Handle SIOCSIFMTU ioctl directly so we can apply 802.11-specific bounds.

Note that the min is actually constrained to IF_MINMTU by the if layer.

2 files changed, 18 insertions, 1 deletions

diff --git a/sys/net80211/ieee80211.h b/sys/net80211/ieee80211.h
index 7ad6231..217bbf0 100644
--- a/sys/net80211/ieee80211.h
+++ b/sys/net80211/ieee80211.h
@@ -360,7 +360,16 @@ enum {
 
 #define	IEEE80211_CRC_LEN			4
 
-#define	IEEE80211_MTU				1500
+/*
+ * Maximum acceptable MTU is:
+ *	IEEE80211_MAX_LEN - WEP overhead - CRC -
+ *		QoS overhead - RSN/WPA overhead
+ * Min is arbitrarily chosen > IEEE80211_MIN_LEN.  The default
+ * mtu is Ethernet-compatible; it's set by ether_ifattach.
+ */
+#define	IEEE80211_MTU_MAX			2290
+#define	IEEE80211_MTU_MIN			32
+
 #define	IEEE80211_MAX_LEN			(2300 + IEEE80211_CRC_LEN + \
     (IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN + IEEE80211_WEP_CRCLEN))
 #define	IEEE80211_MIN_LEN \
diff --git a/sys/net80211/ieee80211_ioctl.c b/sys/net80211/ieee80211_ioctl.c
index 64a8879..1c7df74 100644
--- a/sys/net80211/ieee80211_ioctl.c
+++ b/sys/net80211/ieee80211_ioctl.c
@@ -1017,6 +1017,14 @@ ieee80211_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
 		ifr = (struct ifreq *)data;
 		copyout(&ic->ic_stats, ifr->ifr_data, sizeof (ic->ic_stats));
 		break;
+	case SIOCSIFMTU:
+		ifr = (struct ifreq *)data;
+		if (!(IEEE80211_MTU_MIN <= ifr->ifr_mtu &&
+		    ifr->ifr_mtu <= IEEE80211_MTU_MAX))
+			error = EINVAL;
+		else
+			ifp->if_mtu = ifr->ifr_mtu;
+		break;
 	default:
 		error = ether_ioctl(ifp, cmd, data);
 		break;