caif: Use link layer MTU instead of fixed MTU

Previously CAIF supported maximum transfer size of ~4050.
The transfer size is now calculated dynamically based on the
link layers mtu size.

Signed-off-by: Sjur Braendeland@stericsson.com
Signed-off-by: David S. Miller <davem@davemloft.net>

15 files changed, 173 insertions, 69 deletions

diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index 3e706f00a0d3..3df0c0f8b8bf 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -403,7 +403,6 @@ static void caifdev_setup(struct net_device *dev)
         dev->type = ARPHRD_CAIF;
         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
         dev->mtu = CAIF_MAX_MTU;
-        dev->hard_header_len = CAIF_NEEDED_HEADROOM;
         dev->tx_queue_len = 0;
         dev->destructor = free_netdev;
         skb_queue_head_init(&serdev->head);
diff --git a/include/net/caif/caif_dev.h b/include/net/caif/caif_dev.h
index 318ab9478a44..6da573c75d54 100644
--- a/include/net/caif/caif_dev.h
+++ b/include/net/caif/caif_dev.h
@@ -50,6 +50,9 @@ struct caif_connect_request {
  * @client_layer:       User implementation of client layer. This layer
  *                      MUST have receive and control callback functions
  *                      implemented.
+ * @ifindex:            Link layer interface index used for this connection.
+ * @headroom:           Head room needed by CAIF protocol.
+ * @tailroom:           Tail room needed by CAIF protocol.
  *
  * This function connects a CAIF channel. The Client must implement
  * the struct cflayer. This layer represents the Client layer and holds
@@ -59,8 +62,9 @@ struct caif_connect_request {
  * E.g. CAIF Socket will call this function for each socket it connects
  * and have one client_layer instance for each socket.
  */
-int caif_connect_client(struct caif_connect_request *config,
-                           struct cflayer *client_layer);
+int caif_connect_client(struct caif_connect_request *conn_req,
+                        struct cflayer *client_layer, int *ifindex,
+                        int *headroom, int *tailroom);
 
 /**
  * caif_disconnect_client - Disconnects a client from the CAIF stack.
diff --git a/include/net/caif/caif_layer.h b/include/net/caif/caif_layer.h
index 25c472f0e5b8..c8b07a904e78 100644
--- a/include/net/caif/caif_layer.h
+++ b/include/net/caif/caif_layer.h
@@ -15,14 +15,8 @@ struct cfpktq;
 struct caif_payload_info;
 struct caif_packet_funcs;
 
-#define CAIF_MAX_FRAMESIZE 4096
-#define CAIF_MAX_PAYLOAD_SIZE (4096 - 64)
-#define CAIF_NEEDED_HEADROOM (10)
-#define CAIF_NEEDED_TAILROOM (2)
 
 #define CAIF_LAYER_NAME_SZ 16
-#define CAIF_SUCCESS    1
-#define CAIF_FAILURE    0
 
 /**
  * caif_assert() - Assert function for CAIF.
diff --git a/include/net/caif/cfcnfg.h b/include/net/caif/cfcnfg.h
index 9fc2fc20b884..bd646faffa47 100644
--- a/include/net/caif/cfcnfg.h
+++ b/include/net/caif/cfcnfg.h
@@ -7,6 +7,7 @@
 #ifndef CFCNFG_H_
 #define CFCNFG_H_
 #include <linux/spinlock.h>
+#include <linux/netdevice.h>
 #include <net/caif/caif_layer.h>
 #include <net/caif/cfctrl.h>
 
@@ -73,8 +74,8 @@ void cfcnfg_remove(struct cfcnfg *cfg);
 
 void
 cfcnfg_add_phy_layer(struct cfcnfg *cnfg, enum cfcnfg_phy_type phy_type,
-                     void *dev, struct cflayer *phy_layer, u16 *phyid,
-                     enum cfcnfg_phy_preference pref,
+                     struct net_device *dev, struct cflayer *phy_layer,
+                     u16 *phyid, enum cfcnfg_phy_preference pref,
                      bool fcs, bool stx);
 
