First commitHEADmaster

17 files changed, 692 insertions, 0 deletions

diff --git a/src/protocol/CMakeLists.txt b/src/protocol/CMakeLists.txt
new file mode 100644
index 0000000..194274d
--- /dev/null
+++ b/src/protocol/CMakeLists.txt
@@ -0,0 +1,10 @@
+# wip, a small TCP/IP stack.
+# Copyright (C) 2025  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+add_subdirectory(icmp)
+add_subdirectory(tcp)
+add_subdirectory(udp)
diff --git a/src/protocol/icmp/CMakeLists.txt b/src/protocol/icmp/CMakeLists.txt
new file mode 100644
index 0000000..4fd374d
--- /dev/null
+++ b/src/protocol/icmp/CMakeLists.txt
@@ -0,0 +1,14 @@
+# wip, a small TCP/IP stack.
+# Copyright (C) 2025  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    alloc.c
+    free.c
+    rx.c
+    start.c
+    tx.c
+)
diff --git a/src/protocol/icmp/alloc.c b/src/protocol/icmp/alloc.c
new file mode 100644
index 0000000..23d7329
--- /dev/null
+++ b/src/protocol/icmp/alloc.c
@@ -0,0 +1,29 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/icmp.h>
+#include <wip/prv/icmp/routines.h>
+#include <wip/prv/icmp/types.h>
+#include <stddef.h>
+
+void *wip_icmp_alloc(struct wip *const w)
+{
+    const struct wip_cfg *const cfg = &w->cfg;
+    const struct wip_icmp z = {0};
+    struct wip_icmp *const ret = cfg->alloc(sizeof *ret, cfg->user);
+
+    if (!ret)
+        return ret;
+
+    *ret = z;
+    ret->next = wip_icmp_rx_start;
+    return ret;
+}
diff --git a/src/protocol/icmp/free.c b/src/protocol/icmp/free.c
new file mode 100644
index 0000000..452e1d4
--- /dev/null
+++ b/src/protocol/icmp/free.c
@@ -0,0 +1,25 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/icmp.h>
+#include <wip/prv/icmp/types.h>
+#include <stddef.h>
+
+void wip_icmp_free(struct wip *const w, void *const args)
+{
+    const struct wip_cfg *const cfg = &w->cfg;
+    struct wip_icmp *const icmp = args;
+
+    if (icmp)
+        cfg->free(icmp->buf, cfg->user);
+
+    cfg->free(icmp, cfg->user);
+}
diff --git a/src/protocol/icmp/rx.c b/src/protocol/icmp/rx.c
new file mode 100644
index 0000000..8e543f9
--- /dev/null
+++ b/src/protocol/icmp/rx.c
@@ -0,0 +1,200 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/io.h>
+#include <wip/prv/log.h>
+#include <wip/prv/icmp.h>
+#include <wip/prv/icmp/types.h>
+#include <stddef.h>
+#include <string.h>
+
+enum
+{
+    TYPE,
+    CHECKSUM = 2,
+    ID = 4,
+    SEQ_NUM = 6,
+    DATA = 8
+};
+
+#if 0
+
+static int get_type(struct wip_icmp *const icmp,
+    const unsigned char *const p, const size_t n)
+{
+    unsigned char type;
+
+    if (icmp->read)
+        return 0;
+
+    type = p[0];
+
+    if (type != ECHO_REQUEST)
+        return -1;
+
+    wip_log("%s: got echo request\n");
+    icmp->type = type;
+    return 0;
+}
+
+static void get_checksum(struct wip_icmp *const icmp,
+    const unsigned char *const p, const size_t n)
+{
+    size_t off;
+    struct wip_be16 v;
+    enum {END = CHECKSUM + sizeof v};
+
+    if (icmp->read >= END || n < END - icmp->read)
+        return;
