Change in osmo-ggsn[master]: sgsnemu: Fix build/run against linux < 4.11 (no sysctl addr_gen_mode ...

[pespin]

pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-ggsn/+/17861 )


Change subject: sgsnemu: Fix build/run against linux < 4.11 (no sysctl addr_gen_mode support)
......................................................................

sgsnemu: Fix build/run against linux < 4.11 (no sysctl addr_gen_mode support)

On older systems (like debian 8), the enum is not present in the header
file and build will fail (as saw in osmocom's OBS instance).
Furthermore, the sysctl to change the value was added at a later point
in time, which means compiling can go fine but running may fail due to
the sysctl not being available.

Change-Id: I208970d5b16ea7148444d414b0a6f68c8d9a086c
---
M configure.ac
M sgsnemu/sgsnemu.c
2 files changed, 20 insertions(+), 5 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-ggsn refs/changes/61/17861/1

diff --git a/configure.ac b/configure.ac
index c695958..0e61729 100644
--- a/configure.ac
+++ b/configure.ac
@@ -131,6 +131,15 @@
  AC_DEFINE([HAVE_IPHDR])],
  AC_MSG_RESULT(no))
 
+# Address generation modes (enum) implemented in linux 3.17 (bc91b0f07ada5535427373a4e2050877bcc12218)
+# /proc/sys/net/ipv6/conf/${iface}/addr_gen_mode was added in linux 4.11 (d35a00b8e33dab7385f724e713ae71c8be0a49f4)
+AC_MSG_CHECKING(whether enum in6_addr_gen_mode.IN6_ADDR_GEN_MODE_NONE exists)
+AH_TEMPLATE(HAVE_IN6_ADDR_GEN_MODE_NONE)
+AC_EGREP_HEADER(IN6_ADDR_GEN_MODE_NONE, linux/if_link.h,
+[AC_MSG_RESULT(yes)
+ AC_DEFINE([HAVE_IN6_ADDR_GEN_MODE_NONE])],
+ AC_MSG_RESULT(no))
+
 # Checks for library functions.
 AC_PROG_GCC_TRADITIONAL
 # AC_FUNC_MALLOC
diff --git a/sgsnemu/sgsnemu.c b/sgsnemu/sgsnemu.c
index 1607102..4c51157 100644
--- a/sgsnemu/sgsnemu.c
+++ b/sgsnemu/sgsnemu.c
@@ -15,6 +15,8 @@
  *
  */
 
+#include "config.h"
+
 #ifdef __linux__
 #define _GNU_SOURCE 1		/* strdup() prototype, broken arpa/inet.h */
 #endif
@@ -47,10 +49,11 @@
 #include <time.h>
 
 #if defined(__linux__)
+#if defined(HAVE_IN6_ADDR_GEN_MODE_NONE)
 #include <linux/if_link.h>
+#endif // HAVE_IN6_ADDR_GEN_MODE_NONE
 #endif
 
-#include "config.h"
 #include "../lib/tun.h"
 #include "../lib/ippool.h"
 #include "../lib/syserr.h"
@@ -1920,13 +1923,16 @@
 			exit(1);
 		}
 
-#if defined(__linux__)
-		/* Avoid tunnel setting its own link-local addr automatically, we don't need it. */
+#if defined(__linux__) && defined(HAVE_IN6_ADDR_GEN_MODE_NONE)
+		/* Avoid tunnel setting its own link-local addr automatically,
+		   we don't need it. Don't exit on error since this sysctl is
+		   only available starting with linux 4.11. */
 		snprintf(buf, sizeof(buf), "%u", IN6_ADDR_GEN_MODE_NONE);
 		if (proc_ipv6_conf_write(options.tun_dev_name, "addr_gen_mode", buf) < 0) {
 			SYS_ERR(DSGSN, LOGL_ERROR, errno,
-				"Failed to disable addr_gen_mode on %s\n", options.tun_dev_name);
-			exit(1);
+				"Failed to disable addr_gen_mode on %s, an extra link-local "
+				"ip address will appear on the tun device.\n",
+				options.tun_dev_name);
 		}
 #endif
 

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Gerrit-Project: osmo-ggsn
Gerrit-Branch: master
Gerrit-Change-Id: I208970d5b16ea7148444d414b0a6f68c8d9a086c
Gerrit-Change-Number: 17861
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <pespin at sysmocom.de>
Gerrit-MessageType: newchange
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