WIP: ggsn: apply configured APN MTU to tun

Change-Id: Ifae556169d895860812c9ea5633292d7e3fab338
---
M ggsn/ggsn.c
M ggsn/ggsn.h
M ggsn/ggsn_vty.c
3 files changed, 33 insertions(+), 3 deletions(-)


git pull ssh://gerrit.osmocom.org:29418/osmo-ggsn refs/changes/84/38484/1

diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c
index 1908958..53b5213 100644
--- a/ggsn/ggsn.c
+++ b/ggsn/ggsn.c
@@ -309,6 +309,16 @@
 		return -1;
 	}
 
+	if (apn->tun.cfg.mtu_apply) {
+		rc = osmo_netdev_set_mtu(apn->tun.tun->netdev, apn->cfg.mtu);
+		if (rc < 0) {
+			LOGPAPN(LOGL_ERROR, apn, "Failed to set tun interface MTU %u: %s\n",
+				apn->cfg.mtu, strerror(errno));
+			apn_stop(apn);
+			return -1;
+		}
+	}
+
 	if (apn->tun.cfg.ipup_script) {
 		LOGPAPN(LOGL_INFO, apn, "Running ip-up script %s\n",
 			apn->tun.cfg.ipup_script);
diff --git a/ggsn/ggsn.h b/ggsn/ggsn.h
index bd953a4..23df05e 100644
--- a/ggsn/ggsn.h
+++ b/ggsn/ggsn.h
@@ -95,6 +95,8 @@
 			/* ip-up and ip-down script names/paths */
 			char *ipup_script;
 			char *ipdown_script;
+			/* Whether to apply the MTU (apn->cfg.mtu) on the tun device: */
+			bool mtu_apply;
 		} cfg;
 		struct tun_t *tun;
 	} tun;
diff --git a/ggsn/ggsn_vty.c b/ggsn/ggsn_vty.c
index eda0096..b0f07fe 100644
--- a/ggsn/ggsn_vty.c
+++ b/ggsn/ggsn_vty.c
@@ -422,16 +422,33 @@
 /* MAX_POSSIBLE_APN_MTU = 9000
  * MAX_DESIRED_APN_MTU = 1420 */
 DEFUN(cfg_apn_mtu, cfg_apn_mtu_cmd,
-	"mtu (<0-" OSMO_STRINGIFY_VAL(MAX_POSSIBLE_APN_MTU) ">|default)",
+	"mtu (<0-" OSMO_STRINGIFY_VAL(MAX_POSSIBLE_APN_MTU) ">|default) [apply]",
 	"Configure announced MTU\n"
 	"MTU of the APN, announced to the UE\n"
-	"Default value of the MTU of the APN (1420)\n")
+	"Default value of the MTU of the APN (1420)\n"
+	"Apply the MTU on the tun-device of the APN\n")
 {
 	struct apn_ctx *apn = (struct apn_ctx *) vty->index;
+	int rc;
+
 	if (strcmp(argv[0], "default") == 0)
 		apn->cfg.mtu = MAX_DESIRED_APN_MTU;
 	else
 		apn->cfg.mtu = atoi(argv[0]);
+	apn->tun.cfg.mtu_apply = (argc > 1);
+
+	if (apn->tun.cfg.mtu_apply && apn->tun.tun) {
+		rc = osmo_netdev_set_mtu(apn->tun.tun->netdev, apn->cfg.mtu);
+		if (rc < 0) {
+			char buf_err[128];
+			strerror_r(errno, buf_err, sizeof(buf_err));
+			LOGPAPN(LOGL_ERROR, apn, "Failed to set tun interface MTU %u: %s (%d)\n",
+				apn->cfg.mtu, buf_err, rc);
+			vty_out(vty, "%% Failed to set tun interface MTU %u: %s (%d)%s",
+				apn->cfg.mtu, buf_err, rc, VTY_NEWLINE);
+			return CMD_WARNING;
+		}
+	}
 	return CMD_SUCCESS;
 }
 
@@ -705,7 +722,8 @@
 			VTY_NEWLINE);
 	}
 
-	vty_out(vty, "  mtu %" PRIu16 "%s", apn->cfg.mtu, VTY_NEWLINE);
+	vty_out(vty, "  mtu %" PRIu16 "%s%s", apn->cfg.mtu,
+		apn->tun.cfg.mtu_apply ? " apply" : "", VTY_NEWLINE);
 
 	if (!apn->cfg.tx_gpdu_seq)
 		vty_out(vty, "  no g-pdu tx-sequence-numbers%s", VTY_NEWLINE);