+
+    off = CHECKSUM - icmp->read;
+    v.v[0] = p[off];
+    v.v[1] = p[off + 1];
+    icmp->exp_checksum = wip_be16(&v);
+}
+
+static void get_id(struct wip_icmp *const icmp, const unsigned char *const p,
+    const size_t n)
+{
+    size_t off;
+    struct wip_be16 v;
+    enum {END = ID + sizeof v};
+
+    if (icmp->read >= END || n < END - icmp->read)
+        return;
+
+    off = ID - icmp->read;
+    v.v[0] = p[off];
+    v.v[1] = p[off + 1];
+    icmp->id = wip_be16(&v);
+}
+
+static void get_seqnum(struct wip_icmp *const icmp, const unsigned char *const p,
+    const size_t n)
+{
+    size_t off;
+    struct wip_be16 v;
+    enum {END = SEQ_NUM + sizeof v};
+
+    if (icmp->read >= END || n < END - icmp->read)
+        return;
+
+    off = SEQ_NUM - icmp->read;
+    v.v[0] = p[off];
+    v.v[1] = p[off + 1];
+    icmp->seqnum = wip_be16(&v);
+    wip_log("chksum=%#x, id=%#x, seq_num=%#x\n", icmp->exp_checksum,
+        icmp->id, icmp->seqnum);
+}
+
+static enum wip_state get_data(struct wip *const w,
+    struct wip_icmp *const icmp, const unsigned char *const p, const size_t n)
+{
+    const struct wip_cfg *const cfg = &w->cfg;
+    const size_t offset = icmp->read + n;
+    const void *src = p;
+    size_t sz = n;
+
+    if (offset < DATA)
+        return WIP_OK;
+    else if (!icmp->buf)
+    {
+        sz = n - DATA - icmp->read;
+        src = p + DATA - icmp->read;
+
+        if (!(icmp->buf = cfg->alloc(sz, cfg->user)))
+            return WIP_FATAL;
+    }
+    else
+    {
+        const size_t nsz = icmp->n + n;
+        enum {MAXSZ = 40};
+        void *buf;
+
+        if (nsz > MAXSZ)
+            return WIP_INVALID;
+        else if (!(buf = cfg->realloc(icmp->buf, nsz, cfg->user)))
+            return WIP_FATAL;
+
+        icmp->buf = buf;
+    }
+
+    memcpy((char *)icmp->buf + icmp->read, src, sz);
+    icmp->n += sz;
+
+    wip_log("data (%lu bytes): {", (unsigned long)icmp->n);
+
+    {
+        size_t i;
+
+        for (i = 0; i < icmp->n; i++)
+        {
+            wip_log("%#hhx", *((const char *)icmp->buf + i));
+
+            if (i + 1 < icmp->n)
+                wip_log(", ");
+        }
+    }
+
+    wip_log("}\n");
+    return WIP_OK;
+}
+#endif
+
+enum wip_state wip_icmp_rx(struct wip *const w, const void *buf,
+    size_t n, void *const args)
+{
+    struct wip_icmp *const icmp = args;
+    enum wip_state ret;
+    size_t r;
+
+    while ((ret = icmp->next(w, buf, n, icmp, &r)) == WIP_AGAIN)
+    {
+        buf = (const char *)buf + r;
+        n -= r;
+    }
+
+    return ret;
+
+#if 0
+    enum wip_state (*next)(struct wip *, const void *, size_t,
+        struct wip_icmp *)
+
+    const struct wip_rx_sm_h *const h = &w->rx.sm.h;
+    const unsigned char *const p = buf;
+    const unsigned short dlen = wip_be16(&h->len) - h->header_sz;
+
+    enum wip_state ret;
+    size_t i;
+
+    if (get_type(icmp, buf, n))
+        return 0;
+
+    get_checksum(icmp, buf, n);
+    get_id(icmp, buf, n);
