11 files changed, 591 insertions, 82 deletions

diff --git a/Makefile b/Makefile
index 00a9f93..c7105d4 100644
--- a/Makefile
+++ b/Makefile
@@ -68,9 +68,9 @@ CFLAGS+=-I$(LIBOWFAT_HEADERS) -DGIT_VERSION=$(GIT_VERSION) -Wall -pipe -pthread
 LDFLAGS+=-L$(LIBOWFAT_LIBRARY) -lowfat -pthread
 
 BINARY =opentracker
-HEADERS=trackerlogic.h scan_urlencoded_query.h ot_buf.h ot_hex.h ot_ip.h ot_config.h ot_scan.h ot_socket.h ot_mutex.h ot_random.h ot_stats.h ot_vector.h ot_clean.h ot_udp.h ot_iovec.h ot_fullscrape.h ot_accesslist.h ot_http.h ot_livesync.h ot_rijndael.h
-SOURCES=opentracker.c trackerlogic.c scan_urlencoded_query.c ot_buf.c ot_hex.c ot_ip.c ot_config.c ot_scan.c ot_socket.c ot_mutex.c ot_random.c ot_stats.c ot_vector.c ot_clean.c ot_udp.c ot_iovec.c ot_fullscrape.c ot_accesslist.c ot_http.c ot_livesync.c ot_rijndael.c
-SOURCES_proxy=proxy.c ot_vector.c ot_mutex.c ot_random.c ot_scan.c ot_ip.c ot_socket.c
+HEADERS=trackerlogic.h scan_urlencoded_query.h ot_batch.h ot_buf.h ot_hex.h ot_ip.h ot_config.h ot_scan.h ot_socket.h ot_mutex.h ot_random.h ot_stats.h ot_vector.h ot_clean.h ot_udp.h ot_iovec.h ot_fullscrape.h ot_accesslist.h ot_http.h ot_livesync.h ot_rijndael.h
+SOURCES=opentracker.c trackerlogic.c scan_urlencoded_query.c ot_batch.c ot_buf.c ot_hex.c ot_ip.c ot_config.c ot_scan.c ot_socket.c ot_mutex.c ot_random.c ot_stats.c ot_vector.c ot_clean.c ot_udp.c ot_iovec.c ot_fullscrape.c ot_accesslist.c ot_http.c ot_livesync.c ot_rijndael.c
+SOURCES_proxy=proxy.c ot_batch.c ot_vector.c ot_mutex.c ot_random.c ot_scan.c ot_ip.c ot_socket.c
 
 OBJECTS = $(SOURCES:%.c=%.o)
 OBJECTS_debug = $(SOURCES:%.c=%.debug.o)
@@ -119,8 +119,8 @@ $(OBJECTS_proxy_debug): $(HEADERS)
 # has to. tests/stubs.c supplies the few symbols those modules reference but
 # the tests never reach.
 TESTBIN=tests/runner
-TEST_SOURCES=tests/runner.c tests/test.c tests/stubs.c tests/t_scan_urlencoded_query.c tests/t_iovec.c tests/t_vector.c tests/t_random.c tests/t_hex.c tests/t_accesslist.c tests/t_scan.c tests/t_buf.c tests/t_ip.c tests/t_socket.c tests/t_mutex.c
-TEST_UNITS=scan_urlencoded_query.c ot_buf.c ot_ip.c ot_socket.c ot_iovec.c ot_vector.c ot_random.c ot_hex.c ot_scan.c ot_accesslist.c ot_mutex.c
+TEST_SOURCES=tests/runner.c tests/test.c tests/stubs.c tests/t_scan_urlencoded_query.c tests/t_iovec.c tests/t_vector.c tests/t_random.c tests/t_hex.c tests/t_accesslist.c tests/t_scan.c tests/t_buf.c tests/t_ip.c tests/t_socket.c tests/t_mutex.c tests/t_batch.c
+TEST_UNITS=scan_urlencoded_query.c ot_batch.c ot_buf.c ot_ip.c ot_socket.c ot_iovec.c ot_vector.c ot_random.c ot_hex.c ot_scan.c ot_accesslist.c ot_mutex.c
 TEST_HEADERS=tests/test.h $(HEADERS)
 # Tests reach code that sits behind feature flags, so the units under test are
 # built with those features enabled. A test binary is not a production binary.
diff --git a/opentracker.c b/opentracker.c
index 96a265a..50fff29 100644
--- a/opentracker.c
+++ b/opentracker.c
@@ -23,7 +23,6 @@
 
