[lwip-users] BUG: TCP loop forever with tcp_slowtmr

[cpp.china]

 Hello everybody!

 I am using lwip 1.1.0 and with the latest patchs from CVS, my system runs
uCos-II(every time tick is 10ms), ARM7(with 256Kbytes SRAM).

 If I use wait 100ms every time after lwip_read(1k), lwip will work much
stable. at this condition the lwip can transfer about 90 Mbytes(speed
at 10Kbytes/sec), about worked 8 hours, and pings can get replys.

 If I do not wait 100ms every time lwip_read(1k), the sending speed will
raise to 25k bytes/sec (why the speed is so slow?), at this condition
lwip will run into a forever loop processing tcp_slowtmr after transfered
about 1~6M bytes, it seem lwip crashed, and then no ping packet can be
replied, and application blocking in lwip_send.

 So I print the tcp_pcb content in tcp_slowtmr, and I found that
when lwip not work, the tcp_pcb->flags will be zero, I had also
tried to increase pcb_remove, but the system will soon crashed after
TCP transfered in serveral seconds.

  Here is the output message when lwip go into the forever loop in the
function tcp_slowtmr:

-------------------------------------------------------------------------------
 ------ PCB (0x15810) -----
 pcb->next           = 0x0            /* TCP state */
 pcb->state          = 0x00000004     /* ESTABLISHED */
 pcb->prio           = 0x00000040
 pcb->callback_arg   = 0x17110
 pcb->local_port     = 0x0000270f
 pcb->remote_port    = 0x00000e2e
 pcb->flags          = 0x00000000     /* Unknow */
<<<========================= HERE
 pcb->rcv_nxt        = 0xac7818f1
 pcb->rcv_wnd        = 0x00002000
 pcb->tmr            = 0x00000000
 pcb->polltmr        = 0x00000000
 pcb->pollinterval   = 0x00000004
 pcb->rtime          = 0x00000000     /* Retransmission timer. */
 pcb->mss            = 0x00000400     /* maximum segment size */
 pcb->rttest         = 0x00000000     /* RTT estimate in 500ms ticks */
 pcb->rtseq          = 0x00170b6f     /* sequence number being timed */
 pcb->rto            = 0x00000006     /* retransmission time-out */
 pcb->nrtx           = 0x00000000     /* number of retransmissions */
 pcb->lastack        = 0x00170b6f     /* Highest acknowledged seqno. */
 pcb->dupacks        = 0x00000000
 pcb->cwnd           = 0x0000fffc
 pcb->ssthresh       = 0x00004000
 pcb->snd_nxt        = 0x00170c6f     /* next seqno to be sent */
 pcb->snd_max        = 0x00170c6f     /* Highest seqno sent. */
 pcb->snd_wnd        = 0x00004000     /* sender window */
 pcb->snd_wl1        = 0xac7818f1     /* Sequence and
acknowledgement numbers of last window update. */
 pcb->snd_wl2        = 0x00170b6f
 pcb->snd_lbb        = 0x00170c6f     /* Sequence number of next
byte to be buffered. */
 pcb->acked          = 0x00000200
 pcb->snd_buf        = 0x00000700     /* Available buffer space for
sending (in bytes). */
 pcb->snd_queuelen   = 0x00000001     /* Available buffer space for
sending (in tcp_segs). */
 pcb->unsent         = 0x0            /* Unsent (queued) segments. */
 pcb->unacked        = 0x16e08        /* Sent but unacknowledged segments. */
 pcb->keepalive      = 0x006ddd00     /* idle time before KEEPALIVE is sent */
 pcb->keep_cnt       = 0x00000000     /* KEEPALIVE counter */
-------------------------------------------------------------------------------

  Here is part of my application code:
-------------------------------------------------------------------------------
  printf("tcp_client recv starting...\n");
  while (1) {
      len = lwip_read(clientfd, buf, sizeof(buf));
      if (len > 0) {
          send_try = 0;
      resend:
          if (send_try > 100) {
              printf("*** send failed!\n");
              break;
          }
          if (lwip_write(clientfd, buf, len) <= 0) {
              OSTimeDly(1);
              send_try++;
              goto resend;
          }
      }
      else if (len <= 0) {
          kprintf("<----- lwip_read() <= 0\n");
          break;
      }
      // if I comment the below line, lwip will soon crashed in serveral minites
      // if I use OSTimeDly(10) every loop, lwip seems more stable.
      //OSTimeDly(10);             <======================== HERE
  }

Here is my lwip config file: lwipopt.h
-------------------------------------------------------------------------------
#define MEM_SIZE                (1024 * 64)
#define MEMP_NUM_PBUF           32
#define MEMP_NUM_UDP_PCB        6
#define MEMP_NUM_TCP_PCB        10
#define MEMP_NUM_TCP_PCB_LISTEN 100
#define MEMP_NUM_NETBUF         16
#define MEMP_NUM_NETCONN        16
#define MEMP_NUM_API_MSG        32
#define MEMP_NUM_TCPIP_MSG      128
#define MEMP_NUM_SYS_TIMEOUT    6
#define PBUF_POOL_SIZE          256
#define PBUF_POOL_BUFSIZE       128
#define PBUF_LINK_HLEN          16
#define LWIP_TCP                1
#define TCP_TTL                 255
#define TCP_QUEUE_OOSEQ         0
#define TCP_MSS                 1024
#define TCP_SND_BUF             (1024 * 2)
#define TCP_SND_QUEUELEN        (4 * TCP_SND_BUF/TCP_MSS)
#define TCP_WND                 (1024 * 8)
#define TCP_MAXRTX              12
#define TCP_SYNMAXRTX           4
#define ARP_TABLE_SIZE          10
#define ARP_QUEUEING            0
#define IP_FORWARD              0
#define IP_OPTIONS              1
#define IP_REASSEMBLY           1
#define IP_FRAG                 1
#define ICMP_TTL                255
#define LWIP_DHCP               0
#define DHCP_USE_API            0
#define DHCP_DOES_ARP_CHECK     0
#define LWIP_UDP                1
#define UDP_TTL                 255
#define SYS_LIGHTWEIGHT_PROT    1
-------------------------------------------------------------------------------
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