#include "platform.h"
#include "gnunet-service-fs.h"
#include "gnunet-service-fs_cp.h"
+#include "gnunet-service-fs_push.h"
/**
* How often do we flush trust values to disk?
*/
struct GNUNET_TIME_Absolute last_migration_block;
+ /**
+ * Task scheduled to revive migration to this peer.
+ */
+ struct GNUNET_SCHEDULER_TaskIdentifier mig_revive_task;
+
/**
* Messages (replies, queries, content migration) we would like to
* send to this peer in the near future. Sorted by priority, head.
*/
struct GNUNET_CONTAINER_MulitHashMap *request_map;
- /**
- * ID of delay task for scheduling transmission.
- */
- GNUNET_SCHEDULER_TaskIdentifier delayed_transmission_request_task; // FIXME: used in 'push' (ugh!)
-
/**
* Increase in traffic preference still to be submitted
* to the core service for this peer.
*/
uint32_t disk_trust;
- /**
- * The peer's identity.
- */
- GNUNET_PEER_Id pid;
-
/**
* Which offset in "last_p2p_replies" will be updated next?
* (we go round-robin).
cp = GNUNET_malloc (sizeof (struct GSF_ConnectedPeer));
cp->transmission_delay = GNUNET_LOAD_value_init (latency);
- cp->pid = GNUNET_PEER_intern (peer);
+ cp->ppd.pid = GNUNET_PEER_intern (peer);
cp->transmission_delay = GNUNET_LOAD_value_init (0);
cp->irc = GNUNET_CORE_peer_change_preference (core,
peer,
GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
update_atsi (cp, atsi);
GSF_plan_notify_new_peer_ (cp);
+ GSF_push_start_ (cp);
return cp;
}
+/**
+ * It may be time to re-start migrating content to this
+ * peer. Check, and if so, restart migration.
+ *
+ * @param cls the 'struct GSF_ConnectedPeer'
+ * @param tc scheduler context
+ */
+static void
+revive_migration (void *cls,
+ const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+ struct GSF_ConnectedPeer *cp = cls;
+ struct GNUNET_TIME_Relative bt;
+
+ cp->mig_revive_task = GNUNET_SCHEDULER_NO_TASK;
+ bt = GNUNET_TIME_absolute_get_remaining (cp->ppd.migration_blocked_until);
+ if (0 != bt.rel_value)
+ {
+ /* still time left... */
+ cp->mig_revive_task
+ = GNUNET_SCHEDULER_add_delayed (bt,
+ &revive_migration,
+ cp);
+ return;
+ }
+ GSF_push_start_ (cp);
+}
+
+
/**
* Handle P2P "MIGRATION_STOP" message.
*
{
struct GSF_ConnectedPeer *cp;
const struct MigrationStopMessage *msm;
+ struct GNUNET_TIME_Relative bt;
msm = (const struct MigrationStopMessage*) message;
cp = GNUNET_CONTAINER_multihashmap_get (cp_map,
GNUNET_break (0);
return GNUNET_OK;
}
- cp->ppd.migration_blocked_until = GNUNET_TIME_relative_to_absolute (GNUNET_TIME_relative_ntoh (msm->duration));
+ bt = GNUNET_TIME_relative_ntoh (msm->duration);
+ cp->ppd.migration_blocked_until = GNUNET_TIME_relative_to_absolute (bt);
+ if (cp->mig_revive_task == GNUNET_SCHEDULER_NO_TASK)
+ {
+ GSF_push_stop_ (cp);
+ cp->mig_revive_task
+ = GNUNET_SCHEDULER_add_delayed (bt,
+ &revive_migration,
+ cp);
+ }
update_atsi (cp, atsi);
return GNUNET_OK;
}
cp->pth_tail,
prev,
pth);
- GNUNET_PEER_resolve (cp->pid,
+ GNUNET_PEER_resolve (cp->ppd.pid,
&target);
if (GNUNET_YES == is_query)
{
const struct GSF_ConnectedPeer *initiator_peer)