 /* Libowfat */
 #include "io.h"
-#include "iob.h"
 
 /* Opentracker */
 #include "ot_accesslist.h"
@@ -120,9 +119,8 @@ static ssize_t header_complete(char *request, ssize_t byte_count) {
 static void handle_dead(const int64_t sock) {
   struct http_data *cookie = io_getcookie(sock);
   if (cookie) {
-    size_t i;
-    for (i = 0; i < cookie->batches; ++i)
-      iob_reset(cookie->batch + i);
+    if (cookie->batch)
+      batch_reset(cookie->batch);
     free(cookie->batch);
     buf_reset(&cookie->request);
     if (cookie->flag & (STRUCT_HTTP_FLAG_WAITINGFORTASK | STRUCT_HTTP_FLAG_CHUNKED_IN_TRANSFER))
@@ -178,33 +176,23 @@ static void handle_read(const int64_t sock, struct ot_workstruct *ws) {
 
 static void handle_write(const int64_t sock) {
   struct http_data *cookie = io_getcookie(sock);
-  size_t            i;
   int               chunked = 0;
 
-  /* Look for the first io_batch still containing bytes to write */
   if (cookie) {
     if (cookie->flag & STRUCT_HTTP_FLAG_CHUNKED_IN_TRANSFER)
       chunked = 1;
 
-    for (i = 0; i < cookie->batches; ++i) {
-      if (cookie->batch[i].bytesleft) {
-        int64_t res = iob_send(sock, cookie->batch + i);
-
-        if (res == -3) {
-          handle_dead(sock);
-          return;
-        }
-
-        if (!cookie->batch[i].bytesleft)
-          continue;
-
-        if (res == -1 || res > 0 || i < cookie->batches - 1)
-          return;
+    if (cookie->batch) {
+      if (batch_send(sock, cookie->batch) == BATCH_FAILED) {
+        handle_dead(sock);
+        return;
       }
+      if (batch_pending(cookie->batch))
+        return;
     }
   }
 
