Phonet: emit errors when a packet cannot be delivered locally

When there is no listener socket for a received packet, send an error
back to the sender.

Signed-off-by: Remi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 129 insertions, 4 deletions

diff --git a/include/linux/phonet.h b/include/linux/phonet.h
index 001c0e679099..3a027f588a4a 100644
--- a/include/linux/phonet.h
+++ b/include/linux/phonet.h
@@ -45,6 +45,38 @@ struct phonethdr {
         __u8    pn_sobj;
 } __attribute__((packed));
 
+/* Common Phonet payload header */
+struct phonetmsg {
+        __u8    pn_trans_id;    /* transaction ID */
+        __u8    pn_msg_id;      /* message type */
+        union {
+                struct {
+                        __u8    pn_submsg_id;   /* message subtype */
+                        __u8    pn_data[5];
+                } base;
+                struct {
+                        __u16   pn_e_res_id;    /* extended resource ID */
+                        __u8    pn_e_submsg_id; /* message subtype */
+                        __u8    pn_e_data[3];
+                } ext;
+        } pn_msg_u;
+};
+#define PN_COMMON_MESSAGE       0xF0
+#define PN_PREFIX               0xE0 /* resource for extended messages */
+#define pn_submsg_id            pn_msg_u.base.pn_submsg_id
+#define pn_e_submsg_id          pn_msg_u.ext.pn_e_submsg_id
+#define pn_e_res_id             pn_msg_u.ext.pn_e_res_id
+#define pn_data                 pn_msg_u.base.pn_data
+#define pn_e_data               pn_msg_u.ext.pn_e_data
+
+/* data for unreachable errors */
+#define PN_COMM_SERVICE_NOT_IDENTIFIED_RESP     0x01
+#define PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP   0x14
+#define pn_orig_msg_id          pn_data[0]
+#define pn_status               pn_data[1]
+#define pn_e_orig_msg_id        pn_e_data[0]
+#define pn_e_status             pn_e_data[1]
+
 /* Phonet socket address structure */
 struct sockaddr_pn {
         sa_family_t spn_family;
diff --git a/include/net/phonet/phonet.h b/include/net/phonet/phonet.h
index 1c6f7e7d5fea..d4e72508e145 100644
--- a/include/net/phonet/phonet.h
+++ b/include/net/phonet/phonet.h
@@ -60,6 +60,11 @@ static inline struct phonethdr *pn_hdr(struct sk_buff *skb)
         return (struct phonethdr *)skb_network_header(skb);
 }
 
+static inline struct phonetmsg *pn_msg(struct sk_buff *skb)
+{
+        return (struct phonetmsg *)skb_transport_header(skb);
+}
+
 /*
  * Get the other party's sockaddr from received skb. The skb begins
  * with a Phonet header.
diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
index 50dc258d5aa2..1d8df6b7e3df 100644
--- a/net/phonet/af_phonet.c
+++ b/net/phonet/af_phonet.c
@@ -132,7 +132,7 @@ EXPORT_SYMBOL(phonet_header_ops);
  * Prepends an ISI header and sends a datagram.
  */
 static int pn_send(struct sk_buff *skb, struct net_device *dev,
-                        u16 dst, u16 src, u8 res)
+                        u16 dst, u16 src, u8 res, u8 irq)
 {
         struct phonethdr *ph;
         int err;
@@ -163,7 +163,10 @@ static int pn_send(struct sk_buff *skb, struct net_device *dev,
                 skb_reset_mac_header(skb);
                 skb->pkt_type = PACKET_LOOPBACK;
                 skb_orphan(skb);
-                netif_rx_ni(skb);
+                if (irq)
+                        netif_rx(skb);
+                else
+                        netif_rx_ni(skb);
                 err = 0;
         } else {
                 err = dev_hard_header(skb, dev, ntohs(skb->protocol),
@@ -181,6 +184,19 @@ drop:
         return err;
 }
 