{
GNUNET_PEER_change_rc (cp->ppd.last_p2p_replies[cp->last_p2p_replies_woff % P2P_SUCCESS_LIST_SIZE], -1);
- cp->ppd.last_p2p_replies[cp->last_p2p_replies_woff++ % P2P_SUCCESS_LIST_SIZE] = initiator_peer->pid;
- GNUNET_PEER_change_rc (initiator_peer->pid, 1);
+ cp->ppd.last_p2p_replies[cp->last_p2p_replies_woff++ % P2P_SUCCESS_LIST_SIZE] = initiator_peer->ppd.pid;
+ GNUNET_PEER_change_rc (initiator_peer->ppd.pid, 1);
}
pth);
GNUNET_free (pth);
}
- GNUNET_PEER_change_rc (cp->pid, -1);
+ GNUNET_PEER_change_rc (cp->ppd.pid, -1);
+ if (GNUNET_SCHEDULER_NO_TASK != cp->mig_revive_task)
+ {
+ GNUNET_SCHEDULER_cancel (cp->mig_revive_task);
+ cp->mig_revive_task = GNUNET_SCHEDULER_NO_TASK;
+ }
GNUNET_free (cp);
}
GSF_connected_peer_get_identity_ (const struct GSF_ConnectedPeer *cp,
struct GNUNET_PeerIdentity *id)
{
- GNUNET_PEER_resolve (cp->pid,
+ GNUNET_PEER_resolve (cp->ppd.pid,
&id);
}
if (cp->trust == cp->disk_trust)
return GNUNET_OK; /* unchanged */
- GNUNET_PEER_resolve (cp->pid,
+ GNUNET_PEER_resolve (cp->ppd.pid,
&pid);
fn = get_trust_filename (&pid);
if (cp->trust == 0)
#include "platform.h"
#include "gnunet-service-fs_push.h"
-
-/* FIXME: below are only old code fragments to use... */
-
/**
* Block that is ready for migration to other peers. Actual data is at the end of the block.
*/
struct GNUNET_TIME_Absolute expiration;
/**
- * Peers we would consider forwarding this
+ * Peers we already forwarded this
* block to. Zero for empty entries.
*/
GNUNET_PEER_Id target_list[MIGRATION_LIST_SIZE];
};
+/**
+ * Information about a peer waiting for
+ * migratable data.
+ */
+struct MigrationReadyPeer
+{
+ /**
+ * This is a doubly-linked list.
+ */
+ struct MigrationReadyPeer *next;
+
+ /**
+ * This is a doubly-linked list.
+ */
+ struct MigrationReadyPeer *prev;
+
+ /**
+ * Handle to peer.
+ */
+ struct GSF_ConnectedPeer *peer;
+
+ /**
+ * Handle for current transmission request,
+ * or NULL for none.
+ */
+ struct GSF_PeerTransmitHandle *th;
+
+ /**
+ * Message we are trying to push right now (or NULL)
+ */
+ struct PutMessage *msg;
+};
+
+
/**
* Head of linked list of blocks that can be migrated.
*/
*/
static struct MigrationReadyBlock *mig_tail;
+/**
+ * Head of linked list of peers.
+ */
+static struct MigrationReadyPeer *peer_head;
+
+/**
+ * Tail of linked list of peers.
+ */
+static struct MigrationReadyPeer *peer_tail;
+
/**
* Request to datastore for migration (or NULL).
*/
static struct GNUNET_TIME_Relative min_migration_delay;
/**
- * Are we allowed to push out content from this peer.
+ * Size of the doubly-linked list of migration blocks.
*/
-static int active_from_migration;
+static unsigned int mig_size;
/**
- * Size of the doubly-linked list of migration blocks.
+ * Is this module enabled?
*/
-static unsigned int mig_size;
+static int enabled;
/**
/**
- * Compare the distance of two peers to a key.
+ * Find content for migration to this peer.
+ */
+static void
+find_content (struct MigrationReadyPeer *mrp);
+
+
+/**
+ * Transmit the message currently scheduled for
+ * transmission.