+    get_seqnum(icmp, buf, n);
+
+    if ((ret = get_data(w, icmp, buf, n)))
+        return ret;
+
+    for (i = 0; i < n; i++)
+        /* Avoid suming checksum */
+        if (icmp->read >= CHECKSUM || ((i != 2) && (i != 3)))
+            icmp->checksum += p[i];
+
+    if (icmp->read += n >= dlen)
+    {
+        wip_log("expected checksum=%#x, got=%#x\n",
+            icmp->exp_checksum, icmp->checksum);
+    }
+
+    return WIP_OK;
+#endif
+}
diff --git a/src/protocol/icmp/start.c b/src/protocol/icmp/start.c
new file mode 100644
index 0000000..f50052e
--- /dev/null
+++ b/src/protocol/icmp/start.c
@@ -0,0 +1,205 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/io.h>
+#include <wip/prv/log.h>
+#include <wip/prv/icmp.h>
+#include <wip/prv/icmp/routines.h>
+#include <wip/prv/icmp/types.h>
+#include <stddef.h>
+#include <string.h>
+
+struct read
+{
+    const void *buf;
+    size_t n;
+    struct wip_icmp *icmp;
+};
+
+static int io_read(void *const buf, const size_t n, void *const user)
+{
+    const struct read *const r = user;
+    const size_t ret = n > r->n ? r->n : n;
+
+    memcpy(buf, r->buf, ret);
+    return ret;
+}
+
+static enum wip_state readbuf(struct wip_sm_io *const io, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp)
+{
+    struct wip_cfg cfg = {0};
+    struct read r;
+
+    r.buf = buf;
+    r.n = n;
+    r.icmp = icmp;
+
+    cfg.read = io_read;
+    cfg.user = &r;
+    return wip_io_read_c(&cfg, io);
+}
+
+enum wip_state get_payload(struct wip *const w, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp, size_t *const r)
+{
+    const struct wip_cfg *const cfg = &w->cfg;
+    const size_t nsz = icmp->read + n;
+    char *const nbuf = cfg->realloc(icmp->buf, nsz, cfg->user);
+    size_t i;
+
+    if (!nbuf)
+        return WIP_FATAL;
+
+    memcpy(nbuf + icmp->read, buf, n);
+    icmp->buf = nbuf;
+    icmp->read += n;
+    *r = n;
+
+    for (i = icmp->read; i < nsz; i++)
+        icmp->checksum += *(const char *)icmp->buf;
+
+    wip_log("ICMP data={");
+
+    for (i = 0; i < icmp->read; i++)
+    {
+        wip_log("%#hhx", *((const char *)icmp->buf + i));
+
+        if (i + 1 < icmp->read)
+            wip_log(", ");
+    }
+
+    wip_log("}\n");
+
+    wip_log("calculated checksum: %#hx, expected checksum: %#hx\n",
+        icmp->checksum, wip_be16(&icmp->exp_checksum));
+    return WIP_OK;
+}
+
+enum wip_state get_seqnum(struct wip *const w, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp, size_t *const r)
+{
+    const enum wip_state state = readbuf(&icmp->io, buf, n, icmp);
+
+    if (state)
+        return state;
+    else
+    {
+        struct wip_sm_io io = {0};
+
+        io.buf = &icmp->seqnum;
+        io.n = sizeof icmp->seqnum;
+        icmp->io = io;
+    }
+
+    wip_log("got seqnum: %#x\n", wip_be16(&icmp->seqnum));
+    icmp->checksum += wip_be16(&icmp->seqnum);
+    icmp->next = get_payload;
+    *r = sizeof icmp->seqnum;
+    return WIP_AGAIN;
+}
+
