tcp.h, opt.h, api.h, api_msg.h, tcp.c, tcp_in.c, api_lib.c, api_msg.c, sockets.c, init.c: task #7252: Implement TCP listen backlog: Warning: raw API applications have to call 'tcp_accepted(pcb)' in their accept callback to keep accepting new connections.

CHANGELOG

@@ -19,6 +19,12 @@ HISTORY
 
   ++ New features:
 
+  2007-12-21 Frédéric Bernon, Simon Goldschmidt, Jonathan Larmour
+  * tcp.h, opt.h, api.h, api_msg.h, tcp.c, tcp_in.c, api_lib.c, api_msg.c,
+    sockets.c, init.c: task #7252: Implement TCP listen backlog: Warning: raw API
+    applications have to call 'tcp_accepted(pcb)' in their accept callback to
+    keep accepting new connections.
+
   2007-12-13 Frédéric Bernon
   * api_msg.c, err.h, err.c, sockets.c, dns.c, dns.h: replace "enum dns_result"
     by err_t type. Add a new err_t code "ERR_INPROGRESS".

src/api/api_lib.c

@@ -261,16 +261,23 @@ netconn_disconnect(struct netconn *conn)
  * Set a TCP netconn into listen mode
  *
  * @param conn the tcp netconn to set to listen mode
+ * @param backlog the listen backlog (0 = max), only used if LWIP_LISTEN_BACKLOG==1
  * @return ERR_OK if the netconn was set to listen (UDP and RAW netconns
  *         don't return any error (yet?))
  */
 err_t
-netconn_listen(struct netconn *conn)
+netconn_listen_with_backlog(struct netconn *conn, u8_t backlog)
 {
   struct api_msg msg;
 
+  /* This does no harm. If LWIP_LISTEN_BACKLOG is off, backlog is unused. */
+  LWIP_UNUSED_ARG(backlog);
+
   LWIP_ERROR("netconn_listen: invalid conn", (conn != NULL), return ERR_ARG;);
 
+#if LWIP_LISTEN_BACKLOG
+  msg.msg.msg.lb.backlog = backlog;
+#endif /* LWIP_LISTEN_BACKLOG */
   msg.function = do_listen;
   msg.msg.conn = conn;
   TCPIP_APIMSG(&msg);
@@ -292,15 +299,26 @@ netconn_accept(struct netconn *conn)
   LWIP_ERROR("netconn_accept: invalid acceptmbox", (conn->acceptmbox != SYS_MBOX_NULL), return NULL;);
 
 #if LWIP_SO_RCVTIMEO
-  if (sys_arch_mbox_fetch(conn->acceptmbox, (void *)&newconn, conn->recv_timeout)==SYS_ARCH_TIMEOUT) {
+  if (sys_arch_mbox_fetch(conn->acceptmbox, (void *)&newconn, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
     newconn = NULL;
-  }
+  } else
 #else
   sys_arch_mbox_fetch(conn->acceptmbox, (void *)&newconn, 0);
 #endif /* LWIP_SO_RCVTIMEO*/
-
-  /* Register event with callback */
-  API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
+  {
+    /* Register event with callback */
+    API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
+
+#if LWIP_LISTEN_BACKLOG
+    if (newconn != NULL) {
+      /* Let the stack know that we have accepted the connection. */
+      struct api_msg msg;
+      msg.function = do_recv;
+      msg.msg.conn = conn;
+      TCPIP_APIMSG(&msg);
+    }
+#endif /* LWIP_LISTEN_BACKLOG */
+  }
 
