[Qemu-devel] [PULL 5/8] s390x/3270: 3270 data stream handling

[Cornelia Huck]

From: Jing Liu <address@hidden>

This introduces the input and output handlers for 3270 device, setting
up the data tunnel among guest kernel, qemu and the 3270 client.

After the client connected and TN3270 handshake done, signal the not-ready
to ready status by an unsolicited device-end interrupt, and then the 3270
data stream could be handled correctly between the channel and socket.
Multiple commands generated by "Reset" key on x3270 are not supported now,
just simply terminate the connection.

Signed-off-by: Jing Liu <address@hidden>
Signed-off-by: Yang Chen <address@hidden>
Reviewed-by: QingFeng Hao <address@hidden>
Reviewed-by: Dong Jia Shi <address@hidden>
Signed-off-by: Cornelia Huck <address@hidden>
---
 hw/char/terminal3270.c      | 180 ++++++++++++++++++++++++++++++++++++++++++++
 hw/s390x/3270-ccw.c         |  75 ++++++++++++++++++
 hw/s390x/css.c              |   3 +
 include/hw/s390x/3270-ccw.h |   9 +++
 4 files changed, 267 insertions(+)

diff --git a/hw/char/terminal3270.c b/hw/char/terminal3270.c
index bef3812c18..55eed5622a 100644
--- a/hw/char/terminal3270.c
+++ b/hw/char/terminal3270.c
@@ -12,16 +12,114 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "sysemu/char.h"
 #include "hw/s390x/3270-ccw.h"
 
+/* Enough spaces for different window sizes. */
+#define INPUT_BUFFER_SIZE  1000
+/*
+ * 1 for header, 1024*2 for datastream, 2 for tail
+ * Reserve enough spaces for telnet IAC escape.
+ */
+#define OUTPUT_BUFFER_SIZE 2051
+
 typedef struct Terminal3270 {
     EmulatedCcw3270Device cdev;
+    CharBackend chr;
+    uint8_t inv[INPUT_BUFFER_SIZE];
+    uint8_t outv[OUTPUT_BUFFER_SIZE];
+    int in_len;
+    int out_len;
+    bool handshake_done;
 } Terminal3270;
 
 #define TYPE_TERMINAL_3270 "x-terminal3270"
+#define TERMINAL_3270(obj) \
+        OBJECT_CHECK(Terminal3270, (obj), TYPE_TERMINAL_3270)
+
+static int terminal_can_read(void *opaque)
+{
+    Terminal3270 *t = opaque;
+
+    return INPUT_BUFFER_SIZE - t->in_len;
+}
+
+/*
+ * Protocol handshake done,
+ * signal guest by an unsolicited DE irq.
+ */
+static void TN3270_handshake_done(Terminal3270 *t)
+{
+    CcwDevice *ccw_dev = CCW_DEVICE(t);
+    SubchDev *sch = ccw_dev->sch;
+
+    t->handshake_done = true;
+    sch->curr_status.scsw.dstat = SCSW_DSTAT_DEVICE_END;
+    css_conditional_io_interrupt(sch);
+}
+
+/*
+ * Receive inbound data from socket.
+ * For data given to guest, drop the data boundary IAC, IAC_EOR.
+ * TODO:
+ * Using "Reset" key on x3270 may result multiple commands in one packet.
+ * This usually happens when the user meets a poor traffic of the network.
+ * As of now, for such case, we simply terminate the connection,
+ * and we should come back here later with a better solution.
+ */
+static void terminal_read(void *opaque, const uint8_t *buf, int size)
+{
+    Terminal3270 *t = opaque;
+    CcwDevice *ccw_dev = CCW_DEVICE(t);
+    SubchDev *sch = ccw_dev->sch;
+    int end;
+
+    assert(size <= (INPUT_BUFFER_SIZE - t->in_len));
+
+    memcpy(&t->inv[t->in_len], buf, size);
+    t->in_len += size;
+    if (t->in_len < 2) {
+        return;
+    }
+
+    if (!t->handshake_done) {
+        /*
+         * Receiving Terminal Type is the last step of handshake.
+         * The data format: IAC SB Terminal-Type IS <terminal type> IAC SE
+         * The code for Terminal-Type is 0x18, for IS is 0.
+         * Simply check the data format and mark handshake_done.
+         */
+        if (t->in_len > 6 && t->inv[2] == 0x18 && t->inv[3] == 0x0 &&
+            t->inv[t->in_len - 2] == IAC && t->inv[t->in_len - 1] == IAC_SE) {
+            TN3270_handshake_done(t);
+            t->in_len = 0;
+        }
+        return;
+    }
+
+    for (end = 0; end < t->in_len - 1; end++) {
+        if (t->inv[end] == IAC && t->inv[end + 1] == IAC_EOR) {
+            break;
+        }
+    }
+    if (end == t->in_len - 2) {
+        /* Data is valid for consuming. */
+        t->in_len -= 2;
+        sch->curr_status.scsw.dstat = SCSW_DSTAT_ATTENTION;
+        css_conditional_io_interrupt(sch);
+    } else if (end < t->in_len - 2) {
+        /* "Reset" key is used. */
+        qemu_chr_fe_disconnect(&t->chr);
+    } else {
+        /* Gathering data. */
+        return;
+    }
+}
 