+static int pn_raw_send(const void *data, int len, struct net_device *dev,
+                        u16 dst, u16 src, u8 res)
+{
+        struct sk_buff *skb = alloc_skb(MAX_PHONET_HEADER + len, GFP_ATOMIC);
+        if (skb == NULL)
+                return -ENOMEM;
+
+        skb_reserve(skb, MAX_PHONET_HEADER);
+        __skb_put(skb, len);
+        skb_copy_to_linear_data(skb, data, len);
+        return pn_send(skb, dev, dst, src, res, 1);
+}
+
 /*
  * Create a Phonet header for the skb and send it out. Returns
  * non-zero error code if failed. The skb is freed then.
@@ -211,7 +227,7 @@ int pn_skb_send(struct sock *sk, struct sk_buff *skb,
                 src = pn_object(saddr, pn_obj(src));
 
         err = pn_send(skb, dev, pn_sockaddr_get_object(target),
-                        src, pn_sockaddr_get_resource(target));
+                        src, pn_sockaddr_get_resource(target), 0);
         dev_put(dev);
         return err;
 
@@ -223,6 +239,73 @@ drop:
 }
 EXPORT_SYMBOL(pn_skb_send);
 
+/* Do not send an error message in response to an error message */
+static inline int can_respond(struct sk_buff *skb)
+{
+        const struct phonethdr *ph;
+        const struct phonetmsg *pm;
+        u8 submsg_id;
+
+        if (!pskb_may_pull(skb, 3))
+                return 0;
+
+        ph = pn_hdr(skb);
+        if (phonet_address_get(skb->dev, ph->pn_rdev) != ph->pn_rdev)
+                return 0; /* we are not the destination */
+        if (ph->pn_res == PN_PREFIX && !pskb_may_pull(skb, 5))
+                return 0;
+
+        ph = pn_hdr(skb); /* re-acquires the pointer */
+        pm = pn_msg(skb);
+        if (pm->pn_msg_id != PN_COMMON_MESSAGE)
+                return 1;
+        submsg_id = (ph->pn_res == PN_PREFIX)
+                ? pm->pn_e_submsg_id : pm->pn_submsg_id;
+        if (submsg_id != PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP &&
+                pm->pn_e_submsg_id != PN_COMM_SERVICE_NOT_IDENTIFIED_RESP)
+                return 1;
+        return 0;
+}
+
+static int send_obj_unreachable(struct sk_buff *rskb)
+{
+        const struct phonethdr *oph = pn_hdr(rskb);
+        const struct phonetmsg *opm = pn_msg(rskb);
+        struct phonetmsg resp;
+
+        memset(&resp, 0, sizeof(resp));
+        resp.pn_trans_id = opm->pn_trans_id;
+        resp.pn_msg_id = PN_COMMON_MESSAGE;
+        if (oph->pn_res == PN_PREFIX) {
+                resp.pn_e_res_id = opm->pn_e_res_id;
+                resp.pn_e_submsg_id = PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP;
+                resp.pn_e_orig_msg_id = opm->pn_msg_id;
+                resp.pn_e_status = 0;
+        } else {
+                resp.pn_submsg_id = PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP;
+                resp.pn_orig_msg_id = opm->pn_msg_id;
+                resp.pn_status = 0;
+        }
+        return pn_raw_send(&resp, sizeof(resp), rskb->dev,
+                                pn_object(oph->pn_sdev, oph->pn_sobj),
+                                pn_object(oph->pn_rdev, oph->pn_robj),
+                                oph->pn_res);
+}
+
+static int send_reset_indications(struct sk_buff *rskb)
+{
+        struct phonethdr *oph = pn_hdr(rskb);
+        static const u8 data[4] = {
+                0x00 /* trans ID */, 0x10 /* subscribe msg */,
+                0x00 /* subscription count */, 0x00 /* dummy */
+        };
+
+        return pn_raw_send(data, sizeof(data), rskb->dev,
+                                pn_object(oph->pn_sdev, 0x00),
+                                pn_object(oph->pn_rdev, oph->pn_robj), 0x10);
+}
+
+
 /* packet type functions */
 
 /*
@@ -260,8 +343,13 @@ static int phonet_rcv(struct sk_buff *skb, struct net_device *dev,
                 goto out; /* currently, we cannot be device 0 */
 
         sk = pn_find_sock_by_sa(&sa);
-        if (sk == NULL)
+        if (sk == NULL) {
+                if (can_respond(skb)) {
+                        send_obj_unreachable(skb);
+                        send_reset_indications(skb);
+                }
                 goto out;
+        }