-  /* In a chunked transfer after all batches accumulated have been sent, wait for the next one */
+  /* In a chunked transfer, wait for the next piece once everything queued has gone out */
   if (chunked)
     io_dontwantwrite(sock);
   else
diff --git a/ot_batch.c b/ot_batch.c
new file mode 100644
index 0000000..84eb4a8
--- /dev/null
+++ b/ot_batch.c
@@ -0,0 +1,158 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+   It is considered beerware. Prost. Skol. Cheers or whatever.
+
+   $id$ */
+
+/* System */
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+/* Opentracker */
+#include "ot_batch.h"
+
+#ifndef IOV_MAX
+#define IOV_MAX 1024
+#endif
+
+#define OT_BATCH_MIN_ENTRIES 16
+
+static int batch_room_for(ot_batch *batch, size_t wanted) {
+  size_t        space = batch->space ? batch->space : OT_BATCH_MIN_ENTRIES;
+  struct iovec *grown;
+
+  if (batch->count + wanted <= batch->space)
+    return 0;
+
+  /* During a chunked transfer entries are appended while earlier ones are
+     still going out, so the front of the array frees up as we go. Slide the
+     rest down before asking for more. */
+  if (batch->first && batch->count - batch->first + wanted <= batch->space) {
+    memmove(batch->entries, batch->entries + batch->first, (batch->count - batch->first) * sizeof(struct iovec));
+    batch->count -= batch->first;
+    batch->first  = 0;
+    return 0;
+  }
+
+  while (space < batch->count + wanted)
+    space *= 2;
+
+  if (!(grown = realloc(batch->entries, space * sizeof(struct iovec))))
+    return -1;
+
+  batch->entries = grown;
+  batch->space   = space;
+  return 0;
+}
+
+int batch_add(ot_batch *batch, void *buf, size_t len) {
+  if (batch_room_for(batch, 1)) {
+    free(buf);
+    return -1;
+  }
+
+  batch->entries[batch->count].iov_base = buf;
+  batch->entries[batch->count].iov_len  = len;
+  ++batch->count;
+  return 0;
+}
+
+int batch_add_vector(ot_batch *batch, const struct iovec *entries, size_t count) {
+  if (batch_room_for(batch, count)) {
+    while (count--)
+      free(entries[count].iov_base);
+    return -1;
+  }
+
+  memcpy(batch->entries + batch->count, entries, count * sizeof(struct iovec));
+  batch->count += count;
+  return 0;
+}
+
+/* Drop everything the kernel accepted, freeing each buffer as it goes */
+static void batch_consume(ot_batch *batch, size_t written) {
+  while (written) {
+    struct iovec *entry = batch->entries + batch->first;
+    size_t        left  = entry->iov_len - batch->offset;
+
+    if (written < left) {
+      batch->offset += written;
+      return;
+    }
+
+    free(entry->iov_base);
+    written      -= left;
+    batch->offset = 0;
+    ++batch->first;
+  }
+
+  /* Nothing is outstanding, so the array can start over from the front */
+  if (batch->first == batch->count)
+    batch->first = batch->count = 0;
+}
+
+/* A peer that has gone away must come back as an error rather than as a
+   signal that kills the tracker, so ask the kernel not to raise one where it
+   can be asked. macOS cannot, and relies on SIGPIPE being blocked. */
+static ssize_t batch_writev(int s, struct iovec *entries, int count) {
+#ifdef MSG_NOSIGNAL
+  struct msghdr msg;
+
+  memset(&msg, 0, sizeof(msg));
+  msg.msg_iov    = entries;
+  msg.msg_iovlen = count;
+  return sendmsg(s, &msg, MSG_NOSIGNAL);
+#else
+  return writev(s, entries, count);
+#endif
+}
+
+ssize_t batch_send(int s, ot_batch *batch) {
+  size_t  entries = batch->count - batch->first;
+  ssize_t written;
+
+  if (!batch_pending(batch))
+    return BATCH_DONE;
+
+  if (entries > IOV_MAX)
+    entries = IOV_MAX;
+
+  /* The first entry may be half way out already */
+  batch->entries[batch->first].iov_base = (char *)batch->entries[batch->first].iov_base + batch->offset;
+  batch->entries[batch->first].iov_len -= batch->offset;
+  written                               = batch_writev(s, batch->entries + batch->first, (int)entries);
+  batch->entries[batch->first].iov_base = (char *)batch->entries[batch->first].iov_base - batch->offset;
+  batch->entries[batch->first].iov_len += batch->offset;
+
+  if (written < 0)
+    return (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) ? BATCH_AGAIN : BATCH_FAILED;
+  if (!written)
+    return BATCH_FAILED;
+
+  batch_consume(batch, (size_t)written);
+  return written;
+}
+
+void batch_reset(ot_batch *batch) {
+  while (batch->first < batch->count)
+    free(batch->entries[batch->first++].iov_base);
+
+  free(batch->entries);
+  batch->entries   = NULL;
+  batch->count = batch->first = batch->offset = batch->space = 0;
+}
+
+/* For the few constants the chunked encoding needs, which the batch frees
+   along with everything else */
+int batch_add_copy(ot_batch *batch, const void *buf, size_t len) {
+  void *copy = malloc(len);
+
+  if (!copy)
+    return -1;
+  memcpy(copy, buf, len);
+  return batch_add(batch, copy, len);
+}
diff --git a/ot_batch.h b/ot_batch.h
new file mode 100644
index 0000000..c855671
--- /dev/null
+++ b/ot_batch.h
@@ -0,0 +1,48 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+   It is considered beerware. Prost. Skol. Cheers or whatever.
+
+   $id$ */
+
+#ifndef OT_BATCH_H__
+#define OT_BATCH_H__
+
+#include <stddef.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+
+/* A queue of buffers on their way to one socket. The batch owns every buffer
+   handed to it and frees each one as soon as it has left, so a client that
+   reads slowly costs memory only for what it has not received yet.
+
+   A zeroed ot_batch is ready to use. */
+typedef struct {
+  struct iovec *entries;
+  size_t        space;
+  size_t        count;
+  size_t        first;  /* entries before this one are sent and freed */
+  size_t        offset; /* bytes of entries[first] already sent */
+} ot_batch;
+
+static inline int batch_pending(const ot_batch *batch) { return batch->first != batch->count; }
+
+/* What batch_send reports instead of a byte count */
+enum { BATCH_DONE = 0, BATCH_AGAIN = -1, BATCH_FAILED = -2 };
+
+/* Queue buf and take ownership of it. Returns 0, or -1 having freed buf. */
+int     batch_add(ot_batch *batch, void *buf, size_t len);
+
+/* Write as much as the socket takes. Returns the number of bytes written, or
+   BATCH_DONE, BATCH_AGAIN or BATCH_FAILED. */
+ssize_t batch_send(int s, ot_batch *batch);
+
+/* Queue every entry of a vector, taking ownership of each buffer but not of
+   the vector itself. Returns 0, or -1 having freed all of them. */
+int     batch_add_vector(ot_batch *batch, const struct iovec *entries, size_t count);
+
+/* Queue a copy of buf, which the batch then owns. Returns 0, or -1. */
+int     batch_add_copy(ot_batch *batch, const void *buf, size_t len);
+
+/* Free whatever has not left yet, along with the batch's own array */
+void    batch_reset(ot_batch *batch);
+
+#endif
diff --git a/ot_http.c b/ot_http.c
index 4c4121b..4675efb 100644
--- a/ot_http.c
+++ b/ot_http.c
@@ -15,7 +15,7 @@
 #include <unistd.h>
 
