[FIX] Calculate correctly max payload size per UDP packet

apps/srt-file-transmit.cpp

@@ -180,7 +180,7 @@ int parse_args(FileTransmitConfig &cfg, int argc, char** argv)
         return 2;
     }
 
-    cfg.chunk_size    = stoul(Option<OutString>(params, "1456", o_chunk));
+    cfg.chunk_size    = stoul(Option<OutString>(params, "0", o_chunk));
     cfg.skip_flushing = Option<OutBool>(params, false, o_no_flush);
     cfg.bw_report     = stoi(Option<OutString>(params, "0", o_bwreport));
     cfg.stats_report  = stoi(Option<OutString>(params, "0", o_statsrep));
@@ -681,8 +681,11 @@ int main(int argc, char** argv)
     //
     // Set global config variables
     //
-    if (cfg.chunk_size != SRT_LIVE_MAX_PLSIZE)
+    if (cfg.chunk_size != 0)
         transmit_chunk_size = cfg.chunk_size;
+    else
+        transmit_chunk_size = SRT_MAX_PLSIZE_AF_INET;
+
     transmit_stats_writer = SrtStatsWriterFactory(cfg.stats_pf);
     transmit_bw_report = cfg.bw_report;
     transmit_stats_report = cfg.stats_report;

apps/transmitmedia.cpp

@@ -44,7 +44,7 @@ bool g_stats_are_printed_to_stdout = false;
 bool transmit_total_stats = false;
 unsigned long transmit_bw_report = 0;
 unsigned long transmit_stats_report = 0;
-unsigned long transmit_chunk_size = SRT_LIVE_MAX_PLSIZE;
+unsigned long transmit_chunk_size = SRT_MAX_PLSIZE_AF_INET6;
 
 class FileSource: public Source
 {
@@ -179,6 +179,40 @@ void SrtCommon::InitParameters(string host, map<string,string> par)
         m_adapter = host;
     }
 
+    unsigned int max_payload_size = 0;
+
+    // Try to interpret host and adapter first
+    sockaddr_any host_sa, adapter_sa;
+
+    if (host != "")
+    {
+        host_sa = CreateAddr(host);
+        if (host_sa.family() == AF_UNSPEC)
+            Error("Failed to interpret 'host' spec: " + host);
+
+        if (host_sa.family() == AF_INET)
+            max_payload_size = SRT_MAX_PLSIZE_AF_INET;
+    }
+
+    if (adapter != "" && adapter != host)
+    {
+        adapter_sa = CreateAddr(adapter);
+
+        if (adapter_sa.family() == AF_UNSPEC)
+            Error("Failed to interpret 'adapter' spec: " + adapter);
+
+        if (host_sa.family() != AF_UNSPEC && host_sa.family() != adapter_sa.family())
+        {
+            Error("Both host and adapter specified and they use different IP versions");
+        }
+
+        if (max_payload_size == 0 && host_sa.family() == AF_INET)
+            max_payload_size = SRT_MAX_PLSIZE_AF_INET;
+    }
+
+    if (!max_payload_size)
+        max_payload_size = SRT_MAX_PLSIZE_AF_INET6;
+
     if (par.count("tsbpd") && false_names.count(par.at("tsbpd")))
     {
         m_tsbpdmode = false;
@@ -195,11 +229,17 @@ void SrtCommon::InitParameters(string host, map<string,string> par)
     if ((par.count("transtype") == 0 || par["transtype"] != "file")
         && transmit_chunk_size > SRT_LIVE_DEF_PLSIZE)
     {
-        if (transmit_chunk_size > SRT_LIVE_MAX_PLSIZE)
-            throw std::runtime_error("Chunk size in live mode exceeds 1456 bytes; this is not supported");
+        if (transmit_chunk_size > max_payload_size)
+            Error(Sprint("Chunk size in live mode exceeds ", max_payload_size, " bytes; this is not supported"));
 
         par["payloadsize"] = Sprint(transmit_chunk_size);
     }
+    else
+    {
+        // set it so without making sure that it was set to "file".
+        // worst case it will be rejected in settings
+        m_transtype = SRTT_FILE;
+    }
 
     // Assign the others here.
     m_options = par;
@@ -263,6 +303,21 @@ bool SrtCommon::AcceptNewClient()
         Error("srt_accept");
     }
 
