misc

12 files changed, 492 insertions, 72 deletions

diff --git a/lib9p/include/lib9p/_types.h b/lib9p/include/lib9p/_types.h
index 7f320a5..94accc0 100644
--- a/lib9p/include/lib9p/_types.h
+++ b/lib9p/include/lib9p/_types.h
@@ -8,13 +8,15 @@
 /* versions *******************************************************************/
 
 enum lib9p_version {
-	LIB9P_VER_UNINITIALIZED = 0,
-	LIB9P_VER_9P2000,   /* "9P2000" */
-	LIB9P_VER_9P2000_e, /* "9P2000.e" */
-	LIB9P_VER_9P2000_u, /* "9P2000.u" */
+	LIB9P_VER_unknown = 0, /* "unknown" */
+	LIB9P_VER_9P2000,      /* "9P2000" */
+	LIB9P_VER_9P2000_e,    /* "9P2000.e" */
+	LIB9P_VER_9P2000_u,    /* "9P2000.u" */
 	LIB9P_VER_NUM,
 };
 
+const char *lib9p_version_str(enum lib9p_version);
+
 /* non-message structs ********************************************************/
 
 struct lib9p_d {
@@ -90,40 +92,7 @@ enum lib9p_msg_type { /* uint8_t */
 	LIB9P_TYP_Rswrite  = 155, /* 9P2000.e */
 };
 
-#define LIB9P_TYPECODE_FOR_CTYPE(msg) _Generic((msg), \
-		struct lib9p_msg_Tversion: LIB9P_TYP_Tversion, \
-		struct lib9p_msg_Rversion: LIB9P_TYP_Rversion, \
-		struct lib9p_msg_Tauth: LIB9P_TYP_Tauth, \
-		struct lib9p_msg_Rauth: LIB9P_TYP_Rauth, \
-		struct lib9p_msg_Tattach: LIB9P_TYP_Tattach, \
-		struct lib9p_msg_Rattach: LIB9P_TYP_Rattach, \
-		struct lib9p_msg_Rerror: LIB9P_TYP_Rerror, \
-		struct lib9p_msg_Tflush: LIB9P_TYP_Tflush, \
-		struct lib9p_msg_Rflush: LIB9P_TYP_Rflush, \
-		struct lib9p_msg_Twalk: LIB9P_TYP_Twalk, \
-		struct lib9p_msg_Rwalk: LIB9P_TYP_Rwalk, \
-		struct lib9p_msg_Topen: LIB9P_TYP_Topen, \
-		struct lib9p_msg_Ropen: LIB9P_TYP_Ropen, \
-		struct lib9p_msg_Tcreate: LIB9P_TYP_Tcreate, \
-		struct lib9p_msg_Rcreate: LIB9P_TYP_Rcreate, \
-		struct lib9p_msg_Tread: LIB9P_TYP_Tread, \
-		struct lib9p_msg_Rread: LIB9P_TYP_Rread, \
-		struct lib9p_msg_Twrite: LIB9P_TYP_Twrite, \
-		struct lib9p_msg_Rwrite: LIB9P_TYP_Rwrite, \
-		struct lib9p_msg_Tclunk: LIB9P_TYP_Tclunk, \
-		struct lib9p_msg_Rclunk: LIB9P_TYP_Rclunk, \
-		struct lib9p_msg_Tremove: LIB9P_TYP_Tremove, \
-		struct lib9p_msg_Rremove: LIB9P_TYP_Rremove, \
-		struct lib9p_msg_Tstat: LIB9P_TYP_Tstat, \
-		struct lib9p_msg_Rstat: LIB9P_TYP_Rstat, \
-		struct lib9p_msg_Twstat: LIB9P_TYP_Twstat, \
-		struct lib9p_msg_Rwstat: LIB9P_TYP_Rwstat, \
-		struct lib9p_msg_Tsession: LIB9P_TYP_Tsession, \
-		struct lib9p_msg_Rsession: LIB9P_TYP_Rsession, \
-		struct lib9p_msg_Tsread: LIB9P_TYP_Tsread, \
-		struct lib9p_msg_Rsread: LIB9P_TYP_Rsread, \
-		struct lib9p_msg_Tswrite: LIB9P_TYP_Tswrite, \
-		struct lib9p_msg_Rswrite: LIB9P_TYP_Rswrite)
+const char *lib9p_msg_type_str(enum lib9p_msg_type);
 
 struct lib9p_msg_Tversion {
 	uint32_t         max_msg_size;
diff --git a/lib9p/include/lib9p/srv.h b/lib9p/include/lib9p/srv.h
index a8bd9c7..3ca8b4d 100644
--- a/lib9p/include/lib9p/srv.h
+++ b/lib9p/include/lib9p/srv.h
@@ -4,13 +4,23 @@
 #include <libcr/coroutine.h>
 #include <libcr_ipc/chan.h>
 
