Track mbuf deallocation

Using unique_ptr and make sure we don't leak.
Note that the FreeBSD convention is to let the upper protocols to
free the mbuf in the receive path (without them increasing the ref count)

drivers/virtio-net.cc

@@ -184,10 +184,10 @@ namespace virtio {
     struct virtio_net_req {
         struct virtio_net::virtio_net_hdr hdr;
         sglist payload;
-        struct mbuf *m;
+        std::unique_ptr<struct mbuf> um;
 
-        virtio_net_req() :m(nullptr) {memset(&hdr,0,sizeof(hdr));};
-        ~virtio_net_req() {}
+        virtio_net_req() {memset(&hdr,0,sizeof(hdr));};
+        ~virtio_net_req() {if (um) m_freem(um.get());}
     };
 
     void virtio_net::receiver() {
@@ -207,11 +207,10 @@ namespace virtio {
                 auto ii = req->payload._nodes.begin();
                 ii++;
 
-                struct mbuf *m = req->m;
-
+                auto m = req->um.release();
                 u8* buf = mtod(m, u8*);
-
                 virtio_net_d(fmt("\t got hdr len:%d = %d, len= %d vaddr=%p") % i++ % (int)req->hdr.hdr_len % len % (void*)buf);
+                delete req;
 
                 m->m_pkthdr.len = len;
                 m->m_pkthdr.rcvif = _ifn;
@@ -220,9 +219,6 @@ namespace virtio {
 
                 _ifn->if_ipackets++;
                 (*_ifn->if_input)(_ifn, m);
-
-                delete req;
-                // TODO: who should free it? m_freem(m);
             }
 
             if (queue->avail_ring_has_room(queue->size()/2)) {
@@ -249,12 +245,11 @@ namespace virtio {
             struct mbuf *m = m_getjcl(M_NOWAIT, MT_DATA, M_PKTHDR, page_size);
             if (!m)
                 break;
+            req->um.reset(m);
 
-            req->m = m;
             u8 *mdata;
-            //int offset;
-
             mdata = mtod(m, u8*);
+
             //Better use the header withing the mbuf allocation like in freebsd
             //offset = 0;
             //struct virtio_net_hdr *hdr = static_cast<struct virtio_net_hdr*>(mdata);
@@ -265,7 +260,6 @@ namespace virtio {
 
             if (!queue->add_buf(&req->payload,0,req->payload.get_sgs(),req)) {
                 delete req;
-                m_freem(m);
                 break;
             }
         }
@@ -288,6 +282,7 @@ namespace virtio {
 
         //TODO: verify what the hdr_len should be
         req->hdr.hdr_len = ETH_ALEN;
+        req->um.reset(m);
         req->payload.add(mmu::virt_to_phys(static_cast<void*>(&req->hdr)), sizeof(struct virtio_net_hdr), true);
         // leak for now ; req->buffer = (u8*)out;
 
@@ -334,9 +329,7 @@ namespace virtio {
 
         while((req = static_cast<virtio_net_req*>(queue->get_buf(&len))) != nullptr) {
             virtio_net_d(fmt("%s: gc %d") % __FUNCTION__ % i++);
-
             delete req;
-            if (req->m) m_freem(req->m);
         }
     }