ipcpd: Use capacity queue estimation for mb-ecn

The mb-ecn algorithm was using rbuff queue depths in packets to mark,
but sockets in the poa component report capacity in bytes. The tx
rings are now adaptive to block on queuing delay instead of when full
to prevent buffer bloat, controllable via fccntl (FLOWSTXQDLY and
FLOWGTXQDLY).

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 63 insertions, 0 deletions

diff --git a/src/lib/cap.h b/src/lib/cap.h
new file mode 100644
index 00000000..3d94d9a3
--- /dev/null
+++ b/src/lib/cap.h
@@ -0,0 +1,63 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2026
+ *
+ * Link capacity estimation
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef OUROBOROS_LIB_CAP_H
+#define OUROBOROS_LIB_CAP_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define CAP_ALIGN 64
+
+struct cap_est {
+        uint64_t c_pkt;  /* total packets enqueued (relaxed)  */
+        uint64_t c_byt;  /* total bytes enqueued (relaxed)    */
+        uint64_t c_idl;  /* times ring seen empty (relaxed)   */
+
+        uint64_t t_gate; /* last window close (ns)            */
+        uint64_t t_last; /* last update, to spot a gap (ns)   */
+        uint8_t  busy;   /* close in progress (try-lock)      */
+
+        uint64_t t0;     /* window start (ns), 0 = no window  */
+        uint64_t q0;     /* ring occupancy at window start    */
+        uint64_t pkt0;   /* c_pkt snapshot at window start    */
+        uint64_t byt0;   /* c_byt snapshot at window start    */
+        uint64_t idl0;   /* c_idl snapshot at window start    */
+        uint64_t rate;   /* filtered drain rate (bytes/s)     */
+
+        uint64_t est;    /* published estimate (bytes/s)      */
+} __attribute__((aligned(CAP_ALIGN)));
+
+void     cap_clear(struct cap_est * e);
+
+void     cap_update(struct cap_est * e,
+                    size_t           qlen,
+                    size_t           len);
+
+void     cap_update_at(struct cap_est * e,
+                       size_t           qlen,
+                       size_t           len,
+                       uint64_t         now);
+
+uint64_t cap_rate(const struct cap_est * e);
+
+#endif /* OUROBOROS_LIB_CAP_H */