*
- * @param key key
- * @param p1 first peer
- * @param p2 second peer
- * @return GNUNET_YES if P1 is closer to key than P2
+ * @param cls the 'struct MigrationReadyPeer'
+ * @param buf_size number of bytes available in buf
+ * @param buf where to copy the message, NULL on error (peer disconnect)
+ * @return number of bytes copied to 'buf', can be 0 (without indicating an error)
*/
-static int
-is_closer (const GNUNET_HashCode *key,
- const struct GNUNET_PeerIdentity *p1,
- const struct GNUNET_PeerIdentity *p2)
+static size_t
+transmit_message (void *cls,
+ size_t buf_size,
+ void *buf)
{
- return GNUNET_CRYPTO_hash_xorcmp (&p1->hashPubKey,
- &p2->hashPubKey,
- key);
+ struct MigrationReadyPeer *peer = cls;
+ struct PutMessage *msg;
+ uint16_t msize;
+
+ peer->th = NULL;
+ msg = peer->msg;
+ peer->msg = NULL;
+ if (buf == NULL)
+ {
+ GNUNET_free (msg);
+ return 0;
+ }
+ msize = ntohs (msg->header.size);
+ GNUNET_assert (msize <= buf_size);
+ memcpy (buf, msg, msize);
+ GNUNET_free (msg);
+ find_content (peer);
+ return msize;
}
/**
- * Consider migrating content to a given peer.
+ * Send the given block to the given peer.
*
- * @param cls 'struct MigrationReadyBlock*' to select
- * targets for (or NULL for none)
- * @param key ID of the peer
- * @param value 'struct ConnectedPeer' of the peer
- * @return GNUNET_YES (always continue iteration)
+ * @param peer target peer
+ * @param block the block
+ * @return GNUNET_YES if the block was deleted (!)
*/
static int
-consider_migration (void *cls,
- const GNUNET_HashCode *key,
- void *value)
+transmit_content (struct MigrationReadyPeer *peer,
+ struct MigrationReadyBlock *block)
{
- struct MigrationReadyBlock *mb = cls;
- struct ConnectedPeer *cp = value;
- struct MigrationReadyBlock *pos;
- struct GNUNET_PeerIdentity cppid;
- struct GNUNET_PeerIdentity otherpid;
- struct GNUNET_PeerIdentity worstpid;
size_t msize;
- unsigned int i;
- unsigned int repl;
+ struct PutMessage *msg;
+ unsigned int i;
+ struct GSF_PeerPerformanceData *ppd;
+ int ret;
+
+ ppd = GSF_get_peer_performance_data (peer->peer);
+ GNUNET_assert (NULL == peer->th);
+ msize = sizeof (struct PutMessage) + block->size;
+ msg = GNUNET_malloc (msize);
+ msg->header.type = htons (42);
+ msg->header.size = htons (msize);
- /* consider 'cp' as a migration target for mb */
- if (GNUNET_TIME_absolute_get_remaining (cp->migration_blocked).rel_value > 0)
- return GNUNET_YES; /* peer has requested no migration! */
- if (mb != NULL)
+ memcpy (&msg[1],
+ &block[1],
+ block->size);
+ peer->msg = msg;
+ for (i=0;i<MIGRATION_LIST_SIZE;i++)
{
- GNUNET_PEER_resolve (cp->pid,
- &cppid);
- repl = MIGRATION_LIST_SIZE;
- for (i=0;i<MIGRATION_LIST_SIZE;i++)
+ if (block->target_list[i] == 0)
{
- if (mb->target_list[i] == 0)
- {
- mb->target_list[i] = cp->pid;
- GNUNET_PEER_change_rc (mb->target_list[i], 1);
- repl = MIGRATION_LIST_SIZE;
- break;
- }
- GNUNET_PEER_resolve (mb->target_list[i],
- &otherpid);
- if ( (repl == MIGRATION_LIST_SIZE) &&
- is_closer (&mb->query,
- &cppid,
- &otherpid))
- {
- repl = i;
- worstpid = otherpid;
- }
- else if ( (repl != MIGRATION_LIST_SIZE) &&
- (is_closer (&mb->query,
- &worstpid,
- &otherpid) ) )
- {
- repl = i;
- worstpid = otherpid;
- }
- }
- if (repl != MIGRATION_LIST_SIZE)
- {
- GNUNET_PEER_change_rc (mb->target_list[repl], -1);
- mb->target_list[repl] = cp->pid;
- GNUNET_PEER_change_rc (mb->target_list[repl], 1);
+ block->target_list[i] = ppd->pid;
+ GNUNET_PEER_change_rc (block->target_list[i], 1);
+ break;
}
}
+ if (MIGRATION_LIST_SIZE == i)
+ {
+ delete_migration_block (block);
+ ret = GNUNET_YES;
+ }
+ else
+ {
+ ret = GNUNET_NO;
+ }
+ peer->th = GSF_peer_transmit_ (peer->peer,
+ GNUNET_NO,
+ 0 /* priority */,
+ GNUNET_TIME_UNIT_FOREVER_REL,
+ msize,
+ &transmit_message,
+ peer);
+ return ret;
+}
- /* consider scheduling transmission to cp for content migration */
- if (cp->cth != NULL)
- return GNUNET_YES;
- msize = 0;
- pos = mig_head;
- while (pos != NULL)
+
+/**
+ * Count the number of peers this block has
+ * already been forwarded to.