 /**
@@ -114,11 +115,18 @@ void cfcnfg_release_adap_layer(struct cflayer *adap_layer);
  * @param:              Link setup parameters.
  * @adap_layer:         Specify the adaptation layer; the receive and
  *                      flow-control functions MUST be set in the structure.
- *
+ * @ifindex:            Link layer interface index used for this connection.
+ * @proto_head:         Protocol head-space needed by CAIF protocol,
+ *                      excluding link layer.
+ * @proto_tail:         Protocol tail-space needed by CAIF protocol,
+ *                      excluding link layer.
  */
 int cfcnfg_add_adaptation_layer(struct cfcnfg *cnfg,
                             struct cfctrl_link_param *param,
-                            struct cflayer *adap_layer);
+                            struct cflayer *adap_layer,
+                            int *ifindex,
+                            int *proto_head,
+                            int *proto_tail);
 
 /**
  * cfcnfg_get_phyid() - Get physical ID, given type.
diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index e2b86f1f5a47..0b586e9d1378 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c
@@ -255,7 +255,7 @@ static int caif_device_notify(struct notifier_block *me, unsigned long what,
                         pref = CFPHYPREF_HIGH_BW;
                         break;
                 }
-
+                dev_hold(dev);
                 cfcnfg_add_phy_layer(get_caif_conf(),
                                      phy_type,
                                      dev,
@@ -285,6 +285,7 @@ static int caif_device_notify(struct notifier_block *me, unsigned long what,
                 caifd->layer.up->ctrlcmd(caifd->layer.up,
                                          _CAIF_CTRLCMD_PHYIF_DOWN_IND,
                                          caifd->layer.id);
+                might_sleep();
                 res = wait_event_interruptible_timeout(caifd->event,
                                         atomic_read(&caifd->in_use) == 0,
                                         TIMEOUT);
@@ -300,6 +301,7 @@ static int caif_device_notify(struct notifier_block *me, unsigned long what,
                                    "Unregistering an active CAIF device: %s\n",
                                    __func__, dev->name);
                 cfcnfg_del_phy_layer(get_caif_conf(), &caifd->layer);
+                dev_put(dev);
                 atomic_set(&caifd->state, what);
                 break;
 
@@ -326,7 +328,8 @@ struct cfcnfg *get_caif_conf(void)
 EXPORT_SYMBOL(get_caif_conf);
 
 int caif_connect_client(struct caif_connect_request *conn_req,
-                           struct cflayer *client_layer)
+                        struct cflayer *client_layer, int *ifindex,
+                        int *headroom, int *tailroom)
 {
         struct cfctrl_link_param param;
         int ret;
@@ -334,8 +337,9 @@ int caif_connect_client(struct caif_connect_request *conn_req,
         if (ret)
                 return ret;
         /* Hook up the adaptation layer. */
-        return cfcnfg_add_adaptation_layer(get_caif_conf(),
-                                                &param, client_layer);
+        return cfcnfg_add_adaptation_layer(get_caif_conf(), &param,
+                                        client_layer, ifindex,
+                                        headroom, tailroom);
 }
 EXPORT_SYMBOL(caif_connect_client);
 
diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 848ae755cdd6..8ce904786116 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -28,8 +28,8 @@
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_NETPROTO(AF_CAIF);
 
-#define CAIF_DEF_SNDBUF (CAIF_MAX_PAYLOAD_SIZE*10)
-#define CAIF_DEF_RCVBUF (CAIF_MAX_PAYLOAD_SIZE*100)
+#define CAIF_DEF_SNDBUF (4096*10)
+#define CAIF_DEF_RCVBUF (4096*100)
 
 /*
  * CAIF state is re-using the TCP socket states.
@@ -76,6 +76,7 @@ struct caifsock {
         struct caif_connect_request conn_req;
         struct mutex readlock;
         struct dentry *debugfs_socket_dir;
+        int headroom, tailroom, maxframe;
 };
 
 static int rx_flow_is_on(struct caifsock *cf_sk)
@@ -594,23 +595,32 @@ static int caif_seqpkt_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 goto err;
         noblock = msg->msg_flags & MSG_DONTWAIT;
 
-        buffer_size = len + CAIF_NEEDED_HEADROOM + CAIF_NEEDED_TAILROOM;
-
         timeo = sock_sndtimeo(sk, noblock);
         timeo = caif_wait_for_flow_on(container_of(sk, struct caifsock, sk),
                                 1, timeo, &ret);
 