-struct lib9p_srvreq;
+struct lib9p_srv_req;
 
 struct lib9p_srv {
 	int                                     sockfd;
-	cr_chan_t(struct lib9p_srvreq *)        reqch;
+
+	cr_chan_t(struct lib9p_srv_req *)       reqch;
 };
 
+/**
+ * Will just close the connection if a T-message has a size[4] <7.
+ * @errno LINUX_EMSGSIZE T-message has size[4] bigger than max_msg_size
+ * @errno LINUX_EDOM Tversion specified an impossibly small max_msg_size
+ * @errno LINUX_EOPNOTSUPP T-message has an R-message type, or an unrecognized T-message type
+ * @errno LINUX_EBADMSG T-message has wrong size[4] for its content, or has invalid UTF-8
+ * @errno LINUX_ERANGE R-message does not fit into max_msg_size
+ */
+
 COROUTINE lib9p_srv_read_cr(void *_srv);
 COROUTINE lib9p_srv_write_cr(void *_srv);
 
diff --git a/lib9p/internal.h b/lib9p/internal.h
index a5175af..08bb462 100644
--- a/lib9p/internal.h
+++ b/lib9p/internal.h
@@ -51,6 +51,7 @@ struct _checksize_ctx {
 	 * "extra" beyond sizeof().  */
 	size_t	                 host_extra;
 };
+typedef bool (*_checksize_fn_t)(struct _checksize_ctx *ctx);
 
 struct _unmarshal_ctx {
 	struct lib9p_ctx        *ctx;
@@ -60,6 +61,7 @@ struct _unmarshal_ctx {
 	/* `extra` points to the beginning of unallocated space.  */
 	void                    *extra;
 };
+typedef void (*_unmarshal_fn_t)(struct _unmarshal_ctx *ctx, void *out);
 
 struct _marshal_ctx {
 	struct lib9p_ctx        *ctx;
@@ -67,9 +69,6 @@ struct _marshal_ctx {
 	uint8_t                 *net_bytes;
 	uint32_t                 net_offset;
 };
-
-typedef bool (*_checksize_fn_t)(struct _checksize_ctx *ctx);
-typedef void (*_unmarshal_fn_t)(struct _unmarshal_ctx *ctx, void *out);
 typedef bool (*_marshal_fn_t)(struct _marshal_ctx *ctx, void *host_val);
 
 struct _vtable_msg {
diff --git a/lib9p/srv.c b/lib9p/srv.c
index 039b4c2..74c2014 100644
--- a/lib9p/srv.c
+++ b/lib9p/srv.c
@@ -10,18 +10,24 @@
 #include <lib9p/srv.h>
 #include "internal.h"
 
-struct lib9p_srvconn {
+/* The hierarchy of concepts is:
+ *
+ *     server -> connection -> session -> request
+ *
+ */
+
+struct lib9p_srv_sess {
 	/* immutable */
 	struct lib9p_srv        *srv;
-	cid_t                    reader;
-	int                      fd;
+	int                      connfd;
+	cid_t                    reader; /* the lib9p_srv_read_cr() coroutine for this session */
 	/* mutable */
 	struct lib9p_ctx         ctx;
 	unsigned int             refcount;
 };
 
-struct lib9p_srvreq {
-	struct lib9p_srvconn    *conn;
+struct lib9p_srv_req {
+	struct lib9p_srv_sess   *sess;
 	uint8_t                 *msg;
 };
 