 /* Libowfat */
-#include "iob.h"
+#include "io.h"
 
 /* Opentracker */
 #include "ot_accesslist.h"
@@ -29,14 +29,7 @@
 #include "scan_urlencoded_query.h"
 #include "trackerlogic.h"
 
-#ifdef WANT_NO_AUTO_FREE
-#define OT_IOB_INIT(B) (bzero(B, sizeof(io_batch)), 0)
-#else
-#define OT_IOB_INIT(B) iob_init_autofree(B, 0)
-#endif
-
 #define OT_MAXMULTISCRAPE_COUNT 64
-#define OT_BATCH_LIMIT          (1024 * 1024 * 16)
 extern const char *g_redirecturl;
 
 const char  *g_stats_path;
@@ -90,20 +83,17 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
 
     memcpy(outbuf, ws->reply + written_size, ws->reply_size - written_size);
     if (!cookie->batch) {
-      cookie->batch = malloc(sizeof(io_batch));
-      if (!cookie->batch || OT_IOB_INIT(cookie->batch) == -1) {
-        free(cookie->batch);
+      cookie->batch = calloc(1, sizeof(ot_batch));
+      if (!cookie->batch) {
         free(outbuf);
         buf_reset(&cookie->request);
         free(cookie);
         io_close(sock);
         return;
       }
-
-      cookie->batches = 1;
     }
 
-    iob_addbuf_free(cookie->batch, outbuf, ws->reply_size - written_size);
+    batch_add(cookie->batch, outbuf, ws->reply_size - written_size);
 
     /* writeable short data sockets just have a tcp timeout */
     if (!ws->keep_alive) {
@@ -146,10 +136,9 @@ ssize_t http_issue_error(const int64_t sock, struct ot_workstruct *ws, int code)
 
 ssize_t http_sendiovecdata(const int64_t sock, struct ot_workstruct *ws, size_t iovec_entries, struct iovec *iovector, int is_partial) {
   struct http_data *cookie = io_getcookie(sock);
-  io_batch         *current;
   char             *header;
   const char       *encoding = "";
-  size_t            i, header_size, size = iovec_length(&iovec_entries, (const struct iovec **)&iovector);
+  size_t            header_size, size = iovec_length(&iovec_entries, (const struct iovec **)&iovector);
   tai6464           t;
 
   /* No cookie? Bad socket. Leave. */
@@ -199,42 +188,24 @@ ssize_t http_sendiovecdata(const int64_t sock, struct ot_workstruct *ws, size_t
     }
 
     if (!cookie->batch) {
-      cookie->batch = malloc(sizeof(io_batch));
-      if (!cookie->batch || OT_IOB_INIT(cookie->batch) == -1) {
-        free(cookie->batch);
+      cookie->batch = calloc(1, sizeof(ot_batch));
+      if (!cookie->batch) {
         free(header);
         iovec_free(&iovec_entries, &iovector);
         HTTPERROR_500;
       }
-      cookie->batches = 1;
     }
-    current = cookie->batch + cookie->batches - 1;
-    iob_addbuf_free(current, header, header_size);
-
-    /* Split huge iovectors into separate io_batches */
-    for (i = 0; i < (size_t)iovec_entries; ++i) {
-      /* If the current batch's limit is reached, try to reallocate a new batch to work on */
-      if (current->bytesleft > OT_BATCH_LIMIT) {
-        io_batch *new_batch = realloc(cookie->batch, (cookie->batches + 1) * sizeof(io_batch));
 
