[LLC]: Fix the accept path

Borrowing the structure of TCP/IP for this. On the receive of new connections I
was bh_lock_socking the _new_ sock, not the listening one, duh, now it survives
the ssh connections storm I've been using to test this specific bug.

Also fixes send side skb sock accounting.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

1 files changed, 95 insertions, 47 deletions

diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 76f94e0d840d..e10ce5adb104 100644
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -58,7 +58,7 @@ int sysctl_llc2_busy_timeout = LLC2_BUSY_TIME * HZ;
 int llc_conn_state_process(struct sock *sk, struct sk_buff *skb)
 {
         int rc;
-        struct llc_sock *llc = llc_sk(sk);
+        struct llc_sock *llc = llc_sk(skb->sk);
         struct llc_conn_state_ev *ev = llc_conn_ev(skb);
 
         /*
@@ -68,7 +68,10 @@ int llc_conn_state_process(struct sock *sk, struct sk_buff *skb)
          */
         skb_get(skb);
         ev->ind_prim = ev->cfm_prim = 0;
-        rc = llc_conn_service(sk, skb); /* sending event to state machine */
+        /*
+         * Send event to state machine
+         */
+        rc = llc_conn_service(skb->sk, skb);
         if (unlikely(rc != 0)) {
                 printk(KERN_ERR "%s: llc_conn_service failed\n", __FUNCTION__);
                 goto out_kfree_skb;
@@ -100,18 +103,14 @@ int llc_conn_state_process(struct sock *sk, struct sk_buff *skb)
                         kfree_skb(skb);
                 }
                 break;
-        case LLC_CONN_PRIM: {
-                struct sock *parent = skb->sk;
-
-                skb_orphan(skb);
+        case LLC_CONN_PRIM:
                 /*
-                 * Set the skb->sk to the new struct sock, so that at accept
-                 * type the upper layer can get the newly created struct sock.
+                 * Can't be sock_queue_rcv_skb, because we have to leave the
+                 * skb->sk pointing to the newly created struct sock in
+                 * llc_conn_handler. -acme
                  */
-                skb->sk = sk;
-                skb_queue_tail(&parent->sk_receive_queue, skb);
-                sk->sk_state_change(parent);
-        }
+                skb_queue_tail(&sk->sk_receive_queue, skb);
+                sk->sk_state_change(sk);
                 break;
         case LLC_DISC_PRIM:
                 sock_hold(sk);
@@ -475,7 +474,7 @@ static int llc_exec_conn_trans_actions(struct sock *sk,
 }
 
 /**
- *      llc_lookup_established - Finds connection for the remote/local sap/mac
+ *      __llc_lookup_established - Finds connection for the remote/local sap/mac
  *      @sap: SAP
  *      @daddr: address of remote LLC (MAC + SAP)
  *      @laddr: address of local LLC (MAC + SAP)
@@ -483,14 +482,16 @@ static int llc_exec_conn_trans_actions(struct sock *sk,
  *      Search connection list of the SAP and finds connection using the remote
  *      mac, remote sap, local mac, and local sap. Returns pointer for
  *      connection found, %NULL otherwise.
+ *      Caller has to make sure local_bh is disabled.
  */
-struct sock *llc_lookup_established(struct llc_sap *sap, struct llc_addr *daddr,
-                                    struct llc_addr *laddr)
+static struct sock *__llc_lookup_established(struct llc_sap *sap,
+                                             struct llc_addr *daddr,
+                                             struct llc_addr *laddr)
 {
         struct sock *rc;
         struct hlist_node *node;
 
-        read_lock_bh(&sap->sk_list.lock);
+        read_lock(&sap->sk_list.lock);
         sk_for_each(rc, node, &sap->sk_list.list) {
                 struct llc_sock *llc = llc_sk(rc);
 
@@ -504,10 +505,22 @@ struct sock *llc_lookup_established(struct llc_sap *sap, struct llc_addr *daddr,
         }
         rc = NULL;
 found:
-        read_unlock_bh(&sap->sk_list.lock);
+        read_unlock(&sap->sk_list.lock);
         return rc;
 }
 
+struct sock *llc_lookup_established(struct llc_sap *sap,
+                                    struct llc_addr *daddr,
+                                    struct llc_addr *laddr)
+{
+        struct sock *sk;
+
+        local_bh_disable();
+        sk = __llc_lookup_established(sap, daddr, laddr);
+        local_bh_enable();
+        return sk;
+}
+
 /**
  *      llc_lookup_listener - Finds listener for local MAC + SAP
  *      @sap: SAP
@@ -516,6 +529,7 @@ found:
  *      Search connection list of the SAP and finds connection listening on
  *      local mac, and local sap. Returns pointer for parent socket found,
  *      %NULL otherwise.
+ *      Caller has to make sure local_bh is disabled.
  */
 static struct sock *llc_lookup_listener(struct llc_sap *sap,
                                         struct llc_addr *laddr)
@@ -523,7 +537,7 @@ static struct sock *llc_lookup_listener(struct llc_sap *sap,
         struct sock *rc;
         struct hlist_node *node;
 
-        read_lock_bh(&sap->sk_list.lock);
+        read_lock(&sap->sk_list.lock);
         sk_for_each(rc, node, &sap->sk_list.list) {
                 struct llc_sock *llc = llc_sk(rc);
 