@@ -79,7 +85,7 @@ COROUTINE lib9p_srv_read_cr(void *_srv) {
 			}
 			goal = decode_u32le(buf);
 			if (goal < 7) {
-				/* We can't respond with an Rerror becuase we wouldn't know what tag to use!  */ 
+				/* We can't even respond with an Rerror becuase we wouldn't know what tag to use!  */ 
 				fprintf(stderr, "error: T-message is impossibly small");
 				goto close;
 			}
@@ -184,5 +190,42 @@ void handle_message(struct lib9p_srvconn *conn, uint8_t *net) {
 	netio_write(req.conn->fd, net, decode_u32le(net));
 }
 
-// EMSGSIZE for request too large
-// EPROTONOSUPPORT for version errors
+void _version(struct lib9p_srv_req *ctx, struct lib9p_msg_Tversion *req, struct lib9p_msg_Rversion *resp) {
+	enum lib9p_version version = LIB9P_VER_unknown;
+
+	if (req->version.len >= 6 &&
+	    req->version.utf8[0] == '9' && 
+	    req->version.utf8[1] == 'P' && 
+	    '0' <= req->version.utf8[2] && req->version.utf8[2] <= '9' &&
+	    '0' <= req->version.utf8[3] && req->version.utf8[3] <= '9' &&
+	    '0' <= req->version.utf8[4] && req->version.utf8[4] <= '9' &&
+	    '0' <= req->version.utf8[5] && req->version.utf8[5] <= '9' &&
+	    (req->version.utf8[6] == '\0' || req->version.utf8[6] == '.')) {
+		if (strcmp(&req->version.utf8[6], ".u") == 0)
+			version = LIB9P_VER_9P2000_u;
+		//else if (strcmp(&req->version.utf8[6], ".e") == 0)
+		//	version = LIB9P_VER_9P2000_e;
+		else
+			version = LIB9P_VER_9P2000;
+	}
+
+	struct lib9p_ctx empty_ctx = {
+		.version      = version,
+		.max_msg_size = CONFIG_9P_MAX_MSG_SIZE,
+	};
+	struct lib9p_msg_Rerror empty_error = { 0 };
+	assert(!lib9p_marshal(&empty_ctx, LIB9P_TYP_Rerror, 0, &empty_error, ctx->net));
+	uint32_t min_msg_size = decode_u32le(ctx->net);
+	assert(CONFIG_9P_MAX_MSG_SIZE >= min_msg_size);
+
+	if (req->max_msg_size < min_msg_size) {
+		lib9p_errorf(&ctx->ctx, LINUX_EDOM, "requested max_msg_size is less than minimum for %s (%"PRIu32" < %"PRIu32")",
+		             version, req->max_msg_size, min_msg_size);
+		return;
+	}
+
+	resp->version = lib9p_version_str(version);
+	resp->max_msg_size = (CONFIG_9P_MAX_MSG_SIZE < req->max_msg_size)
+		? CONFIG_9P_MAX_MSG_SIZE
+		: req->max_msg_size;
+}
diff --git a/lib9p/types.c b/lib9p/types.c
index 91a503d..8a48b85 100644
--- a/lib9p/types.c
+++ b/lib9p/types.c
@@ -1,5 +1,6 @@
 /* Generated by `./lib9p/types.gen lib9p/9P2000.txt lib9p/9P2000.u.txt lib9p/9P2000.e.txt`.  DO NOT EDIT!  */
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stddef.h>   /* for size_t */
 #include <inttypes.h> /* for PRI* macros */
@@ -9,6 +10,284 @@
 
 #include "internal.h"
 
