ieee802154: 6lowpan: ensure MTU of 1280 for 6lowpan

This patch drops the userspace accessable sysfs entry for the maximum
datagram size of a 6LoWPAN fragment packet.

A fragment should not have a datagram size value greater than 1280 byte.
Instead of make this value configurable, we accept 1280 datagram size
fragment packets only.

Signed-off-by: Martin Townsend <martin.townsend@xsilon.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 3 insertions, 12 deletions

diff --git a/net/ieee802154/reassembly.c b/net/ieee802154/reassembly.c
index ffec6ce51005..32755cb7e64e 100644
--- a/net/ieee802154/reassembly.c
+++ b/net/ieee802154/reassembly.c
@@ -355,8 +355,6 @@ int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type)
         struct net *net = dev_net(skb->dev);
         struct lowpan_frag_info *frag_info = lowpan_cb(skb);
         struct ieee802154_addr source, dest;
-        struct netns_ieee802154_lowpan *ieee802154_lowpan =
-                net_ieee802154_lowpan(net);
         int err;
 
         source = mac_cb(skb)->source;
@@ -366,8 +364,10 @@ int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type)
         if (err < 0)
                 goto err;
 
-        if (frag_info->d_size > ieee802154_lowpan->max_dsize)
+        if (frag_info->d_size > IPV6_MIN_MTU) {
+                net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
                 goto err;
+        }
 
         fq = fq_find(net, frag_info, &source, &dest);
         if (fq != NULL) {
@@ -415,13 +415,6 @@ static struct ctl_table lowpan_frags_ns_ctl_table[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec_jiffies,
         },
-        {
-                .procname       = "6lowpanfrag_max_datagram_size",
-                .data           = &init_net.ieee802154_lowpan.max_dsize,
-                .maxlen         = sizeof(int),
-                .mode           = 0644,
-                .proc_handler   = proc_dointvec
-        },
         { }
 };
 
@@ -458,7 +451,6 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
                 table[1].data = &ieee802154_lowpan->frags.low_thresh;
                 table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;
                 table[2].data = &ieee802154_lowpan->frags.timeout;
-                table[3].data = &ieee802154_lowpan->max_dsize;
 
                 /* Don't export sysctls to unprivileged users */
                 if (net->user_ns != &init_user_ns)
@@ -533,7 +525,6 @@ static int __net_init lowpan_frags_init_net(struct net *net)
         ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
         ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
         ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
-        ieee802154_lowpan->max_dsize = 0xFFFF;
 
         inet_frags_init_net(&ieee802154_lowpan->frags);