+        if (ret)
+                goto err;
         ret = -EPIPE;
         if (cf_sk->sk.sk_state != CAIF_CONNECTED ||
                 sock_flag(sk, SOCK_DEAD) ||
                 (sk->sk_shutdown & RCV_SHUTDOWN))
                 goto err;
 
+        /* Error if trying to write more than maximum frame size. */
+        ret = -EMSGSIZE;
+        if (len > cf_sk->maxframe && cf_sk->sk.sk_protocol != CAIFPROTO_RFM)
+                goto err;
+
+        buffer_size = len + cf_sk->headroom + cf_sk->tailroom;
+
         ret = -ENOMEM;
         skb = sock_alloc_send_skb(sk, buffer_size, noblock, &ret);
-        if (!skb)
+
+        if (!skb || skb_tailroom(skb) < buffer_size)
                 goto err;
-        skb_reserve(skb, CAIF_NEEDED_HEADROOM);
+
+        skb_reserve(skb, cf_sk->headroom);
 
         ret = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
 
@@ -641,7 +651,6 @@ static int caif_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
         long timeo;
 
         err = -EOPNOTSUPP;
-
         if (unlikely(msg->msg_flags&MSG_OOB))
                 goto out_err;
 
@@ -658,8 +667,8 @@ static int caif_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
 
                 size = len-sent;
 
-                if (size > CAIF_MAX_PAYLOAD_SIZE)
-                        size = CAIF_MAX_PAYLOAD_SIZE;
+                if (size > cf_sk->maxframe)
+                        size = cf_sk->maxframe;
 
                 /* If size is more than half of sndbuf, chop up message */
                 if (size > ((sk->sk_sndbuf >> 1) - 64))
@@ -669,14 +678,14 @@ static int caif_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                         size = SKB_MAX_ALLOC;
 
                 skb = sock_alloc_send_skb(sk,
-                                        size + CAIF_NEEDED_HEADROOM
-                                        + CAIF_NEEDED_TAILROOM,
+                                        size + cf_sk->headroom +
+                                        cf_sk->tailroom,
                                         msg->msg_flags&MSG_DONTWAIT,
                                         &err);
                 if (skb == NULL)
                         goto out_err;
 
-                skb_reserve(skb, CAIF_NEEDED_HEADROOM);
+                skb_reserve(skb, cf_sk->headroom);
                 /*
                  *      If you pass two values to the sock_alloc_send_skb
                  *      it tries to grab the large buffer with GFP_NOFS
@@ -817,17 +826,15 @@ static int caif_connect(struct socket *sock, struct sockaddr *uaddr,
         struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);
         long timeo;
         int err;
+        int ifindex, headroom, tailroom;
+        struct net_device *dev;
+
         lock_sock(sk);
 
         err = -EAFNOSUPPORT;
         if (uaddr->sa_family != AF_CAIF)
                 goto out;
 
-        err = -ESOCKTNOSUPPORT;
-        if (unlikely(!(sk->sk_type == SOCK_STREAM &&
-                       cf_sk->sk.sk_protocol == CAIFPROTO_AT) &&
-                       sk->sk_type != SOCK_SEQPACKET))
-                goto out;
         switch (sock->state) {
         case SS_UNCONNECTED:
                 /* Normal case, a fresh connect */
@@ -883,12 +890,23 @@ static int caif_connect(struct socket *sock, struct sockaddr *uaddr,
         dbfs_atomic_inc(&cnt.num_connect_req);
         cf_sk->layer.receive = caif_sktrecv_cb;
         err = caif_connect_client(&cf_sk->conn_req,
-                                &cf_sk->layer);
+                                &cf_sk->layer, &ifindex, &headroom, &tailroom);
         if (err < 0) {
                 cf_sk->sk.sk_socket->state = SS_UNCONNECTED;
                 cf_sk->sk.sk_state = CAIF_DISCONNECTED;
                 goto out;
         }
+        dev = dev_get_by_index(sock_net(sk), ifindex);
+        cf_sk->headroom = LL_RESERVED_SPACE_EXTRA(dev, headroom);
+        cf_sk->tailroom = tailroom;
+        cf_sk->maxframe = dev->mtu - (headroom + tailroom);
+        dev_put(dev);
+        if (cf_sk->maxframe < 1) {
+                pr_warning("CAIF: %s(): CAIF Interface MTU too small (%d)\n",
+                        __func__, dev->mtu);
+                err = -ENODEV;
+                goto out;
+        }
 