   return newconn;
 }

src/api/api_msg.c

@@ -735,6 +735,9 @@ do_listen(struct api_msg_msg *msg)
             if (msg->conn->err == ERR_OK) {
               msg->conn->state = NETCONN_LISTEN;
               msg->conn->pcb.tcp = lpcb;
+#if LWIP_LISTEN_BACKLOG
+              tcp_backlog(lpcb, msg->msg.lb.backlog);
+#endif /* LWIP_LISTEN_BACKLOG */
               tcp_arg(msg->conn->pcb.tcp, msg->conn);
               tcp_accept(msg->conn->pcb.tcp, accept_function);
             }
@@ -800,7 +803,14 @@ do_recv(struct api_msg_msg *msg)
   if (!ERR_IS_FATAL(msg->conn->err)) {
     if (msg->conn->pcb.tcp != NULL) {
       if (msg->conn->type == NETCONN_TCP) {
-        tcp_recved(msg->conn->pcb.tcp, msg->msg.r.len);
+#if LWIP_LISTEN_BACKLOG
+        if (msg->conn->pcb.tcp->state == LISTEN) {
+          tcp_accepted(msg->conn->pcb.tcp);
+        } else
+#endif /* LWIP_LISTEN_BACKLOG */
+        {
+          tcp_recved(msg->conn->pcb.tcp, msg->msg.r.len);
+        }
       }
     }
   }

src/api/sockets.c

@@ -430,15 +430,15 @@ lwip_listen(int s, int backlog)
   struct lwip_socket *sock;
   err_t err;
 
-  /* This does no harm. If debugging is off, backlog is unused. */
-  LWIP_UNUSED_ARG(backlog);
-
   LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_listen(%d, backlog=%d)\n", s, backlog));
+  LWIP_ASSERT("backlog must be between 0 and 255", backlog > 0);
+  LWIP_ASSERT("backlog must be between 0 and 255", backlog <= 0xff);
+
   sock = get_socket(s);
   if (!sock)
     return -1;
 
-  err = netconn_listen(sock->conn);
+  err = netconn_listen_with_backlog(sock->conn, backlog);
 
   if (err != ERR_OK) {
     LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_listen(%d) failed, err=%d\n", s, err));

src/core/init.c

@@ -152,6 +152,10 @@
 #if (MEM_USE_POOLS && !MEMP_USE_CUSTOM_POOLS)
   #error "MEM_USE_POOLS requires custom pools (MEMP_USE_CUSTOM_POOLS) to be enabled in your lwipopts.h"
 #endif
+#if (LWIP_DEFAULT_LISTEN_BACKLOG < 0) || (LWIP_DEFAULT_LISTEN_BACKLOG > 255)
+  #error "LWIP_DEFAULT_LISTEN_BACKLOG must fit into an u8_t"
+#endif
+
 
 /* Compile-time checks for deprecated options.
  */

src/core/tcp.c

@@ -368,6 +368,10 @@ tcp_listen(struct tcp_pcb *pcb)
 #if LWIP_CALLBACK_API
   lpcb->accept = tcp_accept_null;
 #endif /* LWIP_CALLBACK_API */
+#if LWIP_LISTEN_BACKLOG
+  lpcb->accepts_pending = 0;
+  lpcb->backlog = LWIP_DEFAULT_LISTEN_BACKLOG;
+#endif /* LWIP_LISTEN_BACKLOG */
   TCP_REG(&tcp_listen_pcbs.listen_pcbs, lpcb);
   return (struct tcp_pcb *)lpcb;
 }

src/core/tcp_in.c

@@ -381,6 +381,11 @@ tcp_listen_input(struct tcp_pcb_listen *pcb)
       tcphdr->dest, tcphdr->src);
   } else if (flags & TCP_SYN) {
     LWIP_DEBUGF(TCP_DEBUG, ("TCP connection request %"U16_F" -> %"U16_F".\n", tcphdr->src, tcphdr->dest));
+#if LWIP_LISTEN_BACKLOG
+    if (pcb->accepts_pending >= pcb->backlog) {
+      return ERR_ABRT;
+    }
+#endif /* LWIP_LISTEN_BACKLOG */
     npcb = tcp_alloc(pcb->prio);
     /* If a new PCB could not be created (probably due to lack of memory),
        we don't do anything, but rely on the sender will retransmit the
@@ -390,6 +395,9 @@ tcp_listen_input(struct tcp_pcb_listen *pcb)
       TCP_STATS_INC(tcp.memerr);
       return ERR_MEM;
     }
+#if LWIP_LISTEN_BACKLOG
+    pcb->accepts_pending++;
+#endif /* LWIP_LISTEN_BACKLOG */
     /* Set up the new PCB. */
     ip_addr_set(&(npcb->local_ip), &(iphdr->dest));
     npcb->local_port = pcb->local_port;