+/* strings ********************************************************************/
+
+static const char *version_strs[LIB9P_VER_NUM] = {
+	[LIB9P_VER_unknown] = "unknown",
+	[LIB9P_VER_9P2000] = "9P2000",
+	[LIB9P_VER_9P2000_e] = "9P2000.e",
+	[LIB9P_VER_9P2000_u] = "9P2000.u",
+};
+
+const char *lib9p_version_str(enum lib9p_version ver) {
+    assert(0 <= ver && ver < LIB9P_VER_NUM);
+    return version_strs[ver];
+}
+
+static const char *msg_type_strs[0xFF] = {
+	[0x00] = "0x00",
+	[0x01] = "0x01",
+	[0x02] = "0x02",
+	[0x03] = "0x03",
+	[0x04] = "0x04",
+	[0x05] = "0x05",
+	[0x06] = "0x06",
+	[0x07] = "0x07",
+	[0x08] = "0x08",
+	[0x09] = "0x09",
+	[0x0A] = "0x0A",
+	[0x0B] = "0x0B",
+	[0x0C] = "0x0C",
+	[0x0D] = "0x0D",
+	[0x0E] = "0x0E",
+	[0x0F] = "0x0F",
+	[0x10] = "0x10",
+	[0x11] = "0x11",
+	[0x12] = "0x12",
+	[0x13] = "0x13",
+	[0x14] = "0x14",
+	[0x15] = "0x15",
+	[0x16] = "0x16",
+	[0x17] = "0x17",
+	[0x18] = "0x18",
+	[0x19] = "0x19",
+	[0x1A] = "0x1A",
+	[0x1B] = "0x1B",
+	[0x1C] = "0x1C",
+	[0x1D] = "0x1D",
+	[0x1E] = "0x1E",
+	[0x1F] = "0x1F",
+	[0x20] = "0x20",
+	[0x21] = "0x21",
+	[0x22] = "0x22",
+	[0x23] = "0x23",
+	[0x24] = "0x24",
+	[0x25] = "0x25",
+	[0x26] = "0x26",
+	[0x27] = "0x27",
+	[0x28] = "0x28",
+	[0x29] = "0x29",
+	[0x2A] = "0x2A",
+	[0x2B] = "0x2B",
+	[0x2C] = "0x2C",
+	[0x2D] = "0x2D",
+	[0x2E] = "0x2E",
+	[0x2F] = "0x2F",
+	[0x30] = "0x30",
+	[0x31] = "0x31",
+	[0x32] = "0x32",
+	[0x33] = "0x33",
+	[0x34] = "0x34",
+	[0x35] = "0x35",
+	[0x36] = "0x36",
+	[0x37] = "0x37",
+	[0x38] = "0x38",
+	[0x39] = "0x39",
+	[0x3A] = "0x3A",
+	[0x3B] = "0x3B",
+	[0x3C] = "0x3C",
+	[0x3D] = "0x3D",
+	[0x3E] = "0x3E",
+	[0x3F] = "0x3F",
+	[0x40] = "0x40",
+	[0x41] = "0x41",
+	[0x42] = "0x42",
+	[0x43] = "0x43",
+	[0x44] = "0x44",
+	[0x45] = "0x45",
+	[0x46] = "0x46",
+	[0x47] = "0x47",
+	[0x48] = "0x48",
+	[0x49] = "0x49",
+	[0x4A] = "0x4A",
+	[0x4B] = "0x4B",
+	[0x4C] = "0x4C",
+	[0x4D] = "0x4D",
+	[0x4E] = "0x4E",
+	[0x4F] = "0x4F",
+	[0x50] = "0x50",
+	[0x51] = "0x51",
+	[0x52] = "0x52",
+	[0x53] = "0x53",
+	[0x54] = "0x54",
+	[0x55] = "0x55",
+	[0x56] = "0x56",
+	[0x57] = "0x57",
+	[0x58] = "0x58",
+	[0x59] = "0x59",
+	[0x5A] = "0x5A",
+	[0x5B] = "0x5B",
+	[0x5C] = "0x5C",
+	[0x5D] = "0x5D",
+	[0x5E] = "0x5E",
+	[0x5F] = "0x5F",
+	[0x60] = "0x60",
+	[0x61] = "0x61",
+	[0x62] = "0x62",
+	[0x63] = "0x63",
+	[0x64] = "Tversion",
+	[0x65] = "Rversion",
+	[0x66] = "Tauth",
+	[0x67] = "Rauth",
+	[0x68] = "Tattach",
+	[0x69] = "Rattach",
+	[0x6A] = "0x6A",
+	[0x6B] = "Rerror",
+	[0x6C] = "Tflush",
+	[0x6D] = "Rflush",
+	[0x6E] = "Twalk",
+	[0x6F] = "Rwalk",
+	[0x70] = "Topen",
+	[0x71] = "Ropen",
+	[0x72] = "Tcreate",
+	[0x73] = "Rcreate",
+	[0x74] = "Tread",
+	[0x75] = "Rread",
+	[0x76] = "Twrite",
+	[0x77] = "Rwrite",
+	[0x78] = "Tclunk",