@@ -537,10 +551,19 @@ static struct sock *llc_lookup_listener(struct llc_sap *sap,
         }
         rc = NULL;
 found:
-        read_unlock_bh(&sap->sk_list.lock);
+        read_unlock(&sap->sk_list.lock);
         return rc;
 }
 
+static struct sock *__llc_lookup(struct llc_sap *sap,
+                                 struct llc_addr *daddr,
+                                 struct llc_addr *laddr)
+{
+        struct sock *sk = __llc_lookup_established(sap, daddr, laddr);
+
+        return sk ? : llc_lookup_listener(sap, laddr);
+}
+
 /**
  *      llc_data_accept_state - designates if in this state data can be sent.
  *      @state: state of connection.
@@ -666,15 +689,34 @@ void llc_sap_remove_socket(struct llc_sap *sap, struct sock *sk)
 static int llc_conn_rcv(struct sock* sk, struct sk_buff *skb)
 {
         struct llc_conn_state_ev *ev = llc_conn_ev(skb);
-        struct llc_sock *llc = llc_sk(sk);
 
-        if (!llc->dev)
-                llc->dev = skb->dev;
         ev->type   = LLC_CONN_EV_TYPE_PDU;
         ev->reason = 0;
         return llc_conn_state_process(sk, skb);
 }
 
+static struct sock *llc_create_incoming_sock(struct sock *sk,
+                                             struct net_device *dev,
+                                             struct llc_addr *saddr,
+                                             struct llc_addr *daddr)
+{
+        struct sock *newsk = llc_sk_alloc(sk->sk_family, GFP_ATOMIC,
+                                          sk->sk_prot);
+        struct llc_sock *newllc, *llc = llc_sk(sk);
+
+        if (!newsk)
+                goto out;
+        newllc = llc_sk(newsk);
+        memcpy(&newllc->laddr, daddr, sizeof(newllc->laddr));
+        memcpy(&newllc->daddr, saddr, sizeof(newllc->daddr));
+        newllc->dev = dev;
+        dev_hold(dev);
+        llc_sap_add_socket(llc->sap, newsk);
+        llc_sap_hold(llc->sap);
+out:
+        return newsk;
+}
+
 void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb)
 {
         struct llc_addr saddr, daddr;
@@ -685,34 +727,35 @@ void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb)
         llc_pdu_decode_da(skb, daddr.mac);
         llc_pdu_decode_dsap(skb, &daddr.lsap);
 
-        sk = llc_lookup_established(sap, &saddr, &daddr);
-        if (!sk) {
+        sk = __llc_lookup(sap, &saddr, &daddr);
+        if (!sk)
+                goto drop;
+
+        bh_lock_sock(sk);
+        /*
+         * This has to be done here and not at the upper layer ->accept
+         * method because of the way the PROCOM state machine works:
+         * it needs to set several state variables (see, for instance,
+         * llc_adm_actions_2 in net/llc/llc_c_st.c) and send a packet to
+         * the originator of the new connection, and this state has to be
+         * in the newly created struct sock private area. -acme
+         */
+        if (unlikely(sk->sk_state == TCP_LISTEN)) {
+                struct sock *newsk = llc_create_incoming_sock(sk, skb->dev,
+                                                              &saddr, &daddr);
+                if (!newsk)
+                        goto drop_unlock;
+                skb_set_owner_r(skb, newsk);
+        } else {
                 /*
-                 * Didn't find an active connection; verify if there
-                 * is a listening socket for this llc addr
+                 * Can't be skb_set_owner_r, this will be done at the
+                 * llc_conn_state_process function, later on, when we will use
+                 * skb_queue_rcv_skb to send it to upper layers, this is
+                 * another trick required to cope with how the PROCOM state
+                 * machine works. -acme
                  */
-                struct llc_sock *llc;
-                struct sock *parent = llc_lookup_listener(sap, &daddr);
-
-                if (!parent) {
-                        dprintk("llc_lookup_listener failed!\n");
-                        goto drop;
-                }
-
-                sk = llc_sk_alloc(parent->sk_family, GFP_ATOMIC, parent->sk_prot);
-                if (!sk) {
-                        sock_put(parent);
-                        goto drop;
-                }
-                llc = llc_sk(sk);
-                memcpy(&llc->laddr, &daddr, sizeof(llc->laddr));
-                memcpy(&llc->daddr, &saddr, sizeof(llc->daddr));
-                llc_sap_add_socket(sap, sk);
-                sock_hold(sk);
-                skb_set_owner_r(skb, parent);
-                sock_put(parent);
+                skb->sk = sk;
         }
-        bh_lock_sock(sk);
         if (!sock_owned_by_user(sk))
                 llc_conn_rcv(sk, skb);
         else {
@@ -720,11 +763,16 @@ void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb)
                 llc_set_backlog_type(skb, LLC_PACKET);
                 sk_add_backlog(sk, skb);
         }
+out:
         bh_unlock_sock(sk);
         sock_put(sk);
         return;
 drop:
         kfree_skb(skb);
+        return;
+drop_unlock:
+        kfree_skb(skb);
+        goto out;
 }
 
 #undef LLC_REFCNT_DEBUG