Configure TCP ACK ceiling per interface

docs/aminet-survey/own-tools.tsv

@@ -5,7 +5,7 @@ offset	lvo	aminet_callers	our_tool_mentions
 -48	accept	245	40
 -54	connect	600	21
 -60	sendto	217	1
--66	send	758	83
+-66	send	758	84
 -72	recvfrom	198	2
 -78	recv	696	17
 -84	shutdown	198	8

docs/user/AmiNetXDuo.guide

@@ -467,6 +467,17 @@
              ring overflowed 42 times in ten seconds and the card
              received 2.8 Mbit/s.
 
+  @{b}TCPACKMAX@{ub}
+             Maximum received TCP bytes between requested ACKs on
+             connections using this interface, 1 to 65535. Smaller
+             values send more ACKs and may improve Wi-Fi receive speed
+             at a cost in transmit work. Leave it out for the device
+             default: 11680 for anxwifipi.device and wifipi.device,
+             50176 for other devices. An explicit value wins on this
+             interface only; editing the file takes effect when the
+             interface is next attached. This is a TCP stack setting,
+             not a SANA-II driver command.
+
   Interface files written for Roadshow usually carry other keywords:
   COPYMODE, ALIAS, METRIC, LEASE, DHCPUNICAST, LINKSTATUSCOMMAND,
   MULTICAST, POINTTOPOINT, DESTINATION and BROADCASTADDRESS among

include/aminetxduo/config.h

@@ -54,6 +54,7 @@ extern "C" {
 #define AMINETXDUO_TX_SLOTS         32
 #endif
 #define AMI_CFG_WRITEREQUESTS_MAX   AMINETXDUO_TX_SLOTS
+#define AMI_CFG_TCP_ACK_MAX         65535UL
 #define AMI_CFG_PATH_LEN            128
 
 /* The default domain gets its own cap: SetDefaultDomainName()'s autodoc says
@@ -199,6 +200,9 @@ typedef struct AmiIfConfig {
      * hardware is known gets a default by name.  A number here wins.
      */
     ULONG       rx_buffer;
+    /* TCPACKMAX: maximum unacknowledged receive bytes before an ACK is
+       requested on connections using this interface.  0 = device default. */
+    ULONG       tcp_ack_max;
     BYTE        priority;                    /* PRIORITY=, -128..127, 0 unset: the
                                                 highest wins a route two
                                                 interfaces could carry        */

include/aminetxduo/config_advice.h

@@ -64,5 +64,6 @@
 #define AMI_CFG_ADVICE_RXBUFFER_IS_THE                   49
 #define AMI_CFG_ADVICE_PRIORITY_IS_A_SMALL                50
 #define AMI_CFG_ADVICE_FILTER_IS_LOCAL_IPANDARP          51
+#define AMI_CFG_ADVICE_TCPACKMAX_IS_ACK_BYTES            52
 
 #endif /* AMINETXDUO_CONFIG_ADVICE_H */

include/aminetxduo/sana2.h

@@ -72,6 +72,11 @@ UWORD       ami_sana2_retained_count(VOID);
    refuses such a pair with AMI_NET_ERR_RETAINED before OpenDevice(). */
 ULONG       ami_sana2_retained_holds(const char *device, ULONG unit);
 
+/* TCP ACK ceiling when TCPACKMAX is absent: WiFiPi needs the measured
+   one-GRO-run cadence, other devices use the NetX port default.  Zero means
+   use that port default.  Names are compared by basename, ignoring case. */
+ULONG       ami_sana2_default_tcp_ack_max(const char *device);
+
 /*
  * Collect whatever the devices have given back since, without waiting, and
  * CloseDevice() and free every interface nothing holds any more.  Under

install/Install-AmiNetXDuo

@@ -2238,6 +2238,8 @@
     (append ";               keyword is absent.  The responder costs\n")
     (append ";               real time on a slow machine, even when\n")
     (append ";               nothing asks it anything.\n")
+    (append "; TCPACKMAX= caps received TCP bytes between requested ACKs.\n")
+    (append ";             Leave it out for this device's default.\n")
     (append ";\n")
     (append "; An IPv6 build also understands CONFIGURE6 (OFF, LINKLOCAL,\n")
     (append "; AUTO, DHCP or STATIC), ADDRESS6 and GATEWAY6.  A build\n")