-        if (new_batch) {
-          cookie->batch = new_batch;
-          if (OT_IOB_INIT(cookie->batch + cookie->batches) != -1)
-            ++cookie->batches;
-        }
-        /* realloc may have moved the batches, so current is stale either way */
-        current = cookie->batch + cookie->batches - 1;
-      }
-      iob_addbuf_free(current, iovector[i].iov_base, iovector[i].iov_len);
-    }
+    batch_add(cookie->batch, header, header_size);
+    batch_add_vector(cookie->batch, iovector, iovec_entries);
     free(iovector);
+
     if (cookie->flag & STRUCT_HTTP_FLAG_CHUNKED_IN_TRANSFER)
-      iob_addbuf(current, "\r\n", 2);
+      batch_add_copy(cookie->batch, "\r\n", 2);
   }
 
   if ((cookie->flag & STRUCT_HTTP_FLAG_CHUNKED_IN_TRANSFER) && cookie->batch && !is_partial) {
-    current = cookie->batch + cookie->batches - 1;
-    iob_addbuf(current, "0\r\n\r\n", 5);
+    batch_add_copy(cookie->batch, "0\r\n\r\n", 5);
     cookie->flag &= ~STRUCT_HTTP_FLAG_CHUNKED_IN_TRANSFER;
   }
 
diff --git a/ot_http.h b/ot_http.h
index abad83a..003b545 100644
--- a/ot_http.h
+++ b/ot_http.h
@@ -10,9 +10,7 @@
 #include <sys/types.h>
 #include <sys/uio.h>
 
-/* Libowfat */
-#include "iob.h"
-
+#include "ot_batch.h"
 #include "ot_buf.h"
 #include "trackerlogic.h"
 
@@ -27,8 +25,7 @@ typedef enum {
 
 struct http_data {
   ot_buf           request;
-  io_batch        *batch;
-  size_t           batches;
+  ot_batch        *batch;
   ot_ip6           ip;
   STRUCT_HTTP_FLAG flag;
 };
diff --git a/proxy.c b/proxy.c
index 219d926..63b4c4f 100644
--- a/proxy.c
+++ b/proxy.c
@@ -16,9 +16,9 @@
 
 /* Libowfat */
 #include "io.h"
-#include "iob.h"
 
 /* Opentracker */
+#include "ot_batch.h"
 #include "ot_ip.h"
 #include "ot_mutex.h"
 #include "ot_random.h"
@@ -228,7 +228,7 @@ typedef struct {
   size_t   indata_length;     /* Length of unprocessed data */
   uint32_t tracker_id;        /* How the other end greeted */
   int64_t  fd;                /* A file handle, if connected, <= 0 is disconnected (0 initially, -1 else) */
-  io_batch outdata;           /* The iobatch containing our sync data */
+  ot_batch outdata;           /* The batch containing our sync data */
 
   size_t   packet_tcount;     /* Number of unprocessed torrents in packet we currently receive */
   uint8_t  packet_tprefix;    /* Prefix byte for all torrents in current packet */
@@ -243,7 +243,7 @@ void reset_info_block(proxy_peer *peer) {
   peer->tracker_id    = 0;
   peer->fd            = -1;
   peer->packet_tcount = 0;
-  iob_reset(&peer->outdata);
+  batch_reset(&peer->outdata);
   PROXYPEER_SETDISCONNECTED(peer->state);
 }
 
@@ -424,11 +424,11 @@ static void handle_write(int64_t peersocket) {
     }
     break;
   case FLAG_CONNECTED:
-    switch (iob_send(peersocket, &peer->outdata)) {
-    case 0: /* all data sent */
+    switch (batch_send(peersocket, &peer->outdata)) {
+    case BATCH_DONE:
       io_dontwantwrite(peersocket);
       break;
-    case -3: /* an error occured */
+    case BATCH_FAILED:
       io_close(peersocket);
       reset_info_block(peer);
       break;
@@ -728,7 +728,7 @@ static void *streamsync_worker(void *args) {
             void *tmp = malloc(mem);
             if (tmp) {
               memcpy(tmp, ptr, mem);
-              iob_addbuf_free(&g_connections[i].outdata, tmp, mem);
+              batch_add(&g_connections[i].outdata, tmp, mem);
               io_wantwrite(g_connections[i].fd);
             }
           }
diff --git a/tests/runner.c b/tests/runner.c
index 972a56a..148b928 100644
--- a/tests/runner.c
+++ b/tests/runner.c
@@ -24,6 +24,7 @@ static const struct module modules[] = {{"scan_urlencoded_query", test_scan_urle
                                         {"ot_ip", test_ip},
                                         {"ot_socket", test_socket},
                                         {"ot_mutex", test_mutex},
+                                        {"ot_batch", test_batch},
                                         {"ot_accesslist", test_accesslist},
                                         {NULL, NULL}};
 