+	[0x79] = "Rclunk",
+	[0x7A] = "Tremove",
+	[0x7B] = "Rremove",
+	[0x7C] = "Tstat",
+	[0x7D] = "Rstat",
+	[0x7E] = "Twstat",
+	[0x7F] = "Rwstat",
+	[0x80] = "0x80",
+	[0x81] = "0x81",
+	[0x82] = "0x82",
+	[0x83] = "0x83",
+	[0x84] = "0x84",
+	[0x85] = "0x85",
+	[0x86] = "0x86",
+	[0x87] = "0x87",
+	[0x88] = "0x88",
+	[0x89] = "0x89",
+	[0x8A] = "0x8A",
+	[0x8B] = "0x8B",
+	[0x8C] = "0x8C",
+	[0x8D] = "0x8D",
+	[0x8E] = "0x8E",
+	[0x8F] = "0x8F",
+	[0x90] = "0x90",
+	[0x91] = "0x91",
+	[0x92] = "0x92",
+	[0x93] = "0x93",
+	[0x94] = "0x94",
+	[0x95] = "0x95",
+	[0x96] = "Tsession",
+	[0x97] = "Rsession",
+	[0x98] = "Tsread",
+	[0x99] = "Rsread",
+	[0x9A] = "Tswrite",
+	[0x9B] = "Rswrite",
+	[0x9C] = "0x9C",
+	[0x9D] = "0x9D",
+	[0x9E] = "0x9E",
+	[0x9F] = "0x9F",
+	[0xA0] = "0xA0",
+	[0xA1] = "0xA1",
+	[0xA2] = "0xA2",
+	[0xA3] = "0xA3",
+	[0xA4] = "0xA4",
+	[0xA5] = "0xA5",
+	[0xA6] = "0xA6",
+	[0xA7] = "0xA7",
+	[0xA8] = "0xA8",
+	[0xA9] = "0xA9",
+	[0xAA] = "0xAA",
+	[0xAB] = "0xAB",
+	[0xAC] = "0xAC",
+	[0xAD] = "0xAD",
+	[0xAE] = "0xAE",
+	[0xAF] = "0xAF",
+	[0xB0] = "0xB0",
+	[0xB1] = "0xB1",
+	[0xB2] = "0xB2",
+	[0xB3] = "0xB3",
+	[0xB4] = "0xB4",
+	[0xB5] = "0xB5",
+	[0xB6] = "0xB6",
+	[0xB7] = "0xB7",
+	[0xB8] = "0xB8",
+	[0xB9] = "0xB9",
+	[0xBA] = "0xBA",
+	[0xBB] = "0xBB",
+	[0xBC] = "0xBC",
+	[0xBD] = "0xBD",
+	[0xBE] = "0xBE",
+	[0xBF] = "0xBF",
+	[0xC0] = "0xC0",
+	[0xC1] = "0xC1",
+	[0xC2] = "0xC2",
+	[0xC3] = "0xC3",
+	[0xC4] = "0xC4",
+	[0xC5] = "0xC5",
+	[0xC6] = "0xC6",
+	[0xC7] = "0xC7",
+	[0xC8] = "0xC8",
+	[0xC9] = "0xC9",
+	[0xCA] = "0xCA",
+	[0xCB] = "0xCB",
+	[0xCC] = "0xCC",
+	[0xCD] = "0xCD",
+	[0xCE] = "0xCE",
+	[0xCF] = "0xCF",
+	[0xD0] = "0xD0",
+	[0xD1] = "0xD1",
+	[0xD2] = "0xD2",
+	[0xD3] = "0xD3",
+	[0xD4] = "0xD4",
+	[0xD5] = "0xD5",
+	[0xD6] = "0xD6",
+	[0xD7] = "0xD7",
+	[0xD8] = "0xD8",
+	[0xD9] = "0xD9",
+	[0xDA] = "0xDA",
+	[0xDB] = "0xDB",
+	[0xDC] = "0xDC",
+	[0xDD] = "0xDD",
+	[0xDE] = "0xDE",
+	[0xDF] = "0xDF",
+	[0xE0] = "0xE0",
+	[0xE1] = "0xE1",
+	[0xE2] = "0xE2",
+	[0xE3] = "0xE3",
+	[0xE4] = "0xE4",
+	[0xE5] = "0xE5",
+	[0xE6] = "0xE6",
+	[0xE7] = "0xE7",
+	[0xE8] = "0xE8",
+	[0xE9] = "0xE9",
+	[0xEA] = "0xEA",
+	[0xEB] = "0xEB",
+	[0xEC] = "0xEC",
+	[0xED] = "0xED",
+	[0xEE] = "0xEE",
+	[0xEF] = "0xEF",
+	[0xF0] = "0xF0",
+	[0xF1] = "0xF1",
+	[0xF2] = "0xF2",
+	[0xF3] = "0xF3",
+	[0xF4] = "0xF4",
+	[0xF5] = "0xF5",
+	[0xF6] = "0xF6",
+	[0xF7] = "0xF7",
+	[0xF8] = "0xF8",
+	[0xF9] = "0xF9",
+	[0xFA] = "0xFA",
+	[0xFB] = "0xFB",
+	[0xFC] = "0xFC",
+	[0xFD] = "0xFD",
+	[0xFE] = "0xFE",
+	[0xFF] = "0xFF",
+};
+
+const char *lib9p_msg_type_str(enum lib9p_msg_type typ) {
+    assert(0 <= typ && typ <= 0xFF);
+    return msg_type_strs[typ];
+}
+
 /* checksize_* (internals of unmarshal_size()) ********************************/
 