+ *
+ * @param block the block
+ * @return number of times block was forwarded
+ */
+static unsigned int
+count_targets (struct MigrationReadyBlock *block)
+{
+ unsigned int i;
+
+ for (i=0;i<MIGRATION_LIST_SIZE;i++)
+ if (block->target_list[i] == 0)
+ return i;
+ return i;
+}
+
+
+/**
+ * Check if sending this block to this peer would
+ * be a good idea.
+ *
+ * @param peer target peer
+ * @param block the block
+ * @return score (>= 0: feasible, negative: infeasible)
+ */
+static long
+score_content (struct MigrationReadyPeer *peer,
+ struct MigrationReadyBlock *block)
+{
+ unsigned int i;
+ struct GSF_PeerPerformanceData *ppd;
+ struct GNUNET_PeerIdentity id;
+ uint32_t dist;
+
+ ppd = GSF_get_peer_performance_data (peer->peer);
+ for (i=0;i<MIGRATION_LIST_SIZE;i++)
+ if (mb->target_list[i] == ppd->pid)
+ return -1;
+ GSF_connected_peer_get_identity (peer->peer,
+ &id);
+ dist = GNUNET_CRYPTO_hash_distance_u32 (&block->query,
+ &id.hashPubKey);
+ /* closer distance, higher score: */
+ return UINT32_MAX - dist;
+}
+
+
+/**
+ * If the migration task is not currently running, consider
+ * (re)scheduling it with the appropriate delay.
+ */
+static void
+consider_gathering (void);
+
+
+/**
+ * Find content for migration to this peer.
+ *
+ * @param mig peer to find content for
+ */
+static void
+find_content (struct MigrationReadyPeer *mrp)
+{
+ struct MigrationReadyBlock *pos;
+ long score;
+ long best_score;
+ struct MigrationReadyBlock *best;
+
+ GNUNET_assert (NULL == mrp->th);
+ best = NULL;
+ best_score = -1;
+ pos = mig_qe;
+ while (NULL != pos)
{
- for (i=0;i<MIGRATION_LIST_SIZE;i++)
+ score = score_content (mrp, pos);
+ if (score > best_score)
{
- if (cp->pid == pos->target_list[i])
- {
- if (msize == 0)
- msize = pos->size;
- else
- msize = GNUNET_MIN (msize,
- pos->size);
- break;
- }
+ best_score = score;
+ best = mrp;
}
pos = pos->next;
}
- if (msize == 0)
- return GNUNET_YES; /* no content available */
-#if DEBUG_FS
- GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
- "Trying to migrate at least %u bytes to peer `%s'\n",
- msize,
- GNUNET_h2s (key));
-#endif
- if (cp->delayed_transmission_request_task != GNUNET_SCHEDULER_NO_TASK)
+ if ( (NULL == best) &&
+ (mig_size >= MAX_MIGRATION_QUEUE) )
{
- GNUNET_SCHEDULER_cancel (cp->delayed_transmission_request_task);
- cp->delayed_transmission_request_task = GNUNET_SCHEDULER_NO_TASK;
+ /* failed to find migration target AND
+ queue is full, purge most-forwarded
+ block from queue to make room for more */
+ score = 0;
+ pos = mig_qe;
+ while (NULL != pos)
+ {
+ score = count_targets (pos);
+ if (score >= best_score)
+ {
+ best_score = score;
+ best = mrp;
+ }
+ pos = pos->next;
+ }
+ GNUNET_assert (NULL != best);
+ delete_migration_block (best);
+ consider_gathering ();
+ return;
}
- cp->cth
- = GNUNET_CORE_notify_transmit_ready (core,
- 0, GNUNET_TIME_UNIT_FOREVER_REL,
- (const struct GNUNET_PeerIdentity*) key,
- msize + sizeof (struct PutMessage),
- &transmit_to_peer,
- cp);
- return GNUNET_YES;
+ transmit_content (peer, best);
}
const struct GNUNET_SCHEDULER_TaskContext *tc);
-
-
/**
* If the migration task is not currently running, consider
* (re)scheduling it with the appropriate delay.