diff --git a/tests/t_batch.c b/tests/t_batch.c
new file mode 100644
index 0000000..02743f1
--- /dev/null
+++ b/tests/t_batch.c
@@ -0,0 +1,348 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+   It is considered beerware. Prost. Skol. Cheers or whatever.
+
+   $id$ */
+
+/* System */
+#include <fcntl.h>
+#include <poll.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+/* Opentracker */
+#include "ot_batch.h"
+#include "test.h"
+
+/* The batch writes to a real socket pair, because what is worth pinning down
+   is what it does when the kernel takes only part of what it was offered. */
+
+static char *dup_of(const char *text) {
+  size_t len  = strlen(text);
+  char  *copy = malloc(len);
+
+  memcpy(copy, text, len);
+  return copy;
+}
+
+static void drain(int s, char *into, size_t len) {
+  size_t got = 0;
+
+  while (got < len) {
+    ssize_t r = read(s, into + got, len - got);
+
+    if (r <= 0)
+      break;
+    got += (size_t)r;
+  }
+  into[got] = 0;
+}
+
+static void case_queue_accounting(void) {
+  ot_batch batch;
+
+  memset(&batch, 0, sizeof(batch));
+
+  test_case("a zeroed batch is empty and sends nothing");
+  CHECK_INT(batch_pending(&batch), 0);
+  CHECK_INT(batch_send(-1, &batch), BATCH_DONE);
+
+  test_case("anything queued makes it pending");
+  CHECK_INT(batch_add(&batch, dup_of("hello "), 6), 0);
+  CHECK_INT(batch_add_copy(&batch, "world", 5), 0);
+  CHECK_INT(batch_pending(&batch), 1);
+  CHECK_INT(batch.count, 2);
+
+  batch_reset(&batch);
+  test_case("and a reset empties it");
+  CHECK_INT(batch_pending(&batch), 0);
+  CHECK_PTR(batch.entries, NULL);
+}
+
+static void case_send_in_one_go(void) {
+  ot_batch batch;
+  int      sv[2];
+  char     got[32];
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+
+  test_case("several buffers arrive as one stream, in order");
+  CHECK_INT(batch_add(&batch, dup_of("opentracker"), 11), 0);
+  CHECK_INT(batch_add_copy(&batch, " says ", 6), 0);
+  CHECK_INT(batch_add(&batch, dup_of("hello"), 5), 0);
+  CHECK_INT(batch_send(sv[0], &batch), 22);
+  CHECK_INT(batch_pending(&batch), 0);
+
+  drain(sv[1], got, 22);
+  CHECK_STR(got, "opentracker says hello");
+
+  test_case("and an empty batch reports it has nothing left");
+  CHECK_INT(batch_send(sv[0], &batch), BATCH_DONE);
+
+  batch_reset(&batch);
+  close(sv[0]);
+  close(sv[1]);
+}
+
+/* Send everything the batch holds, reading the other end as we go so the
+   socket never stays full, and return what arrived. */
+static size_t pump(int writer, int reader, ot_batch *batch, char *into, size_t room) {
+  size_t got = 0;
+
+  while (batch_pending(batch) || got < room) {
+    ssize_t r;
+
+    if (batch_pending(batch)) {
+      ssize_t res = batch_send(writer, batch);
+
+      if (res == BATCH_FAILED)
+        break;
+      if (res > 0)
+        continue;
+    }
+
+    r = read(reader, into + got, room - got);
+    if (r <= 0)
+      break;
+    got += (size_t)r;
+  }
+  return got;
+}
+
+static void case_partial_write_resumes(void) {
+  const size_t size = 200000;
+  ot_batch     batch;
+  int          sv[2], sndbuf = 4096;
+  char        *sent, *got;
+  size_t       i, arrived;
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+  setsockopt(sv[0], SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));
+  fcntl(sv[0], F_SETFL, fcntl(sv[0], F_GETFL, 0) | O_NONBLOCK);
+
+  sent = malloc(size);
+  got  = malloc(size);
+  for (i = 0; i < size; ++i)
+    sent[i] = (char)(i % 251);
+
+  test_case("a buffer the kernel takes in pieces arrives whole and in order");
+  CHECK_INT(batch_add(&batch, memcpy(malloc(size), sent, size), size), 0);
