[tcp] Attempt to catch all possible error cases with debug messages

All TCP errors or unusual events should now generate a debugging
message at DBGLVL_LOG, with enough information (SEQ and ACK numbers)
to be able to identify the corresponding packet (or missing packet) in
a network trace from the remote end.

diff --git a/src/net/tcp.c b/src/net/tcp.c
index d9f6c2d..5a64c83 100644 (file)
--- a/src/net/tcp.c
+++ b/src/net/tcp.c
@@ -402,6 +402,7 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) {
        size_t seq_len;
        size_t app_win;
        size_t max_rcv_win;
+       int rc;
 
        /* If retransmission timer is already running, do nothing */
        if ( timer_running ( &tcp->timer ) )
@@ -438,7 +439,9 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) {
        /* Allocate I/O buffer */
        iobuf = alloc_iob ( len + MAX_HDR_LEN );
        if ( ! iobuf ) {
-               DBGC ( tcp, "TCP %p could not allocate data buffer\n", tcp );
+               DBGC ( tcp, "TCP %p could not allocate iobuf for %08x..%08x "
+                      "%08x\n", tcp, tcp->snd_seq, ( tcp->snd_seq + seq_len ),
+                      tcp->rcv_ack );
                return -ENOMEM;
        }
        iob_reserve ( iobuf, MAX_HDR_LEN );
@@ -495,8 +498,15 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) {
        DBGC2 ( tcp, "\n" );
 
        /* Transmit packet */
-       return tcpip_tx ( iobuf, &tcp_protocol, NULL, &tcp->peer, NULL,
-                         &tcphdr->csum );
+       if ( ( rc = tcpip_tx ( iobuf, &tcp_protocol, NULL, &tcp->peer, NULL,
+                              &tcphdr->csum ) ) != 0 ) {
+               DBGC ( tcp, "TCP %p could not transmit %08x..%08x %08x: %s\n",
+                      tcp, tcp->snd_seq, ( tcp->snd_seq + tcp->snd_sent ),
+                      tcp->rcv_ack, strerror ( rc ) );
+               return rc;
+       }
+
+       return 0;
 }
 
 /**
@@ -510,9 +520,9 @@ static void tcp_expired ( struct retry_timer *timer, int over ) {
                container_of ( timer, struct tcp_connection, timer );
        int graceful_close = TCP_CLOSED_GRACEFULLY ( tcp->tcp_state );
 
-       DBGC ( tcp, "TCP %p timer %s in %s for [%08x,%08x)\n", tcp,
+       DBGC ( tcp, "TCP %p timer %s in %s for %08x..%08x %08x\n", tcp,
               ( over ? "expired" : "fired" ), tcp_state ( tcp->tcp_state ),
-              tcp->snd_seq, ( tcp->snd_seq + tcp->snd_sent ) );
+              tcp->snd_seq, ( tcp->snd_seq + tcp->snd_sent ), tcp->rcv_ack );
 
        assert ( ( tcp->tcp_state == TCP_SYN_SENT ) ||
                 ( tcp->tcp_state == TCP_SYN_RCVD ) ||
@@ -547,11 +557,14 @@ static int tcp_xmit_reset ( struct tcp_connection *tcp,
                            struct tcp_header *in_tcphdr ) {
        struct io_buffer *iobuf;
        struct tcp_header *tcphdr;
+       int rc;
 
        /* Allocate space for dataless TX buffer */
        iobuf = alloc_iob ( MAX_HDR_LEN );
        if ( ! iobuf ) {
-               DBGC ( tcp, "TCP %p could not allocate data buffer\n", tcp );
+               DBGC ( tcp, "TCP %p could not allocate iobuf for RST "
+                      "%08x..%08x %08x\n", tcp, ntohl ( in_tcphdr->ack ),
+                      ntohl ( in_tcphdr->ack ), ntohl ( in_tcphdr->seq ) );
                return -ENOMEM;
        }
        iob_reserve ( iobuf, MAX_HDR_LEN );
@@ -577,8 +590,16 @@ static int tcp_xmit_reset ( struct tcp_connection *tcp,
        DBGC2 ( tcp, "\n" );
 
        /* Transmit packet */
-       return tcpip_tx ( iobuf, &tcp_protocol, NULL, st_dest,
-                         NULL, &tcphdr->csum );
+       if ( ( rc = tcpip_tx ( iobuf, &tcp_protocol, NULL, st_dest,
+                              NULL, &tcphdr->csum ) ) != 0 ) {
+               DBGC ( tcp, "TCP %p could not transmit RST %08x..%08x %08x: "
+                      "%s\n", tcp, ntohl ( in_tcphdr->ack ),
+                      ntohl ( in_tcphdr->ack ), ntohl ( in_tcphdr->seq ),
+                      strerror ( rc ) );
+               return rc;
+       }
+
+       return 0;
 }
 
 /***************************************************************************
@@ -728,8 +749,8 @@ static int tcp_rx_ack ( struct tcp_connection *tcp, uint32_t ack,
                 * timer running, as for the ack_len==0 case, to
                 * handle old duplicate ACKs.
                 */
-               DBGC ( tcp, "TCP %p received ACK for [%08x,%08zx), "
-                      "sent only [%08x,%08x)\n", tcp, tcp->snd_seq,
+               DBGC ( tcp, "TCP %p received ACK for %08x..%08zx, "
+                      "sent only %08x..%08x\n", tcp, tcp->snd_seq,
                       ( tcp->snd_seq + ack_len ), tcp->snd_seq,
                       ( tcp->snd_seq + tcp->snd_sent ) );
                /* Send RST if an out-of-range ACK is received on a
@@ -785,8 +806,11 @@ static int tcp_rx_data ( struct tcp_connection *tcp, uint32_t seq,
        len -= already_rcvd;
 
        /* Deliver data to application */
-       if ( ( rc = xfer_deliver_iob ( &tcp->xfer, iobuf ) ) != 0 )
+       if ( ( rc = xfer_deliver_iob ( &tcp->xfer, iobuf ) ) != 0 ) {
+               DBGC ( tcp, "TCP %p could not deliver %08x..%08x: %s\n",
+                      tcp, seq, ( seq + len ), strerror ( rc ) );
                return rc;
+       }
 
        /* Acknowledge new data */
        tcp_rx_seq ( tcp, len );
@@ -844,6 +868,7 @@ static int tcp_rx_rst ( struct tcp_connection *tcp, uint32_t seq ) {
        tcp_dump_state ( tcp );
        tcp_close ( tcp, -ECONNRESET );
 
+       DBGC ( tcp, "TCP %p connection reset by peer\n", tcp );
        return -ECONNRESET;
 }