         err = -EINPROGRESS;
 wait_connect:
diff --git a/net/caif/cfcnfg.c b/net/caif/cfcnfg.c
index cff2dcb9efe4..1c29189b344d 100644
--- a/net/caif/cfcnfg.c
+++ b/net/caif/cfcnfg.c
@@ -6,6 +6,7 @@
 #include <linux/kernel.h>
 #include <linux/stddef.h>
 #include <linux/slab.h>
+#include <linux/netdevice.h>
 #include <net/caif/caif_layer.h>
 #include <net/caif/cfpkt.h>
 #include <net/caif/cfcnfg.h>
@@ -42,6 +43,15 @@ struct cfcnfg_phyinfo {
 
         /* Information about the physical device */
         struct dev_info dev_info;
+
+        /* Interface index */
+        int ifindex;
+
+        /* Use Start of frame extension */
+        bool use_stx;
+
+        /* Use Start of frame checksum */
+        bool use_fcs;
 };
 
 struct cfcnfg {
@@ -249,9 +259,20 @@ static void cfcnfg_linkdestroy_rsp(struct cflayer *layer, u8 channel_id)
 {
 }
 
+int protohead[CFCTRL_SRV_MASK] = {
+        [CFCTRL_SRV_VEI] = 4,
+        [CFCTRL_SRV_DATAGRAM] = 7,
+        [CFCTRL_SRV_UTIL] = 4,
+        [CFCTRL_SRV_RFM] = 3,
+        [CFCTRL_SRV_DBG] = 3,
+};
+
 int cfcnfg_add_adaptation_layer(struct cfcnfg *cnfg,
                                 struct cfctrl_link_param *param,
-                                struct cflayer *adap_layer)
+                                struct cflayer *adap_layer,
+                                int *ifindex,
+                                int *proto_head,
+                                int *proto_tail)
 {
         struct cflayer *frml;
         if (adap_layer == NULL) {
@@ -277,6 +298,14 @@ int cfcnfg_add_adaptation_layer(struct cfcnfg *cnfg,
                      param->phyid);
         caif_assert(cnfg->phy_layers[param->phyid].phy_layer->id ==
                      param->phyid);
+
+        *ifindex = cnfg->phy_layers[param->phyid].ifindex;
+        *proto_head =
+                protohead[param->linktype]+
+                (cnfg->phy_layers[param->phyid].use_stx ? 1 : 0);
+
+        *proto_tail = 2;
+
         /* FIXME: ENUMERATE INITIALLY WHEN ACTIVATING PHYSICAL INTERFACE */
         cfctrl_enum_req(cnfg->ctrl, param->phyid);
         return cfctrl_linkup_request(cnfg->ctrl, param, adap_layer);
@@ -298,6 +327,8 @@ cfcnfg_linkup_rsp(struct cflayer *layer, u8 channel_id, enum cfctrl_srv serv,
         struct cfcnfg *cnfg = container_obj(layer);
         struct cflayer *servicel = NULL;
         struct cfcnfg_phyinfo *phyinfo;
+        struct net_device *netdev;
+
         if (adapt_layer == NULL) {
                 pr_debug("CAIF: %s(): link setup response "
                                 "but no client exist, send linkdown back\n",
@@ -329,8 +360,9 @@ cfcnfg_linkup_rsp(struct cflayer *layer, u8 channel_id, enum cfctrl_srv serv,
                 servicel = cfdgml_create(channel_id, &phyinfo->dev_info);
                 break;
         case CFCTRL_SRV_RFM:
+                netdev = phyinfo->dev_info.dev;
                 servicel = cfrfml_create(channel_id, &phyinfo->dev_info,
-                                                RFM_FRAGMENT_SIZE);
+                                                netdev->mtu);
                 break;
         case CFCTRL_SRV_UTIL:
                 servicel = cfutill_create(channel_id, &phyinfo->dev_info);
@@ -361,8 +393,8 @@ cfcnfg_linkup_rsp(struct cflayer *layer, u8 channel_id, enum cfctrl_srv serv,
 