src/config/config_advice.c

@@ -126,6 +126,9 @@ static const char *const ami_cfg_advice_text[] =
     "FILTER is LOCAL, IPANDARP or EVERYTHING.  The first two are wha"
     "t happens anyway.  EVERYTHING opens the driver promiscuous, for"
     " a card whose multicast filter lets nothing through.",
+    "TCPACKMAX is the maximum number of received TCP bytes to wait "
+    "before requesting an ACK, 1 to 65535. Leave it out for the "
+    "device default; smaller values send more ACKs.",
 };
 
 const char *ami_cfg_advice(UWORD code)

src/config/config_parse.c

@@ -43,6 +43,7 @@ typedef enum
     IF_KEY_ARPREQUESTS,
     IF_KEY_WRITEREQUESTS,
     IF_KEY_RXBUFFER,
+    IF_KEY_TCPACKMAX,
     IF_KEY_PRIORITY
 } IfKey;
 
@@ -76,6 +77,7 @@ ami_if_keywords[] =
     { "arprequests",        IF_KEY_ARPREQUESTS       },
     { "writerequests",      IF_KEY_WRITEREQUESTS     },
     { "rxbuffer",           IF_KEY_RXBUFFER          },
+    { "tcpackmax",          IF_KEY_TCPACKMAX         },
     { "priority",           IF_KEY_PRIORITY          },   /* Roadshow's, and PRI */
     { "pri",                IF_KEY_PRIORITY          },
 
@@ -763,6 +765,21 @@ LONG ami_cfg_parse_interface(const char *name, char *buf, AmiIfConfig *out)
                 }
                 break;
 
+            case IF_KEY_TCPACKMAX:
+                if (ami_cfg_parse_ulong(value, &n) &&
+                    n != 0 && n <= AMI_CFG_TCP_ACK_MAX)
+                {
+                    out->tcp_ack_max = n;
+                }
+                else
+                {
+                    AMI_WARN("config: %s: bad TCPACKMAX '%s'", out->name, value);
+                    report_bad_value(lineno, AMI_CFG_PROBLEM_WARN,
+                                     "TCPACKMAX", value,
+                                     AMI_CFG_ADVICE_TCPACKMAX_IS_ACK_BYTES);
+                }
+                break;
+
             case IF_KEY_IPREQUESTS:
             case IF_KEY_ARPREQUESTS:
             case IF_KEY_WRITEREQUESTS:

src/config/test/test_config.c

@@ -1117,6 +1117,39 @@ static void test_request_counts_have_ceilings(void)
     CHECK(seen[1].line == 4);
     CHECK(seen[1].severity == AMI_CFG_PROBLEM_WARN);
 }
+static void test_interface_tcp_ack_max(void)
+{
+    AmiIfConfig iface;
+    char       *buf;
+
+    printf("interface: TCPACKMAX is optional and bounded per interface\n");
+
+    buf = dup_text("device = anxwifipi.device\nconfigure = dhcp\n"
+                   "tcpackmax = 11680\n");
+    CHECK(ami_cfg_parse_interface("wifipi", buf, &iface) == AMI_CFG_OK);
+    CHECK(iface.tcp_ack_max == 11680UL);
+    free(buf);
+
+    seen_count = 0;
+    ami_config_set_reporter(collect, NULL);
+    ami_cfg_problem_file("DEVS:NetInterfaces/wifipi");
+    buf = dup_text("device = anxwifipi.device\nconfigure = dhcp\n"
+                   "tcpackmax = 0\n");
+    CHECK(ami_cfg_parse_interface("wifipi", buf, &iface) == AMI_CFG_OK);
+    CHECK(iface.tcp_ack_max == 0);
+    CHECK(seen_count == 1 && seen[0].line == 3);
+    free(buf);
+
+    seen_count = 0;
+    buf = dup_text("device = anxwifipi.device\nconfigure = dhcp\n"
+                   "tcpackmax = 65536\n");
+    CHECK(ami_cfg_parse_interface("wifipi", buf, &iface) == AMI_CFG_OK);
+    CHECK(iface.tcp_ack_max == 0);
+    CHECK(seen_count == 1 && seen[0].line == 3);
+    free(buf);
+    ami_config_set_reporter(NULL, NULL);
+}
+
 static void test_interface_priority(void)
 {
     AmiIfConfig iface;
@@ -2934,6 +2967,7 @@ int main(int argc, char **argv)
     test_problem_reporter();
     test_inert_keywords_are_notes();
     test_request_counts_have_ceilings();
+    test_interface_tcp_ack_max();
     test_interface_priority();
     test_interface_ipv6_only();
 #ifdef AMINETXDUO_IPV6