*/
static void
-consider_migration_gathering ()
+consider_gathering ()
{
struct GNUNET_TIME_Relative delay;
- if (dsh == NULL)
+ if (GSF_dsh == NULL)
return;
if (mig_qe != NULL)
return;
if (mig_task != GNUNET_SCHEDULER_NO_TASK)
return;
+ if (mig_size >= MAX_MIGRATION_QUEUE)
+ return;
delay = GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS,
mig_size);
delay = GNUNET_TIME_relative_divide (delay,
}
-
-
/**
* Process content offered for migration.
*
expiration, uint64_t uid)
{
struct MigrationReadyBlock *mb;
+ struct MigrationReadyPeer *pos;
if (key == NULL)
{
mig_qe = NULL;
- if (mig_size < MAX_MIGRATION_QUEUE)
- consider_migration_gathering ();
+ consider_gathering ();
return;
}
if (GNUNET_TIME_absolute_get_remaining (expiration).rel_value <
MIN_MIGRATION_CONTENT_LIFETIME.rel_value)
{
/* content will expire soon, don't bother */
- GNUNET_DATASTORE_get_next (dsh, GNUNET_YES);
+ GNUNET_DATASTORE_get_next (GSF_dsh, GNUNET_YES);
return;
}
if (type == GNUNET_BLOCK_TYPE_FS_ONDEMAND)
&process_migration_content,
NULL))
{
- GNUNET_DATASTORE_get_next (dsh, GNUNET_YES);
+ GNUNET_DATASTORE_get_next (GSF_dsh, GNUNET_YES);
}
return;
}
mig_tail,
mb);
mig_size++;
- GNUNET_CONTAINER_multihashmap_iterate (connected_peers,
- &consider_migration,
- mb);
- GNUNET_DATASTORE_get_next (dsh, GNUNET_YES);
+ pos = peer_head;
+ while (pos != NULL)
+ {
+ if (NULL == pos->th)
+ {
+ if (GNUNET_YES == transmit_content (pos, mb))
+ break; /* 'mb' was freed! */
+ }
+ pos = pos->next;
+ }
+ GNUNET_DATASTORE_get_next (GSF_dsh, GNUNET_YES);
}
-
/**
* Task that is run periodically to obtain blocks for content
* migration
const struct GNUNET_SCHEDULER_TaskContext *tc)
{
mig_task = GNUNET_SCHEDULER_NO_TASK;
- if (dsh != NULL)
+ if (GSF_dsh != NULL)
{
- mig_qe = GNUNET_DATASTORE_get_random (dsh, 0, UINT_MAX,
+ mig_qe = GNUNET_DATASTORE_get_random (GSF_dsh,
+ 0, UINT_MAX,
GNUNET_TIME_UNIT_FOREVER_REL,
&process_migration_content, NULL);
GNUNET_assert (mig_qe != NULL);
}
+/**
+ * A peer connected to us. Start pushing content
+ * to this peer.
+ *
+ * @param peer handle for the peer that connected
+ */
+void
+GSF_push_start_ (struct GSF_ConnectedPeer *peer)
+{
+ struct MigrationReadyPeer *mrp;
-size_t
-API_ (void *cls,
- size_t size, void *buf)
+ if (GNUNET_YES != enabled)
+ return;
+ mrp = GNUNET_malloc (sizeof (struct MigrationReadyPeer));
+ mrp->peer = peer;
+ find_content (mrp);
+ GNUNET_CONTAINER_DLL_insert (peer_head,
+ peer_tail,
+ mrp);
+}
+
+
+/**
+ * A peer disconnected from us. Stop pushing content
+ * to this peer.