 static inline bool _checksize_net(struct _checksize_ctx *ctx, uint32_t n) {
@@ -799,7 +1078,7 @@ static bool marshal_Rswrite(struct _marshal_ctx *ctx, struct lib9p_msg_Rswrite *
 	}
 
 struct _vtable_version _lib9p_vtables[LIB9P_VER_NUM] = {
-	[LIB9P_VER_UNINITIALIZED] = { .msgs = {
+	[LIB9P_VER_unknown] = { .msgs = {
 		_MSG(Tversion),
 		_MSG(Rversion),
 		_MSG(Rerror),
diff --git a/lib9p/types.gen b/lib9p/types.gen
index 15936e7..590e707 100755
--- a/lib9p/types.gen
+++ b/lib9p/types.gen
@@ -241,14 +241,16 @@ def gen_h(idprefix: str, versions: set[str], structs: list[Struct]) -> str:
 /* versions *******************************************************************/
 
 enum {idprefix}version {{
-	{idprefix.upper()}VER_UNINITIALIZED = 0,
 """
-    verwidth = max(len(v) for v in versions)
-    for ver in sorted(versions):
+    fullversions = ["unknown = 0", *sorted(versions)]
+    verwidth = max(len(v) for v in fullversions)
+    for ver in fullversions:
         ret += f"\t{c_verenum(idprefix, ver)},"
-        ret += (" " * (verwidth - len(ver))) + ' /* "' + ver + '" */\n'
-    ret += f"\t{idprefix.upper()}VER_NUM,\n"
+        ret += (" " * (verwidth - len(ver))) + ' /* "' + ver.split()[0] + '" */\n'
+    ret += f"\t{c_verenum(idprefix, 'NUM')},\n"
     ret += "};\n"
+    ret += "\n"
+    ret += f"const char *{idprefix}version_str(enum {idprefix}version);\n"
 
     ret += """
 /* non-message structs ********************************************************/
@@ -287,16 +289,8 @@ enum {idprefix}version {{
             ret += " " + comment
         ret += "\n"
     ret += "};\n"
-
     ret += "\n"
-    ret += f"#define {idprefix.upper()}TYPECODE_FOR_CTYPE(msg) _Generic((msg)"
-    for msg in structs:
-        if msg.msgid is None:
-            continue
-        ret += (
-            f", \\\n\t\t{c_typename(idprefix, msg)}: {idprefix.upper()}TYP_{msg.name}"
-        )
-    ret += ")\n"
+    ret += f"const char *{idprefix}msg_type_str(enum {idprefix}msg_type);\n"
 
     for msg in structs:
         if msg.msgid is None:
@@ -333,6 +327,7 @@ enum {idprefix}version {{
 def gen_c(idprefix: str, versions: set[str], structs: list[Struct]) -> str:
     ret = f"""/* Generated by `{' '.join(sys.argv)}`.  DO NOT EDIT!  */
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stddef.h>   /* for size_t */
 #include <inttypes.h> /* for PRI* macros */
@@ -349,6 +344,37 @@ def gen_c(idprefix: str, versions: set[str], structs: list[Struct]) -> str:
     def unused(arg: str) -> str:
         return f"UNUSED({arg})"
 