 static void terminal_init(EmulatedCcw3270Device *dev, Error **errp)
 {
+    Terminal3270 *t = TERMINAL_3270(dev);
     static bool terminal_available;
 
     if (terminal_available) {
@@ -29,13 +127,95 @@ static void terminal_init(EmulatedCcw3270Device *dev, 
Error **errp)
         return;
     }
     terminal_available = true;
+    qemu_chr_fe_set_handlers(&t->chr, terminal_can_read,
+                             terminal_read, NULL, t, NULL, true);
+}
+
+static int read_payload_3270(EmulatedCcw3270Device *dev, uint32_t cda,
+                             uint16_t count)
+{
+    Terminal3270 *t = TERMINAL_3270(dev);
+    int len;
+
+    len = MIN(count, t->in_len);
+    cpu_physical_memory_write(cda, t->inv, len);
+    t->in_len -= len;
+
+    return len;
+}
+
+/* TN3270 uses binary transmission, which needs escape IAC to IAC IAC */
+static int insert_IAC_escape_char(uint8_t *outv, int out_len)
+{
+    int IAC_num = 0, new_out_len, i, j;
+
+    for (i = 0; i < out_len; i++) {
+        if (outv[i] == IAC) {
+            IAC_num++;
+        }
+    }
+    if (IAC_num == 0) {
+        return out_len;
+    }
+    new_out_len = out_len + IAC_num;
+    for (i = out_len - 1, j = new_out_len - 1; j > i && i >= 0; i--, j--) {
+        outv[j] = outv[i];
+        if (outv[i] == IAC) {
+            outv[--j] = IAC;
+        }
+    }
+    return new_out_len;
 }
 
+/*
+ * Write 3270 outbound to socket.
+ * Return the count of 3270 data field if succeeded, zero if failed.
+ */
+static int write_payload_3270(EmulatedCcw3270Device *dev, uint8_t cmd,
+                              uint32_t cda, uint16_t count)
+{
+    Terminal3270 *t = TERMINAL_3270(dev);
+    int retval = 0;
+
+    assert(count <= (OUTPUT_BUFFER_SIZE - 3) / 2);
+
+    if (!t->handshake_done) {
+        /*
+         * Before having finished 3270 negotiation,
+         * sending outbound data is prohibited.
+         */
+        return 0;
+    }
+    if (!qemu_chr_fe_get_driver(&t->chr)) {
+        /* We just say we consumed all data if there's no backend. */
+        return count;
+    }
+    t->outv[0] = cmd;
+    cpu_physical_memory_read(cda, &t->outv[1], count);
+    t->out_len = count + 1;
+
+    t->out_len = insert_IAC_escape_char(t->outv, t->out_len);
+    t->outv[t->out_len++] = IAC;
+    t->outv[t->out_len++] = IAC_EOR;
+
+    retval = qemu_chr_fe_write_all(&t->chr, t->outv, t->out_len);
+    return (retval <= 0) ? 0 : (retval - 3);
+}
+
+static Property terminal_properties[] = {
+    DEFINE_PROP_CHR("chardev", Terminal3270, chr),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void terminal_class_init(ObjectClass *klass, void *data)
 {
+    DeviceClass *dc = DEVICE_CLASS(klass);
     EmulatedCcw3270Class *ck = EMULATED_CCW_3270_CLASS(klass);
 
+    dc->props = terminal_properties;
     ck->init = terminal_init;
+    ck->read_payload_3270 = read_payload_3270;
+    ck->write_payload_3270 = write_payload_3270;
 }
 
 static const TypeInfo ccw_terminal_info = {
diff --git a/hw/s390x/3270-ccw.c b/hw/s390x/3270-ccw.c
index 47b9e89bb7..a7a5b412e4 100644
--- a/hw/s390x/3270-ccw.c
+++ b/hw/s390x/3270-ccw.c
@@ -17,6 +17,80 @@
 #include "hw/s390x/css-bridge.h"
 #include "hw/s390x/3270-ccw.h"
 