+enum wip_state get_id(struct wip *const w, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp, size_t *const r)
+{
+    const enum wip_state state = readbuf(&icmp->io, buf, n, icmp);
+
+    if (state)
+        return state;
+    else
+    {
+        struct wip_sm_io io = {0};
+
+        io.buf = &icmp->seqnum;
+        io.n = sizeof icmp->seqnum;
+        icmp->io = io;
+    }
+
+    wip_log("got id: %#x\n", wip_be16(&icmp->id));
+    icmp->checksum += wip_be16(&icmp->id);
+    icmp->next = get_seqnum;
+    *r = sizeof icmp->id;
+    return WIP_AGAIN;
+}
+
+enum wip_state get_checksum(struct wip *const w, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp, size_t *const r)
+{
+    const enum wip_state state = readbuf(&icmp->io, buf, n, icmp);
+
+    if (state)
+        return state;
+    else
+    {
+        struct wip_sm_io io = {0};
+
+        io.buf = &icmp->id;
+        io.n = sizeof icmp->id;
+        icmp->io = io;
+    }
+
+    wip_log("got expected checksum: %#x\n", wip_be16(&icmp->exp_checksum));
+    icmp->next = get_id;
+    *r = sizeof icmp->exp_checksum;
+    return WIP_AGAIN;
+}
+
+enum wip_state get_code(struct wip *const w, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp, size_t *const r)
+{
+    unsigned char code;
+    struct wip_sm_io io = {0};
+    enum wip_state state;
+
+    io.buf = &code;
+    io.n = sizeof code;
+
+    if ((state = readbuf(&io, buf, n, icmp)))
+        return state;
+    else if (code)
+        return WIP_INVALID;
+    else
+    {
+        struct wip_sm_io nio = {0};
+
+        nio.buf = &icmp->exp_checksum;
+        nio.n = sizeof icmp->exp_checksum;
+        icmp->io = nio;
+    }
+
+    wip_log("got code\n");
+    icmp->checksum += code;
+    icmp->next = get_checksum;
+    *r = sizeof code;
+    return WIP_AGAIN;
+}
+
+enum wip_state wip_icmp_rx_start(struct wip *const w, const void *const buf,
+    const size_t n, struct wip_icmp *const icmp, size_t *const r)
+{
+    unsigned char type;
+    struct wip_sm_io io = {0};
+    enum wip_state state;
+
+    io.buf = &type;
+    io.n = sizeof type;
+
+    if ((state = readbuf(&io, buf, n, icmp)))
+        return state;
+    else if (type != ICMP_ECHO_REQUEST)
+        return WIP_INVALID;
+
+    wip_log("got echo request\n");
+    icmp->checksum += type;
+    icmp->type = type;
+    icmp->next = get_code;
+    *r = sizeof type;
+    return WIP_AGAIN;
+}
diff --git a/src/protocol/icmp/tx.c b/src/protocol/icmp/tx.c
new file mode 100644
index 0000000..27fe876
--- /dev/null
+++ b/src/protocol/icmp/tx.c
@@ -0,0 +1,21 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/icmp.h>
+#include <wip/prv/icmp/types.h>
+#include <stddef.h>
+
+int wip_icmp_tx(struct wip *const wip, void *const buf, const size_t n,
+    void *const args)
+{
+    wip_log("%s: TODO\n");
+    return 0;
+}
diff --git a/src/protocol/tcp/CMakeLists.txt b/src/protocol/tcp/CMakeLists.txt
new file mode 100644
index 0000000..0caec18
--- /dev/null
+++ b/src/protocol/tcp/CMakeLists.txt
@@ -0,0 +1,13 @@
+# wip, a small TCP/IP stack.