+    # strings ##################################################################
+    ret += f"""
+/* strings ********************************************************************/
+
+static const char *version_strs[{c_verenum(idprefix, 'NUM')}] = {{
+"""
+    for ver in ["unknown", *sorted(versions)]:
+        ret += f'\t[{c_verenum(idprefix, ver)}] = "{ver}",\n'
+    ret += "};\n"
+    ret += f"""
+const char *{idprefix}version_str(enum {idprefix}version ver) {{
+    assert(0 <= ver && ver < {c_verenum(idprefix, 'NUM')});
+    return version_strs[ver];
+}}
+
+static const char *msg_type_strs[0xFF] = {{
+"""
+    id2name: dict[int, str] = {}
+    for msg in structs:
+        if msg.msgid is not None:
+            id2name[msg.msgid] = msg.name
+    for n in range(0, 0x100):
+        ret += '\t[0x{:02X}] = "{}",\n'.format(n, id2name.get(n, "0x{:02X}".format(n)))
+    ret += "};\n"
+    ret += f"""
+const char *{idprefix}msg_type_str(enum {idprefix}msg_type typ) {{
+    assert(0 <= typ && typ <= 0xFF);
+    return msg_type_strs[typ];
+}}
+"""
+
     # checksize_* ##############################################################
     ret += """
 /* checksize_* (internals of unmarshal_size()) ********************************/
@@ -591,10 +617,10 @@ static inline bool marshal_8(struct _marshal_ctx *ctx, uint64_t *val) {
 		.marshal             = (_marshal_fn_t)marshal_##typ,       \\
 	}}
 
-struct _vtable_version _{idprefix}vtables[LIB9P_VER_NUM] = {{
+struct _vtable_version _{idprefix}vtables[{c_verenum(idprefix, 'NUM')}] = {{
 """
 
-    ret += f"\t[{idprefix.upper()}VER_UNINITIALIZED] = {{ .msgs = {{\n"
+    ret += f"\t[{c_verenum(idprefix, 'unknown')}] = {{ .msgs = {{\n"
     for msg in structs:
         if msg.name in ["Tversion", "Rversion", "Rerror"]:  # SPECIAL
             ret += f"\t\t_MSG({msg.name}),\n"
diff --git a/libcr_ipc/CMakeLists.txt b/libcr_ipc/CMakeLists.txt
index 3388fcd..957b638 100644
--- a/libcr_ipc/CMakeLists.txt
+++ b/libcr_ipc/CMakeLists.txt
@@ -7,6 +7,7 @@ add_library(libcr_ipc INTERFACE)
 target_include_directories(libcr_ipc SYSTEM INTERFACE ${CMAKE_CURRENT_LIST_DIR}/include)
 target_sources(libcr_ipc INTERFACE
 	sema.c
+	mutex.c
 )
 target_link_libraries(libcr_ipc INTERFACE
 	libcr
diff --git a/libcr_ipc/include/libcr_ipc/mutex.h b/libcr_ipc/include/libcr_ipc/mutex.h
new file mode 100644
index 0000000..38ebde0
--- /dev/null
+++ b/libcr_ipc/include/libcr_ipc/mutex.h
@@ -0,0 +1,46 @@
+/* libcr_ipc/mutex.h - Simple mutexes for libcr (header file)
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-Licence-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _COROUTINE_MUTEX_H_
+#define _COROUTINE_MUTEX_H_
+
+#include <stdbool.h> /* for bool */
+
+#include <libcr/coroutine.h> /* for cid_t */
+
+struct _cr_mutex_cid_list {
+	cid_t                            val;
+	struct _cr_mutex_cid_list        *next;
+};
+
+/**
+ * A cr_mutex_t is a fair mutex.
+ */
+typedef struct {
+	bool                             locked;
+	struct _cr_mutex_cid_list        *head, **tail;
+} cr_mutex_t;
+
+/**
+ * Lock the mutex.  Blocks if it is already locked.
+ *
+ * @blocks maybe
+ * @yields maybe
+ * @run_in coroutine
+ */
+void cr_mutex_lock(cr_mutex_t *);
+
+/**
+ * Unlock the mutex.  Unblocks a coroutine that is blocked on
+ * cr_mutex_lock().
+ *
+ * @blocks never
+ * @yields never
+ * @may_run_in coroutine
+ */
+void cr_mutex_unluck(cr_mutex_t *);
+
+#endif /* _COROUTINE_MUTEX_H_ */
diff --git a/libcr_ipc/include/libcr_ipc/sema.h b/libcr_ipc/include/libcr_ipc/sema.h
index a2a176d..454eb5d 100644
--- a/libcr_ipc/include/libcr_ipc/sema.h
+++ b/libcr_ipc/include/libcr_ipc/sema.h
@@ -1,4 +1,4 @@
-/* coroutine_sema.h - Simple semaphores for coroutine.{h,c}
+/* libcr_ipc/sema.h - Simple semaphores for libcr (header file)
  *
  * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-Licence-Identifier: AGPL-3.0-or-later
@@ -7,6 +7,10 @@
 #ifndef _COROUTINE_SEMA_H_
 #define _COROUTINE_SEMA_H_
 
