethod ip_cmp_method;
 	char	   *hostname;
 	UserAuth	auth_method;
-
 	char	   *usermap;
 	char	   *pamservice;
 	bool		pam_use_hostname;