src/netstack/netstack.c

@@ -532,10 +532,20 @@ static VOID ami_ns_park_unaddressed(AmiNetStack *ns, UWORD index)
  * keep attach order, which without this line is the whole rule -- a 3c589 in
  * slot 0 carried a subnet an anxgenet.device in slot 1 shares.
  */
-static VOID ami_ns_apply_priority(AmiNetStack *ns, UWORD index)
+static VOID ami_ns_apply_interface_policy(AmiNetStack *ns, UWORD index)
 {
     ns->ns_Ip.nx_ip_interface[index].nx_interface_priority =
         (INT)ns->ns_Config.interfaces[index].priority;
+
+    /* A TCP connection keeps its NX_INTERFACE for its lifetime.  Publish the
+       ACK policy before bringing this interface online; zero leaves NetX at
+       the port default (50176), while WiFiPi defaults to the measured 11680.
+       An explicit TCPACKMAX always wins for this interface alone. */
+    ns->ns_Ip.nx_ip_interface[index].nx_interface_tcp_ack_threshold_max =
+        (ns->ns_Config.interfaces[index].tcp_ack_max != 0)
+            ? ns->ns_Config.interfaces[index].tcp_ack_max
+            : ami_sana2_default_tcp_ack_max(
+                  ns->ns_Config.interfaces[index].device);
 }
 
 /*
@@ -809,7 +819,7 @@ static LONG ami_ns_create_ip(AmiNetStack *ns)
     for (i = 0; i < ns->ns_IfaceCount; i++)
     {
         ami_ns_park_unaddressed(ns, i);
-        ami_ns_apply_priority(ns, i);
+        ami_ns_apply_interface_policy(ns, i);
 
         if (ns->ns_Ip.nx_ip_interface[i].nx_interface_link_up == NX_FALSE)
             ami_event(NETEVENT_LINK_DOWN, i, 0UL);
@@ -3270,7 +3280,7 @@ static LONG ami_ns_interface_add_locked(const AmiIfConfig *cfg,
         ns->ns_IfaceCount = (UWORD)(slot + 1);
 
     ami_ns_park_unaddressed(ns, (UWORD)slot);
-    ami_ns_apply_priority(ns, (UWORD)slot);
+    ami_ns_apply_interface_policy(ns, (UWORD)slot);
     ns->ns_Ip.nx_ip_interface[slot].nx_interface_ip_conflict_notify_handler =
         ami_ns_ip_conflict;
 

src/sana2/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_library(aminetxduo_sana2 STATIC
     sana2_device.c
+    sana2_policy.c
     sana2_copy.c
     sana2_rx.c
     sana2_tx.c

src/sana2/sana2_policy.c

@@ -0,0 +1,38 @@
+/* Pure device-name defaults shared by the driver and host netstack tests. */
+#include "aminetxduo/sana2.h"
+
+static char lower_ascii(char c)
+{
+    if (c >= 'A' && c <= 'Z')
+        return (char)(c + ('a' - 'A'));
+    return c;
+}
+
+static int name_equal(const char *a, const char *b)
+{
+    while (*a != '\0' && *b != '\0')
+    {
+        if (lower_ascii(*a++) != lower_ascii(*b++))
+            return 0;
+    }
+    return *a == *b;
+}
+
+ULONG ami_sana2_default_tcp_ack_max(const char *device)
+{
+    const char *base = device;
+    const char *p;
+
+    if (device == NULL)
+        return 0;
+
+    for (p = device; *p != '\0'; p++)
+        if (*p == '/' || *p == ':')
+            base = p + 1;
+
+    if (name_equal(base, "anxwifipi.device") ||
+        name_equal(base, "wifipi.device"))
+        return 11680UL;
+
+    return 0;
+}

tests/netstack/CMakeLists.txt

@@ -963,6 +963,7 @@ if(NOT CMAKE_CROSSCOMPILING)
     # because that is the shipping default and its handful of entry points are
     # already answered.
     set(NETSTACK_HOST_TU
+        "${CMAKE_SOURCE_DIR}/src/sana2/sana2_policy.c"
         "${CMAKE_SOURCE_DIR}/src/netstack/netstack.c"
         "${CMAKE_SOURCE_DIR}/src/netstack/netstack_caller.c"
         "${CMAKE_SOURCE_DIR}/src/netstack/netstack_claim.c"

tests/netstack/host/test_config_routes_host.c

@@ -118,11 +118,58 @@ static void t_loopback_then_specific_route(void)
     h_down();
 }
 