+    int maxsize = srt_getmaxpayloadsize(m_sock);
+    if (maxsize == SRT_ERROR)
+    {
+        srt_close(m_bindsock);
+        srt_close(m_sock);
+        Error("srt_getmaxpayloadsize");
+    }
+
+    if (m_transtype == SRTT_LIVE && transmit_chunk_size > size_t(maxsize))
+    {
+        srt_close(m_bindsock);
+        srt_close(m_sock);
+        Error(Sprint("accepted connection's payload size ", maxsize, " is too small for required ", transmit_chunk_size, " chunk size"));
+    }
+
     // we do one client connection at a time,
     // so close the listener.
     srt_close(m_bindsock);
@@ -431,6 +486,19 @@ void SrtCommon::ConnectClient(string host, int port)
         Error("srt_connect");
     }
 
+    int maxsize = srt_getmaxpayloadsize(m_sock);
+    if (maxsize == SRT_ERROR)
+    {
+        srt_close(m_sock);
+        Error("srt_getmaxpayloadsize");
+    }
+
+    if (m_transtype == SRTT_LIVE && transmit_chunk_size > size_t(maxsize))
+    {
+        srt_close(m_sock);
+        Error(Sprint("accepted connection's payload size ", maxsize, " is too small for required ", transmit_chunk_size, " chunk size"));
+    }
+
     stat = ConfigurePost(m_sock);
     if ( stat == SRT_ERROR )
         Error("ConfigurePost");

apps/transmitmedia.hpp

@@ -42,6 +42,7 @@ class SrtCommon
     string m_mode;
     string m_adapter;
     map<string, string> m_options; // All other options, as provided in the URI
+    SRT_TRANSTYPE m_transtype = SRTT_LIVE;
     SRTSOCKET m_sock = SRT_INVALID_SOCK;
     SRTSOCKET m_bindsock = SRT_INVALID_SOCK;
     bool IsUsable() { SRT_SOCKSTATUS st = srt_getsockstate(m_sock); return st > SRTS_INIT && st < SRTS_BROKEN; }

docs/API/API-functions.md

@@ -19,6 +19,7 @@
 | [srt_bind_acquire](#srt_bind_acquire)             | Acquires a given UDP socket instead of creating one                                                            |
 | [srt_getsockstate](#srt_getsockstate)             | Gets the current status of the socket                                                                          |
 | [srt_getsndbuffer](#srt_getsndbuffer)             | Retrieves information about the sender buffer                                                                  |
+| [srt_getmaxpayloadsize](#srt_getmaxpayloadsize)   | Retrieves the information about the maximum payload size in a single packet                                    |
 | [srt_close](#srt_close)                           | Closes the socket or group and frees all used resources                                                        |
 | <img width=290px height=1px/>                     | <img width=720px height=1px/>                                                                                  |
 
