From 8e6b6d04b11d3a2a4fd8413555414c5f8e500915 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 28 Jul 2021 17:16:06 +0200
Subject: introduce timer_new_opaque callback

Add a new callback that supports CFI better by avoiding having function pointers
in the external libslirp API.  Instead, the new API passes an opaque integer
and requests the application to call a new libslirp function when the timer
expires.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 src/libslirp.h   | 16 +++++++++++++++-
 src/libslirp.map |  4 ++++
 src/slirp.c      | 17 +++++++++++++++++
 src/slirp.h      |  2 ++
 4 files changed, 38 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/libslirp.h b/src/libslirp.h
index 546f2f9..8eb47a0 100644
--- a/src/libslirp.h
+++ b/src/libslirp.h
@@ -63,7 +63,8 @@ typedef struct SlirpCb {
     void (*guest_error)(const char *msg, void *opaque);
     /* Return the virtual clock value in nanoseconds */
     int64_t (*clock_get_ns)(void *opaque);
-    /* Create a new timer with the given callback and opaque data */
+    /* Create a new timer with the given callback and opaque data. Not
+     * needed if timer_new_opaque is provided. */
     void *(*timer_new)(SlirpTimerCb cb, void *cb_opaque, void *opaque);
     /* Remove and free a timer */
     void (*timer_free)(void *timer, void *opaque);
@@ -76,6 +77,14 @@ typedef struct SlirpCb {
     /* Kick the io-thread, to signal that new events may be processed because some TCP buffer
      * can now receive more data, i.e. slirp_socket_can_recv will return 1. */
     void (*notify)(void *opaque);
+
+    /*
+     * Fields introduced in SlirpConfig version 4 begin
+     */
+
+    /* Create a new timer.  When the timer fires, the application passes
+     * the SlirpTimerId and cb_opaque to slirp_handle_timer.  */
+    void *(*timer_new_opaque)(SlirpTimerId id, void *cb_opaque, void *opaque);
 } SlirpCb;
 
 #define SLIRP_CONFIG_VERSION_MIN 1
@@ -171,6 +180,11 @@ void slirp_pollfds_poll(Slirp *slirp, int select_error,
  * guest network, to be interpreted by slirp. */
 void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len);
 
+/* This is called by the application when a timer expires, if it provides
+ * the timer_new_opaque callback.  It is not needed if the application only
+ * uses timer_new. */
+void slirp_handle_timer(Slirp *slirp, SlirpTimerId id, void *cb_opaque);
+
 /* These set up / remove port forwarding between a host port in the real world
  * and the guest network. */
 int slirp_add_hostfwd(Slirp *slirp, int is_udp, struct in_addr host_addr,
diff --git a/src/libslirp.map b/src/libslirp.map
index 792b0a9..3921f8a 100644
--- a/src/libslirp.map
+++ b/src/libslirp.map
@@ -34,3 +34,7 @@ SLIRP_4.5 {
     slirp_remove_hostxfwd;
     slirp_neighbor_info;
 } SLIRP_4.2;
+
+SLIRP_4.7 {
+    slirp_handle_timer;
+} SLIRP_4.5;
diff --git a/src/slirp.c b/src/slirp.c
index a2876f2..c92a9a9 100644
--- a/src/slirp.c
+++ b/src/slirp.c
@@ -535,10 +535,26 @@ static void ra_timer_handler_cb(void *opaque)
     return ra_timer_handler(slirp, NULL);
 }
 
+void slirp_handle_timer(Slirp *slirp, SlirpTimerId id, void *cb_opaque)
+{
+    g_return_if_fail(id >= 0 && id < SLIRP_TIMER_NUM);
+
+    switch (id) {
+    case SLIRP_TIMER_RA:
+        return ra_timer_handler(slirp, cb_opaque);
+    default:
+        abort();
+    }
+}
+
 void *slirp_timer_new(Slirp *slirp, SlirpTimerId id, void *cb_opaque)
 {
     g_return_val_if_fail(id >= 0 && id < SLIRP_TIMER_NUM, NULL);
 
+    if (slirp->cfg_version >= 4 && slirp->cb->timer_new_opaque) {
+        return slirp->cb->timer_new_opaque(id, cb_opaque, slirp->opaque);
+    }
+
     switch (id) {
     case SLIRP_TIMER_RA:
         g_return_val_if_fail(cb_opaque == NULL, NULL);
@@ -568,6 +584,7 @@ Slirp *slirp_new(const SlirpConfig *cfg, const SlirpCb *callbacks, void *opaque)
 
     slirp_init_once();
 
+    slirp->cfg_version = cfg->version;
     slirp->opaque = opaque;
     slirp->cb = callbacks;
     slirp->grand = g_rand_new();
diff --git a/src/slirp.h b/src/slirp.h
index bfe7b83..50e33a5 100644
--- a/src/slirp.h
+++ b/src/slirp.h
@@ -120,6 +120,8 @@ bool ndp_table_search(Slirp *slirp, struct in6_addr ip_addr,
                       uint8_t out_ethaddr[ETH_ALEN]);
 
 struct Slirp {
+    int cfg_version;
+
     unsigned time_fasttimo;
     unsigned last_slowtimo;
     bool do_slowtimo;
-- 
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