+static void t_interface_tcp_ack_policy(void)
+{
+    static const struct {
+        const char *device;
+        ULONG requested;
+        ULONG expected;
+    } cases[] = {
+        { "RAM:anxwifipi.device", 0, 11680UL },
+        { "genet.device", 0, 0 },
+        { "genet.device", 8192UL, 8192UL },
+        { "RAM:anxwifipi.device", 4096UL, 4096UL }
+    };
+    AmiIfConfig cfg;
+    UWORD index;
+    unsigned int i;
+
+    printf("interface: TCP ACK policy follows the attached device and override\n");
+
+    for (i = 0; i < sizeof(cases) / sizeof(cases[0]); i++)
+    {
+        nsh_reset();
+        CHECK(netstack_startup_loopback() == AMI_NET_OK,
+              "the loopback stack starts for the ACK policy case");
+
+        memset(&cfg, 0, sizeof(cfg));
+        strcpy(cfg.name, "testif");
+        strcpy(cfg.device, cases[i].device);
+        cfg.iptype = AMI_IPTYPE_STATIC;
+        cfg.address = 0xC0A80132UL;
+        cfg.netmask = 0xFFFFFF00UL;
+        cfg.up = TRUE;
+        cfg.configured = TRUE;
+        cfg.tcp_ack_max = cases[i].requested;
+        index = 99;
+
+        CHECK(netstack_interface_start(&cfg, &index) == AMI_NET_OK && index == 0,
+              "the selected interface attaches in slot zero");
+        if (index == 0)
+            CHECK(netstack_get()->ns_Ip.nx_ip_interface[index]
+                      .nx_interface_tcp_ack_threshold_max == cases[i].expected,
+                  "the attached interface carries its own ACK ceiling");
+
+        h_down();
+    }
+}
+
 int main(void)
 {
     t_startup_installs();
     t_late_address_and_operator_delete();
     t_loopback_then_specific_route();
+    t_interface_tcp_ack_policy();
 
     printf("\n%lu checks, %lu failure(s)\n", h_checks, h_failures);
     return h_failures == 0 ? 0 : 1;

tests/sana2/CMakeLists.txt

@@ -249,6 +249,7 @@ add_test(NAME sana2_driver COMMAND test_sana2_driver)
 add_executable(test_sana2_device
     host/test_sana2_device_host.c
     "${CMAKE_SOURCE_DIR}/src/sana2/sana2_device.c"
+    "${CMAKE_SOURCE_DIR}/src/sana2/sana2_policy.c"
     "${CMAKE_SOURCE_DIR}/src/sana2/sana2_txmeta.c")
 
 target_compile_options(test_sana2_device PRIVATE

tests/sana2/host/test_sana2_device_host.c

@@ -1810,6 +1810,14 @@ static void case_bursty_wifi_reads(void)
     h_check(ami_sana2_default_ip_reads(NULL) == 0,
             "an unnamed driver keeps the ordinary BPS ladder");
 
+    h_check(ami_sana2_default_tcp_ack_max("DEVS:Networks/anxwifipi.device") == 11680UL,
+            "the shipped WiFiPi driver gets the measured ACK ceiling");
+    h_check(ami_sana2_default_tcp_ack_max("WIFIPI.DEVICE") == 11680UL,
+            "the upstream WiFiPi name gets the same ceiling");
+    h_check(ami_sana2_default_tcp_ack_max("genet.device") == 0 &&
+            ami_sana2_default_tcp_ack_max(NULL) == 0,
+            "wired and unnamed drivers keep the port ACK ceiling");
+
     /* The DEVICE= lines Install-AmiNetXDuo writes for Wi-Fi, system layout
        and self-contained drawer: neither carries IPREQUESTS. */
     h_check(ami_sana2_default_ip_reads("DEVS:Networks/anxwifipi.device") == 128 &&

tools/check-image-size.sh

@@ -71,7 +71,10 @@ BUDGETS=(
     # 364,664 with the bounded S2_OFFLINE: timer-bounded reply wait, abort,
     # and an abandoned request kept with its interface until the device
     # replies (#90, 5473e26e), 2026-09-26 (micro 204,052, minimal 238,240).
-    "default:src/bsdsocket/bsdsocket.library:365000"
+    # 365,468 with per-interface TCP ACK policy (#109): config parsing and
+    # publishing the WiFi/default-or-explicit ceiling into each NX_INTERFACE.
+    # This adds 468 bytes over the previous resident-image budget.
+    "default:src/bsdsocket/bsdsocket.library:366000"
     # 41,412 after stateless receive-checksum verification was added to the
     # EL3 and word/long NE2000 direct paths, 2026-09-15.  43,620 with
     # ANXD_CMD_RX_BATCH in the shell (claim, completion, staging copy, the