1 files changed, 160 insertions, 0 deletions
diff --git a/lib/ngtcp2_pmtud.c b/lib/ngtcp2_pmtud.c
new file mode 100644
index 0000000..771ef5e
--- /dev/null
+++ b/lib/ngtcp2_pmtud.c
@@ -0,0 +1,160 @@
+/*
+ * ngtcp2
+ *
+ * Copyright (c) 2022 ngtcp2 contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "ngtcp2_pmtud.h"
+
+#include <assert.h>
+
+#include "ngtcp2_mem.h"
+#include "ngtcp2_macro.h"
+
+/* NGTCP2_PMTUD_PROBE_NUM_MAX is the maximum number of packets sent
+   for each probe. */
+#define NGTCP2_PMTUD_PROBE_NUM_MAX 3
+
+static size_t mtu_probes[] = {
+    1454 - 48, /* The well known MTU used by a domestic optic fiber
+                  service in Japan. */
+    1390 - 48, /* Typical Tunneled MTU */
+    1280 - 48, /* IPv6 minimum MTU */
+    1492 - 48, /* PPPoE */
+};
+
+#define NGTCP2_MTU_PROBESLEN ngtcp2_arraylen(mtu_probes)
+
+int ngtcp2_pmtud_new(ngtcp2_pmtud **ppmtud, size_t max_udp_payload_size,
+                     size_t hard_max_udp_payload_size, int64_t tx_pkt_num,
+                     const ngtcp2_mem *mem) {
+  ngtcp2_pmtud *pmtud = ngtcp2_mem_malloc(mem, sizeof(ngtcp2_pmtud));
+
+  if (pmtud == NULL) {
+    return NGTCP2_ERR_NOMEM;
+  }
+
+  pmtud->mem = mem;
+  pmtud->mtu_idx = 0;
+  pmtud->num_pkts_sent = 0;
+  pmtud->expiry = UINT64_MAX;
+  pmtud->tx_pkt_num = tx_pkt_num;
+  pmtud->max_udp_payload_size = max_udp_payload_size;
+  pmtud->hard_max_udp_payload_size = hard_max_udp_payload_size;
+  pmtud->min_fail_udp_payload_size = SIZE_MAX;
+
+  for (; pmtud->mtu_idx < NGTCP2_MTU_PROBESLEN; ++pmtud->mtu_idx) {
+    if (mtu_probes[pmtud->mtu_idx] > pmtud->hard_max_udp_payload_size) {
+      continue;
+    }
+    if (mtu_probes[pmtud->mtu_idx] > pmtud->max_udp_payload_size) {
+      break;
+    }
+  }
+
+  *ppmtud = pmtud;
+
+  return 0;
+}
+
+void ngtcp2_pmtud_del(ngtcp2_pmtud *pmtud) {
+  if (!pmtud) {
+    return;
+  }
+
+  ngtcp2_mem_free(pmtud->mem, pmtud);
+}
+
+size_t ngtcp2_pmtud_probelen(ngtcp2_pmtud *pmtud) {
+  assert(pmtud->mtu_idx < NGTCP2_MTU_PROBESLEN);
+
+  return mtu_probes[pmtud->mtu_idx];
+}
+
+void ngtcp2_pmtud_probe_sent(ngtcp2_pmtud *pmtud, ngtcp2_duration pto,
+                             ngtcp2_tstamp ts) {
+  ngtcp2_tstamp timeout;
+
+  if (++pmtud->num_pkts_sent < NGTCP2_PMTUD_PROBE_NUM_MAX) {
+    timeout = pto;
+  } else {
+    timeout = 3 * pto;
+  }
+
+  pmtud->expiry = ts + timeout;
+}
+
+int ngtcp2_pmtud_require_probe(ngtcp2_pmtud *pmtud) {
+  return pmtud->expiry == UINT64_MAX;
+}
+
+static void pmtud_next_probe(ngtcp2_pmtud *pmtud) {
+  assert(pmtud->mtu_idx < NGTCP2_MTU_PROBESLEN);
+
+  ++pmtud->mtu_idx;
+  pmtud->num_pkts_sent = 0;
+  pmtud->expiry = UINT64_MAX;
+
+  for (; pmtud->mtu_idx < NGTCP2_MTU_PROBESLEN; ++pmtud->mtu_idx) {
+    if (mtu_probes[pmtud->mtu_idx] <= pmtud->max_udp_payload_size ||
+        mtu_probes[pmtud->mtu_idx] > pmtud->hard_max_udp_payload_size) {
+      continue;
+    }
+
+    if (mtu_probes[pmtud->mtu_idx] < pmtud->min_fail_udp_payload_size) {
+      break;
+    }
+  }
+}
+
+void ngtcp2_pmtud_probe_success(ngtcp2_pmtud *pmtud, size_t payloadlen) {
+  pmtud->max_udp_payload_size =
+      ngtcp2_max(pmtud->max_udp_payload_size, payloadlen);
+
+  assert(pmtud->mtu_idx < NGTCP2_MTU_PROBESLEN);
+
+  if (mtu_probes[pmtud->mtu_idx] > pmtud->max_udp_payload_size) {
+    return;
+  }
+
+  pmtud_next_probe(pmtud);
+}
+
+void ngtcp2_pmtud_handle_expiry(ngtcp2_pmtud *pmtud, ngtcp2_tstamp ts) {
+  if (ts < pmtud->expiry) {
+    return;
+  }
+
+  pmtud->expiry = UINT64_MAX;
+
+  if (pmtud->num_pkts_sent < NGTCP2_PMTUD_PROBE_NUM_MAX) {
+    return;
+  }
+
+  pmtud->min_fail_udp_payload_size =
+      ngtcp2_min(pmtud->min_fail_udp_payload_size, mtu_probes[pmtud->mtu_idx]);
+
+  pmtud_next_probe(pmtud);
+}
+
+int ngtcp2_pmtud_finished(ngtcp2_pmtud *pmtud) {
+  return pmtud->mtu_idx >= NGTCP2_MTU_PROBESLEN;
+}