 void
 cfcnfg_add_phy_layer(struct cfcnfg *cnfg, enum cfcnfg_phy_type phy_type,
-                     void *dev, struct cflayer *phy_layer, u16 *phyid,
-                     enum cfcnfg_phy_preference pref,
+                     struct net_device *dev, struct cflayer *phy_layer,
+                     u16 *phyid, enum cfcnfg_phy_preference pref,
                      bool fcs, bool stx)
 {
         struct cflayer *frml;
@@ -416,6 +448,10 @@ cfcnfg_add_phy_layer(struct cfcnfg *cnfg, enum cfcnfg_phy_type phy_type,
         cnfg->phy_layers[*phyid].dev_info.dev = dev;
         cnfg->phy_layers[*phyid].phy_layer = phy_layer;
         cnfg->phy_layers[*phyid].phy_ref_count = 0;
+        cnfg->phy_layers[*phyid].ifindex = dev->ifindex;
+        cnfg->phy_layers[*phyid].use_stx = stx;
+        cnfg->phy_layers[*phyid].use_fcs = fcs;
+
         phy_layer->type = phy_type;
         frml = cffrml_create(*phyid, fcs);
         if (!frml) {
diff --git a/net/caif/cfctrl.c b/net/caif/cfctrl.c
index 107c4b2a311e..563145fdc4c3 100644
--- a/net/caif/cfctrl.c
+++ b/net/caif/cfctrl.c
@@ -19,7 +19,7 @@
 #ifdef CAIF_NO_LOOP
 static int handle_loop(struct cfctrl *ctrl,
                               int cmd, struct cfpkt *pkt){
-        return CAIF_FAILURE;
+        return -1;
 }
 #else
 static int handle_loop(struct cfctrl *ctrl,
@@ -395,7 +395,7 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
         cmd = cmdrsp & CFCTRL_CMD_MASK;
         if (cmd != CFCTRL_CMD_LINK_ERR
             && CFCTRL_RSP_BIT != (CFCTRL_RSP_BIT & cmdrsp)) {
-                if (handle_loop(cfctrl, cmd, pkt) == CAIF_FAILURE)
+                if (handle_loop(cfctrl, cmd, pkt) != 0)
                         cmdrsp |= CFCTRL_ERR_BIT;
         }
 
@@ -647,6 +647,6 @@ found:
         default:
                 break;
         }
-        return CAIF_SUCCESS;
+        return 0;
 }
 #endif
diff --git a/net/caif/cfdgml.c b/net/caif/cfdgml.c
index 32d9f0dc8463..ed9d53aff280 100644
--- a/net/caif/cfdgml.c
+++ b/net/caif/cfdgml.c
@@ -17,6 +17,7 @@
 #define DGM_FLOW_OFF 0x81
 #define DGM_FLOW_ON  0x80
 #define DGM_CTRL_PKT_SIZE 1
+#define DGM_MTU 1500
 
 static int cfdgml_receive(struct cflayer *layr, struct cfpkt *pkt);
 static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt);
@@ -89,6 +90,10 @@ static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt)
         if (!cfsrvl_ready(service, &ret))
                 return ret;
 
+        /* STE Modem cannot handle more than 1500 bytes datagrams */
+        if (cfpkt_getlen(pkt) > DGM_MTU)
+                return -EMSGSIZE;
+
         cfpkt_add_head(pkt, &zero, 4);
 
         /* Add info for MUX-layer to route the packet out. */
diff --git a/net/caif/cfpkt_skbuff.c b/net/caif/cfpkt_skbuff.c
index 318b0f4b416e..01f238ff2346 100644
--- a/net/caif/cfpkt_skbuff.c
+++ b/net/caif/cfpkt_skbuff.c
@@ -9,8 +9,8 @@
 #include <linux/hardirq.h>
 #include <net/caif/cfpkt.h>
 
-#define PKT_PREFIX CAIF_NEEDED_HEADROOM
-#define PKT_POSTFIX CAIF_NEEDED_TAILROOM
+#define PKT_PREFIX  16
+#define PKT_POSTFIX 2
 #define PKT_LEN_WHEN_EXTENDING 128
 #define PKT_ERROR(pkt, errmsg) do {        \
     cfpkt_priv(pkt)->erronous = true;      \
diff --git a/net/caif/cfserl.c b/net/caif/cfserl.c
index 965c5baace40..a11fbd68a13d 100644
--- a/net/caif/cfserl.c
+++ b/net/caif/cfserl.c
@@ -14,7 +14,8 @@
 #define container_obj(layr) ((struct cfserl *) layr)
 
