From 6bb5d4c4e20c8ee603bdcec7be6d2855c13dadba Mon Sep 17 00:00:00 2001
From: Alexis Christoforides <alexis@thenull.net>
Date: Fri, 17 Aug 2018 00:07:19 +0300
Subject: [PATCH] [runtime] Use getprotobyname_r() where needed and available

Fixes https://github.com/mono/mono/issues/7087
---
 configure.ac                  | 17 +++++++++++++++++
 mono/utils/networking-posix.c | 23 ++++++++++++++++++++---
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index c9b895d220d35..96cbe154a80a8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2286,6 +2286,23 @@ if test x$host_win32 = xno; then
 		AC_MSG_RESULT(no)
 	])
 
+	dnl **********************************
+	dnl *** Check for getprotobyname_r ***
+	dnl **********************************
+	AC_MSG_CHECKING(for getprotobyname_r)
+		AC_TRY_LINK([
+		#include <stdio.h>
+		#include <netdb.h>
+	], [
+		getprotobyname_r(NULL, NULL, NULL, 0, NULL);
+	], [
+		# Yes, we have it...
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_GETPROTOBYNAME_R, 1, [Have getprotobyname_r])
+	], [
+		AC_MSG_RESULT(no)
+	])
+
 	dnl **********************************
 	dnl *** Check for getnameinfo ***
 	dnl **********************************
diff --git a/mono/utils/networking-posix.c b/mono/utils/networking-posix.c
index 85a6eba551f2f..142f4f846fbb9 100644
--- a/mono/utils/networking-posix.c
+++ b/mono/utils/networking-posix.c
@@ -127,7 +127,24 @@ mono_get_address_info (const char *hostname, int port, int flags, MonoAddressInf
 
 #endif
 
-#ifdef HAVE_GETPROTOBYNAME
+#if defined(__linux__) && defined(HAVE_GETPROTOBYNAME_R)
+
+static int
+fetch_protocol (const char *proto_name, int *cache, int *proto, int default_val)
+{
+	if (!*cache) {
+		struct protoent protoent_buf = { 0 };
+		struct protoent *pent = NULL;
+		char buf[1024];
+
+		getprotobyname_r (proto_name, &protoent_buf, buf, 1024, &pent);
+		*proto = pent ? pent->p_proto : default_val;
+		*cache = 1;
+	}
+	return *proto;
+}
+
+#elif HAVE_GETPROTOBYNAME
 
 static int
 fetch_protocol (const char *proto_name, int *cache, int *proto, int default_val)
@@ -142,6 +159,8 @@ fetch_protocol (const char *proto_name, int *cache, int *proto, int default_val)
 	return *proto;
 }
 
+#endif
+
 int
 mono_networking_get_tcp_protocol (void)
 {
@@ -163,8 +182,6 @@ mono_networking_get_ipv6_protocol (void)
 	return fetch_protocol ("ipv6", &cache, &proto, 41); //41 is SOL_IPV6 on linux
 }
 
-#endif
-
 #if defined (HAVE_SIOCGIFCONF)
 
 #define IFCONF_BUFF_SIZE 1024