+ *
+ * @param peer handle for the peer that disconnected
+ */
+void
+GSF_push_stop_ (struct GSF_ConnectedPeer *peer)
{
- next = mig_head;
- while (NULL != (mb = next))
+ struct MigrationReadyPeer *pos;
+
+ pos = peer_head;
+ while (pos != NULL)
+ {
+ if (pos->peer == peer)
{
- next = mb->next;
- for (i=0;i<MIGRATION_LIST_SIZE;i++)
- {
- if ( (cp->pid == mb->target_list[i]) &&
- (mb->size + sizeof (migm) <= size) )
- {
- GNUNET_PEER_change_rc (mb->target_list[i], -1);
- mb->target_list[i] = 0;
- mb->used_targets++;
- memset (&migm, 0, sizeof (migm));
- migm.header.size = htons (sizeof (migm) + mb->size);
- migm.header.type = htons (GNUNET_MESSAGE_TYPE_FS_PUT);
- migm.type = htonl (mb->type);
- migm.expiration = GNUNET_TIME_absolute_hton (mb->expiration);
- memcpy (&cbuf[msize], &migm, sizeof (migm));
- msize += sizeof (migm);
- size -= sizeof (migm);
- memcpy (&cbuf[msize], &mb[1], mb->size);
- msize += mb->size;
- size -= mb->size;
-#if DEBUG_FS
- GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
- "Pushing migration block `%s' (%u bytes) to `%s'\n",
- GNUNET_h2s (&mb->query),
- (unsigned int) mb->size,
- GNUNET_i2s (&pid));
-#endif
- break;
- }
- else
- {
-#if DEBUG_FS
- GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
- "Migration block `%s' (%u bytes) is not on migration list for peer `%s'\n",
- GNUNET_h2s (&mb->query),
- (unsigned int) mb->size,
- GNUNET_i2s (&pid));
-#endif
- }
- }
- if ( (mb->used_targets >= MIGRATION_TARGET_COUNT) ||
- (mb->used_targets >= GNUNET_CONTAINER_multihashmap_size (connected_peers)) )
- {
- delete_migration_block (mb);
- consider_migration_gathering ();
- }
+ GNUNET_CONTAINER_DLL_remove (peer_head,
+ peer_tail,
+ pos);
+ if (NULL != pos->th)
+ GSF_peer_transmit_cancel_ (pos->th);
+ GNUNET_free (pos);
+ return;
}
- consider_migration (NULL,
- &pid.hashPubKey,
- cp);
+ pos = pos->next;
+ }
+}
+
+/**
+ * Setup the module.
+ *
+ * @param cfg configuration to use
+ */
+void
+GSF_push_init_ (struct GNUNET_CONFIGURATION_Handle *cfg)
+{
+ int enabled;
+
+ enabled = GNUNET_CONFIGURATION_get_value_yesno (cfg,
+ "FS",
+ "CONTENT_PUSHING");
+ if (GNUNET_YES != enabled)
+ return;
+
+ if (GNUNET_OK !=
+ GNUNET_CONFIGURATION_get_value_time (cfg,
+ "fs",
+ "MIN_MIGRATION_DELAY",
+ &min_migration_delay))
+ {
+ GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+ _("Invalid value specified for option `%s' in section `%s', content pushing disabled\n"),
+ "MIN_MIGRATION_DELAY",
+ "fs");
+ return;
+ }
+ consider_gathering ();
}
+/**
+ * Shutdown the module.
+ */
+void
+GSF_push_done_ ()
+{
+ if (GNUNET_SCHEDULER_NO_TASK != mig_task)
+ {
+ GNUNET_SCHEDULER_cancel (mig_task);
+ mig_task = GNUNET_SCHEDULER_NO_TASK;
+ }
+ if (NULL != mig_qe)
+ {
+ GNUNET_DATASTORE_cancel (mig_qe);
+ mig_qe = NULL;
+ }
+ while (NULL != mig_head)
+ delete_migration_block (mig_head);
+ GNUNET_assert (0 == mig_size);
+}
+/* end of gnunet-service-fs_push.c */