 #define CFSERL_STX 0x02
-#define CAIF_MINIUM_PACKET_SIZE 4
+#define SERIAL_MINIUM_PACKET_SIZE 4
+#define SERIAL_MAX_FRAMESIZE 4096
 struct cfserl {
         struct cflayer layer;
         struct cfpkt *incomplete_frm;
@@ -119,8 +120,8 @@ static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
                 /*
                  * Frame error handling
                  */
-                if (expectlen < CAIF_MINIUM_PACKET_SIZE
-                    || expectlen > CAIF_MAX_FRAMESIZE) {
+                if (expectlen < SERIAL_MINIUM_PACKET_SIZE
+                    || expectlen > SERIAL_MAX_FRAMESIZE) {
                         if (!layr->usestx) {
                                 if (pkt != NULL)
                                         cfpkt_destroy(pkt);
diff --git a/net/caif/cfsrvl.c b/net/caif/cfsrvl.c
index 4c9f147c38af..f40939a91211 100644
--- a/net/caif/cfsrvl.c
+++ b/net/caif/cfsrvl.c
@@ -162,7 +162,6 @@ void cfservl_destroy(struct cflayer *layer)
 void cfsrvl_release(struct kref *kref)
 {
         struct cfsrvl *service = container_of(kref, struct cfsrvl, ref);
-        pr_info("CAIF: %s(): enter\n", __func__);
         kfree(service);
 }
 
diff --git a/net/caif/cfutill.c b/net/caif/cfutill.c
index ce525cac9064..02795aff57a4 100644
--- a/net/caif/cfutill.c
+++ b/net/caif/cfutill.c
@@ -90,12 +90,6 @@ static int cfutill_transmit(struct cflayer *layr, struct cfpkt *pkt)
         if (!cfsrvl_ready(service, &ret))
                 return ret;
 
-        if (cfpkt_getlen(pkt) > CAIF_MAX_PAYLOAD_SIZE) {
-                pr_err("CAIF: %s(): packet too large size=%d\n",
-                        __func__, cfpkt_getlen(pkt));
-                return -EOVERFLOW;
-        }
-
         cfpkt_add_head(pkt, &zero, 1);
         /* Add info for MUX-layer to route the packet out. */
         info = cfpkt_info(pkt);
diff --git a/net/caif/cfveil.c b/net/caif/cfveil.c
index 637cb0eee13c..77cc09faac9a 100644
--- a/net/caif/cfveil.c
+++ b/net/caif/cfveil.c
@@ -84,11 +84,6 @@ static int cfvei_transmit(struct cflayer *layr, struct cfpkt *pkt)
                 return ret;
         caif_assert(layr->dn != NULL);
         caif_assert(layr->dn->transmit != NULL);
-        if (cfpkt_getlen(pkt) > CAIF_MAX_PAYLOAD_SIZE) {
-                pr_warning("CAIF: %s(): Packet too large - size=%d\n",
-                           __func__, cfpkt_getlen(pkt));
-                return -EOVERFLOW;
-        }
 
         if (cfpkt_add_head(pkt, &tmp, 1) < 0) {
                 pr_err("CAIF: %s(): Packet is erroneous!\n", __func__);
diff --git a/net/caif/chnl_net.c b/net/caif/chnl_net.c
index 610966abe2dc..4293e190ec53 100644
--- a/net/caif/chnl_net.c
+++ b/net/caif/chnl_net.c
@@ -23,7 +23,7 @@
 #include <net/caif/caif_dev.h>
 