+/* Handle READ ccw commands from guest */
+static int handle_payload_3270_read(EmulatedCcw3270Device *dev, CCW1 *ccw)
+{
+    EmulatedCcw3270Class *ck = EMULATED_CCW_3270_GET_CLASS(dev);
+    CcwDevice *ccw_dev = CCW_DEVICE(dev);
+    int len;
+
+    if (!ccw->cda) {
+        return -EFAULT;
+    }
+
+    len = ck->read_payload_3270(dev, ccw->cda, ccw->count);
+    ccw_dev->sch->curr_status.scsw.count = ccw->count - len;
+
+    return 0;
+}
+
+/* Handle WRITE ccw commands to write data to client */
+static int handle_payload_3270_write(EmulatedCcw3270Device *dev, CCW1 *ccw)
+{
+    EmulatedCcw3270Class *ck = EMULATED_CCW_3270_GET_CLASS(dev);
+    CcwDevice *ccw_dev = CCW_DEVICE(dev);
+    int len;
+
+    if (!ccw->cda) {
+        return -EFAULT;
+    }
+
+    len = ck->write_payload_3270(dev, ccw->cmd_code, ccw->cda, ccw->count);
+
+    if (len <= 0) {
+        return -EIO;
+    }
+
+    ccw_dev->sch->curr_status.scsw.count = ccw->count - len;
+    return 0;
+}
+
+static int emulated_ccw_3270_cb(SubchDev *sch, CCW1 ccw)
+{
+    int rc = 0;
+    EmulatedCcw3270Device *dev = sch->driver_data;
+
+    switch (ccw.cmd_code) {
+    case TC_WRITESF:
+    case TC_WRITE:
+    case TC_EWRITE:
+    case TC_EWRITEA:
+        rc = handle_payload_3270_write(dev, &ccw);
+        break;
+    case TC_RDBUF:
+    case TC_READMOD:
+        rc = handle_payload_3270_read(dev, &ccw);
+        break;
+    default:
+        rc = -ENOSYS;
+        break;
+    }
+
+    if (rc == -EIO) {
+        /* I/O error, specific devices generate specific conditions */
+        SCSW *s = &sch->curr_status.scsw;
+
+        sch->curr_status.scsw.dstat = SCSW_DSTAT_UNIT_CHECK;
+        sch->sense_data[0] = 0x40;    /* intervention-req */
+        s->ctrl &= ~SCSW_ACTL_START_PEND;
+        s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+        s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
+                   SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
+    }
+
+    return rc;
+}
+
 static void emulated_ccw_3270_realize(DeviceState *ds, Error **errp)
 {
     uint16_t chpid;
@@ -48,6 +122,7 @@ static void emulated_ccw_3270_realize(DeviceState *ds, Error 
**errp)
     sch->id.cu_type = EMULATED_CCW_3270_CU_TYPE;
     css_sch_build_virtual_schib(sch, (uint8_t)chpid,
                                 EMULATED_CCW_3270_CHPID_TYPE);
+    sch->ccw_cb = emulated_ccw_3270_cb;
 
     ck->init(dev, &err);
     if (err) {
diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index d94498a97b..15c4f4b249 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -576,6 +576,9 @@ static void sch_handle_start_func(SubchDev *sch, ORB *orb)
             s->dstat = SCSW_DSTAT_CHANNEL_END | SCSW_DSTAT_DEVICE_END;
             s->cpa = sch->channel_prog + 8;
             break;
+        case -EIO:
+            /* I/O errors, status depends on specific devices */
+            break;
         case -ENOSYS:
             /* unsupported command, generate unit check (command reject) */
             s->ctrl &= ~SCSW_ACTL_START_PEND;
diff --git a/include/hw/s390x/3270-ccw.h b/include/hw/s390x/3270-ccw.h
index 45ea515e9f..46bee2533c 100644
--- a/include/hw/s390x/3270-ccw.h
+++ b/include/hw/s390x/3270-ccw.h
@@ -21,6 +21,15 @@
 #define EMULATED_CCW_3270_CHPID_TYPE 0x1a
 
 #define TYPE_EMULATED_CCW_3270 "emulated-ccw-3270"
+
+/* Local Channel Commands */
+#define TC_WRITE   0x01         /* Write */
+#define TC_RDBUF   0x02         /* Read buffer */
+#define TC_EWRITE  0x05         /* Erase write */
+#define TC_READMOD 0x06         /* Read modified */
+#define TC_EWRITEA 0x0d         /* Erase write alternate */
+#define TC_WRITESF 0x11         /* Write structured field */
+
 #define EMULATED_CCW_3270(obj) \
      OBJECT_CHECK(EmulatedCcw3270Device, (obj), TYPE_EMULATED_CCW_3270)
 #define EMULATED_CCW_3270_CLASS(klass) \
-- 
2.11.0