[Qemu-devel] [RFC PATCH v4 14/15] slirp: handle race condition

[Liu Ping Fan <qemulist@gmail.com>]

From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>

Slirp and its peer can run on different context at the same time.
Using lock to protect

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
 slirp/slirp.c |   16 ++++++++++++++--
 slirp/slirp.h |    3 +++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/slirp/slirp.c b/slirp/slirp.c
index 883b7bd..6bfcc67 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -206,6 +206,7 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
 
     slirp_init_once();
 
+    qemu_mutex_init(&slirp->lock);
     slirp->restricted = restricted;
 
     if_init(slirp);
@@ -248,6 +249,7 @@ void slirp_cleanup(Slirp *slirp)
 
     ip_cleanup(slirp);
     m_cleanup(slirp);
+    qemu_mutex_destroy(&slirp->lock);
 
     g_free(slirp->vdnssearch);
     g_free(slirp->tftp_prefix);
@@ -411,6 +413,7 @@ gboolean slirp_handler(gpointer data)
     struct socket *so, *so_next;
     int ret;
 
+    qemu_mutex_lock(&slirp->lock);
     /*
      * See if anything has timed out
      */
@@ -594,6 +597,7 @@ gboolean slirp_handler(gpointer data)
     }
 
     if_start(slirp);
+    qemu_mutex_unlock(&slirp->lock);
     return true;
 }
 
@@ -665,6 +669,7 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         return;
 
     proto = ntohs(*(uint16_t *)(pkt + 12));
+    qemu_mutex_lock(&slirp->lock);
     switch(proto) {
     case ETH_P_ARP:
         arp_input(slirp, pkt, pkt_len);
@@ -688,6 +693,7 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
     default:
         break;
     }
+    qemu_mutex_unlock(&slirp->lock);
 }
 
 /* Output the IP packet to the ethernet device. Returns 0 if the packet must be
@@ -860,15 +866,21 @@ void slirp_socket_recv(Slirp *slirp, struct in_addr guest_addr, int guest_port,
                        const uint8_t *buf, int size)
 {
     int ret;
-    struct socket *so = slirp_find_ctl_socket(slirp, guest_addr, guest_port);
+    struct socket *so;
+
+    qemu_mutex_lock(&slirp->lock);
+    so = slirp_find_ctl_socket(slirp, guest_addr, guest_port);
 
-    if (!so)
+    if (!so) {
+        qemu_mutex_unlock(&slirp->lock);
         return;
+    }
 
     ret = soreadbuf(so, (const char *)buf, size);
 
     if (ret > 0)
         tcp_output(sototcpcb(so));
+    qemu_mutex_unlock(&slirp->lock);
 }
 
 static void slirp_tcp_save(QEMUFile *f, struct tcpcb *tp)
diff --git a/slirp/slirp.h b/slirp/slirp.h
index 008360e..7ab0c70 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -135,6 +135,7 @@ void free(void *ptr);
 
 #include "qemu/queue.h"
 #include "qemu/sockets.h"
+#include "qemu/thread.h"
 
 #include "libslirp.h"
 #include "ip.h"
@@ -207,6 +208,8 @@ struct Slirp {
     u_int last_slowtimo;
     int do_slowtimo;
 
+    /* lock to protect slirp running both on frontend or SlirpState context */
+    QemuMutex lock;
     /* virtual network configuration */
     struct in_addr vnetwork_addr;
     struct in_addr vnetwork_mask;
-- 
1.7.4.4