+# Copyright (C) 2025  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    alloc.c
+    free.c
+    rx.c
+    tx.c
+)
diff --git a/src/protocol/tcp/alloc.c b/src/protocol/tcp/alloc.c
new file mode 100644
index 0000000..c90f1c9
--- /dev/null
+++ b/src/protocol/tcp/alloc.c
@@ -0,0 +1,20 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/tcp.h>
+#include <wip/prv/tcp/types.h>
+#include <stddef.h>
+
+void *wip_tcp_alloc(struct wip *const w)
+{
+    wip_log("%s: TODO\n", __func__);
+    return NULL;
+}
diff --git a/src/protocol/tcp/free.c b/src/protocol/tcp/free.c
new file mode 100644
index 0000000..ddde038
--- /dev/null
+++ b/src/protocol/tcp/free.c
@@ -0,0 +1,19 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/tcp.h>
+#include <wip/prv/tcp/types.h>
+#include <stddef.h>
+
+void wip_tcp_free(struct wip *const w, void *const args)
+{
+    wip_log("%s: TODO\n", __func__);
+}
diff --git a/src/protocol/tcp/rx.c b/src/protocol/tcp/rx.c
new file mode 100644
index 0000000..6b23546
--- /dev/null
+++ b/src/protocol/tcp/rx.c
@@ -0,0 +1,21 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/tcp.h>
+#include <wip/prv/tcp/types.h>
+#include <stddef.h>
+
+enum wip_state wip_tcp_rx(struct wip *const wip, const void *const buf,
+    const size_t n, void *const args)
+{
+    wip_log("%s: TODO\n");
+    return WIP_OK;
+}
diff --git a/src/protocol/tcp/tx.c b/src/protocol/tcp/tx.c
new file mode 100644
index 0000000..55524e3
--- /dev/null
+++ b/src/protocol/tcp/tx.c
@@ -0,0 +1,21 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/tcp.h>
+#include <wip/prv/tcp/types.h>
+#include <stddef.h>
+
+int wip_tcp_tx(struct wip *const wip, void *const buf, const size_t n,
+    void *const args)
+{
+    wip_log("%s: TODO\n");
+    return 0;
+}
diff --git a/src/protocol/udp/CMakeLists.txt b/src/protocol/udp/CMakeLists.txt
new file mode 100644
index 0000000..0caec18
--- /dev/null
+++ b/src/protocol/udp/CMakeLists.txt
@@ -0,0 +1,13 @@
+# wip, a small TCP/IP stack.
+# Copyright (C) 2025  Xavier Del Campo Romero
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+target_sources(${PROJECT_NAME} PRIVATE
+    alloc.c
+    free.c
+    rx.c
+    tx.c
+)
diff --git a/src/protocol/udp/alloc.c b/src/protocol/udp/alloc.c
new file mode 100644
index 0000000..d812ea5
--- /dev/null
+++ b/src/protocol/udp/alloc.c
@@ -0,0 +1,20 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/udp.h>
+#include <wip/prv/udp/types.h>
+#include <stddef.h>
+
+void *wip_udp_alloc(struct wip *const w)
+{
+    wip_log("%s: TODO\n", __func__);
+    return NULL;
+}
diff --git a/src/protocol/udp/free.c b/src/protocol/udp/free.c
new file mode 100644
index 0000000..c6354fb
--- /dev/null
+++ b/src/protocol/udp/free.c
@@ -0,0 +1,19 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/udp.h>
+#include <wip/prv/udp/types.h>
+#include <stddef.h>
+
+void wip_udp_free(struct wip *const w, void *const args)
+{
+    wip_log("%s: TODO\n", __func__);
+}
diff --git a/src/protocol/udp/rx.c b/src/protocol/udp/rx.c
new file mode 100644
index 0000000..29aa4cc
--- /dev/null
+++ b/src/protocol/udp/rx.c
@@ -0,0 +1,21 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/udp.h>
+#include <wip/prv/udp/types.h>
+#include <stddef.h>
+
+enum wip_state wip_udp_rx(struct wip *const wip, const void *const buf,
+    const size_t n, void *const args)
+{
+    wip_log("%s: TODO\n");
+    return WIP_OK;
+}
diff --git a/src/protocol/udp/tx.c b/src/protocol/udp/tx.c
new file mode 100644
index 0000000..a29ec0f
--- /dev/null
+++ b/src/protocol/udp/tx.c
@@ -0,0 +1,21 @@
+/*
+ * wip, a small TCP/IP stack.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <wip/wip.h>
+#include <wip/prv/log.h>
+#include <wip/prv/udp.h>
+#include <wip/prv/udp/types.h>
+#include <stddef.h>
+
+int wip_udp_tx(struct wip *const wip, void *const buf, const size_t n,
+    void *const args)
+{
+    wip_log("%s: TODO\n");
+    return 0;
+}