+#include <stdbool.h> /* for bool */
+
+#include <libcr/coroutine.h> /* for cid_t */
+
 struct _cr_sema_cid_list {
 	cid_t                            val;
 	struct _cr_sema_cid_list        *next;
diff --git a/libcr_ipc/mutex.c b/libcr_ipc/mutex.c
new file mode 100644
index 0000000..c5cea96
--- /dev/null
+++ b/libcr_ipc/mutex.c
@@ -0,0 +1,37 @@
+/* libcr_ipc/mutex.c - Simple mutexes for libcr (implementation file)
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-Licence-Identifier: AGPL-3.0-or-later
+ */
+
+#include <libcr_ipc/mutex.h>
+
+void cr_mutex_lock(cr_mutex_t *mu) {
+	assert(mu);
+	if (!mu->tail)
+		mu->tail = &mu->head;
+	if (!mu->locked) {
+		mu->locked = true;
+		return;
+	}
+	struct _cr_mutex_cid_list self = {
+		.val = cr_getcid(),
+		.next = NULL,
+	};
+	*(mu->tail) = &self;
+	mu->tail = &(self.next);
+	cr_pause_and_yield();
+}
+
+void cr_mutex_unlock(cr_mutex_t *mu) {
+	assert(mu);
+	assert(mu->tail);
+	assert(mu->locked);
+	if (mu->head) {
+		cr_unpause(mu->head->val);
+		mu->head = mu->head->next;
+		if (!mu->head)
+			mu->tail = &mu->head;
+	} else
+		mu->locked = false;
+}
diff --git a/libcr_ipc/sema.c b/libcr_ipc/sema.c
index a3b2ca0..9645a41 100644
--- a/libcr_ipc/sema.c
+++ b/libcr_ipc/sema.c
@@ -1,4 +1,4 @@
-/* coroutine_sema.h - Simple semaphores for coroutine.{h,c}
+/* libcr_ipc/sema.c - Simple semaphores for libcr (implementation file)
  *
  * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-Licence-Identifier: AGPL-3.0-or-later
@@ -6,7 +6,6 @@
 
 #include <assert.h>
 
-#include <libcr/coroutine.h>
 #include <libcr_ipc/sema.h>
 
 /** Drain the sema->{head,tail} list.  Returns true if cr_getcid() was drained.  */
diff --git a/libnetio/include/libnetio/netio.h b/libnetio/include/libnetio/netio.h
index 9383c54..370d2ca 100644
--- a/libnetio/include/libnetio/netio.h
+++ b/libnetio/include/libnetio/netio.h
@@ -12,7 +12,14 @@ int netio_listen(uint16_t port);
 int netio_accept(int sock);
 /** Return bytes-read on success, 0 on EOF, -errno on error; a short read is *not* an error.  */
 ssize_t netio_read(int conn, void *buf, size_t count);
-/** Return `count` on success, -errno on error; a short write *is* an error.  */
+/**
+ * Return `count` on success, -errno on error; a short write *is* an
+ * error.
+ *
+ * Writes are *not* guaranteed to be atomic (as this would be
+ * expensive to implement), so if you have concurrent writers then you
+ * should arrange for a mutex to protect the connection.
+ */
 ssize_t netio_write(int conn, void *buf, size_t count);
 /** Return 0 on success, -errno on error.  */
 int netio_close(int conn, bool rd, bool wr);