src/include/lwip/api.h

@@ -179,7 +179,8 @@ err_t             netconn_connect (struct netconn *conn,
                                    struct ip_addr *addr,
                                    u16_t port);
 err_t             netconn_disconnect (struct netconn *conn);
-err_t             netconn_listen  (struct netconn *conn);
+err_t             netconn_listen_with_backlog(struct netconn *conn, u8_t backlog);
+#define netconn_listen(conn) netconn_listen_with_backlog(conn, LWIP_DEFAULT_LISTEN_BACKLOG);
 struct netconn *  netconn_accept  (struct netconn *conn);
 struct netbuf *   netconn_recv    (struct netconn *conn);
 err_t             netconn_sendto  (struct netconn *conn,

src/include/lwip/api_msg.h

@@ -93,6 +93,11 @@ struct api_msg_msg {
       enum netconn_igmp join_or_leave;
     } jl;
 #endif /* LWIP_IGMP */
+#if LWIP_LISTEN_BACKLOG
+    struct {
+      u8_t backlog;
+    } lb;
+#endif /* LWIP_LISTEN_BACKLOG */
   } msg;
 };
 

src/include/lwip/opt.h

@@ -728,6 +728,23 @@
 #define LWIP_CALLBACK_API               0
 #endif
 
+/**
+ * LWIP_LISTEN_BACKLOG: Enable the backlog option for tcp listen pcb.
+ */
+#ifndef LWIP_LISTEN_BACKLOG
+#define LWIP_LISTEN_BACKLOG             1
+#endif
+
+/**
+ * The maximum allowed backlog for TCP listen netconns.
+ * This backlog is used unless another is explicitly specified.
+ * 0xff is the maximum (u8_t).
+ */
+#ifndef LWIP_DEFAULT_LISTEN_BACKLOG
+#define LWIP_DEFAULT_LISTEN_BACKLOG     0xff
+#endif
+
+
 /*
    ----------------------------------
    ---------- Pbuf options ----------

src/include/lwip/tcp.h

@@ -79,6 +79,11 @@ void             tcp_err     (struct tcp_pcb *pcb,
 #define          tcp_mss(pcb)      ((pcb)->mss)
 #define          tcp_sndbuf(pcb)   ((pcb)->snd_buf)
 
+#if LWIP_LISTEN_BACKLOG
+#define          tcp_accepted(pcb)       (((struct tcp_pcb_listen *)(pcb))->accepts_pending--)
+#define          tcp_backlog(pcb, bklog) (((struct tcp_pcb_listen *)(pcb))->backlog = bklog)
+#endif /* LWIP_LISTEN_BACKLOG */
+
 void             tcp_recved  (struct tcp_pcb *pcb, u16_t len);
 err_t            tcp_bind    (struct tcp_pcb *pcb, struct ip_addr *ipaddr,
                               u16_t port);
@@ -412,6 +417,10 @@ struct tcp_pcb_listen {
    */
   err_t (* accept)(void *arg, struct tcp_pcb *newpcb, err_t err);
 #endif /* LWIP_CALLBACK_API */
+#if LWIP_LISTEN_BACKLOG
+  u8_t backlog;
+  u8_t accepts_pending;
+#endif /* LWIP_LISTEN_BACKLOG */
 };
 
 #if LWIP_EVENT_API