+  arrived = pump(sv[0], sv[1], &batch, got, size);
+  CHECK_INT(arrived, size);
+  CHECK_INT(batch_pending(&batch), 0);
+  CHECK_MEM(got, sent, size);
+
+  free(sent);
+  free(got);
+  batch_reset(&batch);
+  close(sv[0]);
+  close(sv[1]);
+}
+
+/* writev refuses more than IOV_MAX entries at once, so a long batch has to be
+   sent across several calls. */
+static void case_more_entries_than_one_writev(void) {
+  const size_t entries = 3000, each = 4;
+  ot_batch     batch;
+  int          sv[2], sndbuf = 4096;
+  char        *sent, *got;
+  size_t       i, arrived, refused = 0;
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+  setsockopt(sv[0], SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));
+  fcntl(sv[0], F_SETFL, fcntl(sv[0], F_GETFL, 0) | O_NONBLOCK);
+
+  sent = malloc(entries * each);
+  got  = malloc(entries * each);
+
+  test_case("a batch of more entries than writev accepts still arrives whole");
+  for (i = 0; i < entries; ++i) {
+    char piece[4];
+
+    piece[0] = (char)(i), piece[1] = (char)(i >> 8), piece[2] = 'x', piece[3] = 'y';
+    memcpy(sent + i * each, piece, each);
+    if (batch_add(&batch, memcpy(malloc(each), piece, each), each))
+      ++refused;
+  }
+  CHECK_INT(refused, 0);
+  CHECK_INT(batch.count, entries);
+
+  arrived = pump(sv[0], sv[1], &batch, got, entries * each);
+  CHECK_INT(arrived, entries * each);
+  CHECK_MEM(got, sent, entries * each);
+
+  free(sent);
+  free(got);
+  batch_reset(&batch);
+  close(sv[0]);
+  close(sv[1]);
+}
+
+static void case_reset_frees_the_unsent(void) {
+  ot_batch batch;
+  int      sv[2];
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+
+  test_case("a batch torn down mid flight keeps no bytes outstanding");
+  CHECK_INT(batch_add(&batch, dup_of("first"), 5), 0);
+  CHECK_INT(batch_add(&batch, dup_of("second"), 6), 0);
+  CHECK_INT(batch_send(sv[0], &batch), 11);
+  CHECK_INT(batch_add(&batch, dup_of("never sent"), 10), 0);
+  CHECK_INT(batch_pending(&batch), 1);
+
+  /* Whether the unsent buffer is freed is for the sanitizer to say */
+  batch_reset(&batch);
+  CHECK_INT(batch_pending(&batch), 0);
+  CHECK_INT(batch.count, 0);
+
+  close(sv[0]);
+  close(sv[1]);
+}
+
+static void case_closed_socket_is_fatal(void) {
+  ot_batch batch;
+  int      sv[2];
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+  close(sv[1]);
+
+  test_case("writing to a socket whose peer is gone reports a dead connection");
+  CHECK_INT(batch_add(&batch, dup_of("nobody is listening"), 19), 0);
+  CHECK_INT(batch_send(sv[0], &batch), BATCH_FAILED);
+
+  batch_reset(&batch);
+  close(sv[0]);
+}
+
+static void case_vector_is_taken_whole(void) {
+  ot_batch      batch;
+  struct iovec *vector = malloc(3 * sizeof(struct iovec));
+  int           sv[2];
+  char          got[32];
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+
+  test_case("a whole vector is queued in one go, in order");
+  vector[0].iov_base = dup_of("one "), vector[0].iov_len = 4;
+  vector[1].iov_base = dup_of("two "), vector[1].iov_len = 4;
+  vector[2].iov_base = dup_of("three"), vector[2].iov_len = 5;
+  CHECK_INT(batch_add_vector(&batch, vector, 3), 0);
+  free(vector);
+  CHECK_INT(batch.count, 3);
+  CHECK_INT(batch_send(sv[0], &batch), 13);
+
+  drain(sv[1], got, 13);
+  CHECK_STR(got, "one two three");
+
+  batch_reset(&batch);
+  close(sv[0]);
+  close(sv[1]);
+}
+
+/* The entry array starts small and doubles, so crossing that boundary one
+   buffer at a time is worth its own case. */
+static void case_growing_one_entry_at_a_time(void) {
+  const size_t entries = 100;
+  ot_batch     batch;