 /* GPRS PDP connection has MTU to 1500 */
-#define SIZE_MTU 1500
+#define GPRS_PDP_MTU 1500
 /* 5 sec. connect timeout */
 #define CONNECT_TIMEOUT (5 * HZ)
 #define CAIF_NET_DEFAULT_QUEUE_LEN 500
@@ -232,6 +232,8 @@ static int chnl_net_open(struct net_device *dev)
 {
         struct chnl_net *priv = NULL;
         int result = -1;
+        int llifindex, headroom, tailroom, mtu;
+        struct net_device *lldev;
         ASSERT_RTNL();
         priv = netdev_priv(dev);
         if (!priv) {
@@ -241,41 +243,88 @@ static int chnl_net_open(struct net_device *dev)
 
         if (priv->state != CAIF_CONNECTING) {
                 priv->state = CAIF_CONNECTING;
-                result = caif_connect_client(&priv->conn_req, &priv->chnl);
+                result = caif_connect_client(&priv->conn_req, &priv->chnl,
+                                        &llifindex, &headroom, &tailroom);
                 if (result != 0) {
-                                priv->state = CAIF_DISCONNECTED;
                                 pr_debug("CAIF: %s(): err: "
                                         "Unable to register and open device,"
                                         " Err:%d\n",
                                         __func__,
                                         result);
-                                return result;
+                                goto error;
+                }
+
+                lldev = dev_get_by_index(dev_net(dev), llifindex);
+
+                if (lldev == NULL) {
+                        pr_debug("CAIF: %s(): no interface?\n", __func__);
+                        result = -ENODEV;
+                        goto error;
+                }
+
+                dev->needed_tailroom = tailroom + lldev->needed_tailroom;
+                dev->hard_header_len = headroom + lldev->hard_header_len +
+                        lldev->needed_tailroom;
+
+                /*
+                 * MTU, head-room etc is not know before we have a
+                 * CAIF link layer device available. MTU calculation may
+                 * override initial RTNL configuration.
+                 * MTU is minimum of current mtu, link layer mtu pluss
+                 * CAIF head and tail, and PDP GPRS contexts max MTU.
+                 */
+                mtu = min_t(int, dev->mtu, lldev->mtu - (headroom + tailroom));
+                mtu = min_t(int, GPRS_PDP_MTU, mtu);
+                dev_set_mtu(dev, mtu);
+                dev_put(lldev);
+
+                if (mtu < 100) {
+                        pr_warning("CAIF: %s(): "
+                                "CAIF Interface MTU too small (%d)\n",
+                                __func__, mtu);
+                        result = -ENODEV;
+                        goto error;
                 }
         }
 
+        rtnl_unlock();  /* Release RTNL lock during connect wait */
+
         result = wait_event_interruptible_timeout(priv->netmgmt_wq,
                                                 priv->state != CAIF_CONNECTING,
                                                 CONNECT_TIMEOUT);
 
+        rtnl_lock();
+
         if (result == -ERESTARTSYS) {
                 pr_debug("CAIF: %s(): wait_event_interruptible"
                          " woken by a signal\n", __func__);
-                return -ERESTARTSYS;
+                result = -ERESTARTSYS;
+                goto error;
         }
+
         if (result == 0) {
                 pr_debug("CAIF: %s(): connect timeout\n", __func__);
                 caif_disconnect_client(&priv->chnl);
                 priv->state = CAIF_DISCONNECTED;
                 pr_debug("CAIF: %s(): state disconnected\n", __func__);
-                return -ETIMEDOUT;
+                result = -ETIMEDOUT;
+                goto error;
         }
 
         if (priv->state != CAIF_CONNECTED) {
                 pr_debug("CAIF: %s(): connect failed\n", __func__);
-                return -ECONNREFUSED;
+                result = -ECONNREFUSED;
+                goto error;
         }
         pr_debug("CAIF: %s(): CAIF Netdevice connected\n", __func__);
         return 0;
+
+error:
+        caif_disconnect_client(&priv->chnl);
+        priv->state = CAIF_DISCONNECTED;
+        pr_debug("CAIF: %s(): state disconnected\n", __func__);
+        return result;
+
 }
 
 static int chnl_net_stop(struct net_device *dev)
@@ -321,9 +370,7 @@ static void ipcaif_net_setup(struct net_device *dev)
         dev->destructor = free_netdev;
         dev->flags |= IFF_NOARP;
         dev->flags |= IFF_POINTOPOINT;
-        dev->needed_headroom = CAIF_NEEDED_HEADROOM;
-        dev->needed_tailroom = CAIF_NEEDED_TAILROOM;
-        dev->mtu = SIZE_MTU;
+        dev->mtu = GPRS_PDP_MTU;
         dev->tx_queue_len = CAIF_NET_DEFAULT_QUEUE_LEN;
 
         priv = netdev_priv(dev);