+  int          sv[2];
+  char         sent[400], got[401];
+  size_t       i, refused = 0;
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+
+  test_case("a batch grown one buffer at a time keeps them all, in order");
+  for (i = 0; i < entries; ++i) {
+    char piece[4];
+
+    piece[0] = (char)('a' + i % 26), piece[1] = (char)('0' + i % 10);
+    piece[2] = (char)('A' + i % 26), piece[3] = '.';
+    memcpy(sent + i * 4, piece, 4);
+    if (batch_add(&batch, memcpy(malloc(4), piece, 4), 4))
+      ++refused;
+  }
+  CHECK_INT(refused, 0);
+  CHECK_INT(batch.count, entries);
+  CHECK_INT(batch_send(sv[0], &batch), (ssize_t)(entries * 4));
+
+  drain(sv[1], got, entries * 4);
+  CHECK_MEM(got, sent, entries * 4);
+
+  batch_reset(&batch);
+  close(sv[0]);
+  close(sv[1]);
+}
+
+/* Appending while earlier entries are still on their way is what a chunked
+   transfer does. Rather than depend on when a kernel decides to block, this
+   takes entries off the front the way a completed send would and checks that
+   the array reuses the space instead of growing. */
+static void case_append_while_sending(void) {
+  const size_t per_round = 12, each = 8;
+  ot_batch     batch;
+  int          sv[2];
+  char         expected[16], got[17];
+  size_t       i, round, refused = 0, space_after_first = 0;
+
+  memset(&batch, 0, sizeof(batch));
+  CHECK_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+
+  test_case("an array whose front has gone out is reused, not grown");
+  for (round = 0; round < 8; ++round) {
+    for (i = 0; i < per_round; ++i) {
+      /* Distinct per entry, so a move from the wrong index shows up */
+      char *piece = malloc(each);
+
+      memset(piece, (int)('a' + (round * per_round + i) % 26), each);
+      piece[0] = (char)('0' + i);
+      piece[1] = (char)('0' + round);
+      if (batch_add(&batch, piece, each))
+        ++refused;
+    }
+
+    /* All but the last entry have left and been freed */
+    while (batch.count - batch.first > 1)
+      free(batch.entries[batch.first++].iov_base);
+
+    if (!round)
+      space_after_first = batch.space;
+  }
+  CHECK_INT(refused, 0);
+  CHECK_INT(batch.space, space_after_first);
+
+  test_case("and what is still queued survives the move, in order");
+  CHECK_INT(batch.count - batch.first, 1);
+  CHECK_INT(batch_add(&batch, memset(malloc(each), 'Z', each), each), 0);
+  CHECK_INT(batch_send(sv[0], &batch), (ssize_t)(2 * each));
+
+  memset(expected, (int)('a' + (7 * per_round + per_round - 1) % 26), each);
+  expected[0] = (char)('0' + per_round - 1);
+  expected[1] = '7';
+  memset(expected + each, 'Z', each);
+  drain(sv[1], got, 2 * each);
+  CHECK_MEM(got, expected, 2 * each);
+
+  batch_reset(&batch);
+  close(sv[0]);
+  close(sv[1]);
+}
+
+void test_batch(void) {
+  case_queue_accounting();
+  case_send_in_one_go();
+  case_vector_is_taken_whole();
+  case_growing_one_entry_at_a_time();
+  case_append_while_sending();
+  case_partial_write_resumes();
+  case_more_entries_than_one_writev();
+  case_reset_frees_the_unsent();
+  case_closed_socket_is_fatal();
+}
diff --git a/tests/test.h b/tests/test.h
index 9677524..fd574c2 100644
--- a/tests/test.h
+++ b/tests/test.h
@@ -87,5 +87,6 @@ void test_buf(void);
 void test_ip(void);
 void test_socket(void);
 void test_mutex(void);
+void test_batch(void);
 
 #endif
diff --git a/trackerlogic.c b/trackerlogic.c
index 0fa7bfb..74fea6d 100644
--- a/trackerlogic.c
+++ b/trackerlogic.c
@@ -10,9 +10,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-/* Libowfat */
-#include "io.h"
-#include "iob.h"
 
 /* Opentracker */
 #include "ot_accesslist.h"