@@ -28,7 +29,7 @@
 |:------------------------------------------------- |:-------------------------------------------------------------------------------------------------------------- |
 | [srt_listen](#srt_listen)                         | Sets up the listening state on a socket                                                                        |
 | [srt_accept](#srt_accept)                         | Accepts a connection; creates/returns a new socket or group ID                                                 |
-| [srt_accept_bond](#srt_accept_bond)               | Accepts a connection pending on any sockets passed in the `listeners` array <br/> of `nlisteners` size               |
+| [srt_accept_bond](#srt_accept_bond)               | Accepts a connection pending on any sockets passed in the `listeners` array <br/> of `nlisteners` size         |
 | [srt_listen_callback](#srt_listen_callback)       | Installs/executes a callback hook on a socket created to handle the incoming connection <br/> on a listening socket  |
 | [srt_connect](#srt_connect)                       | Connects a socket or a group to a remote party with a specified address and port                               |
 | [srt_connect_bind](#srt_connect_bind)             | Same as [`srt_bind`](#srt_bind) then [`srt_connect`](#srt_connect) if called with socket [`u`](#u)             |
@@ -166,13 +167,14 @@ Since SRT v1.5.0.
 | [SRT_REJ_VERSION](#SRT_REJ_VERSION)          | 1.3.4     | A party did not satisfy the minimum version requirement that had been set up for a connection                  |
 | [SRT_REJ_RDVCOOKIE](#SRT_REJ_RDVCOOKIE)      | 1.3.4     | Rendezvous cookie collision                                                                                    |
 | [SRT_REJ_BADSECRET](#SRT_REJ_BADSECRET)      | 1.3.4     | Both parties have defined a passphrase for connection and they differ                                          |
-| [SRT_REJ_UNSECURE](#SRT_REJ_UNSECURE)        | 1.3.4     | Only one connection party has set up a password                                                                |
+| [SRT_REJ_UNSECURE](#SRT_REJ_UNSECURE)        | 1.3.4     | Only one connection party has set up a password                                                                  |
 | [SRT_REJ_MESSAGEAPI](#SRT_REJ_MESSAGEAPI)    | 1.3.4     | The value for [`SRTO_MESSAGEAPI`](API-socket-options.md#SRTO_MESSAGEAPI) flag is different on both connection parties  |
 | [SRT_REJ_FILTER](#SRT_REJ_FILTER)            | 1.3.4     | The [`SRTO_PACKETFILTER`](API-socket-options.md#SRTO_PACKETFILTER) option has been set differently on both connection parties  |
-| [SRT_REJ_GROUP](#SRT_REJ_GROUP)              | 1.4.2     | The group type or some group settings are incompatible for both connection parties                             |
-| [SRT_REJ_TIMEOUT](#SRT_REJ_TIMEOUT)          | 1.4.2     | The connection wasn't rejected, but it timed out                                                               |
-| [SRT_REJ_CRYPTO](#SRT_REJ_CRYPTO)            | 1.5.2     | The connection was rejected due to an unsupported or mismatching encryption mode                               |
-| <img width=290px height=1px/>                |           |                                                                                                                |
+| [SRT_REJ_GROUP](#SRT_REJ_GROUP)              | 1.4.2     | The group type or some group settings are incompatible for both connection parties                               |
+| [SRT_REJ_TIMEOUT](#SRT_REJ_TIMEOUT)          | 1.4.2     | The connection wasn't rejected, but it timed out                                                                 |
+| [SRT_REJ_CRYPTO](#SRT_REJ_CRYPTO)            | 1.5.2     | The connection was rejected due to an unsupported or mismatching encryption mode                                 |
+| [SRT_REJ_CONFIG](#SRT_REJ_CONFIG)            | 1.6.0     | The connection was rejected because settings on both parties are in collision and cannot negotiate common values |
+| <img width=290px height=1px/>                |           |                                                                                                                  |
 
 See the full list in [Rejection Reason Codes](./rejection-codes.md).
 
@@ -294,6 +296,7 @@ This means that if you call [`srt_startup`](#srt_startup) multiple times, you ne
 * [srt_bind_acquire](#srt_bind_acquire)
 * [srt_getsockstate](#srt_getsockstate)
 * [srt_getsndbuffer](#srt_getsndbuffer)
+* [srt_getmaxpayloadsize](#srt_getmaxpayloadsize)
 * [srt_close](#srt_close)
 
 
@@ -541,6 +544,58 @@ This function can be used for diagnostics. It is especially useful when the
 socket needs to be closed asynchronously.
 
 
+[:arrow_up: &nbsp; Back to List of Functions & Structures](#srt-api-functions)
+
+---
+
+### srt_getmaxpayloadsize
+
+```
+int srt_getmaxpayloadsize(SRTSOCKET u);
+```
+
+Returns the maximum number of bytes that fit in a single packet. Useful only in
+live mode (when `SRTO_TSBPDMODE` is true). The socket must be bound (see
+[srt_bind](#srt_bind)) or connected (see [srt_connect](#srt_connect))
+to use this function. Note that in case when the socket is bound to an IPv6
+wildcard address and it is dual-stack (`SRTO_IPV6ONLY` is set to false), this
+function returns the correct value only if the socket is connected, otherwise
+it will return the value always as if the connection was made from an IPv6 peer
+(including when you call it on a listening socket).
+
+This function is only useful for the application to check if it is able to use
+a payload of certain size in the live mode, or after connection, if the application
+can send payloads of certain size. This is useful only in assertions, as if the
+[`SRTO_PAYLOADSIZE`](API_socket-options.md#SRTO_PAYLOADSIZE) option is to be
+set to a non-default value (for which the one returned by this function is the
+maximum value), this option should be modified before connection and on both
+parties, regarding the settings applied on the socket.
+
+The returned value is the maximum number of bytes that can be put in a single
+packet regarding:
+
+* The current MTU size (`SRTO_MSS`)
+* The IP version (IPv4 or IPv6)
+* The `SRTO_CRYPTOMODE` setting (bytes reserved for AEAD authentication tag)
+* The `SRTO_PACKETFILTER` setting (bytes reserved for extra field in a FEC control packet)
+
+With default options this value should be 1456 for IPv4 and 1444 for IPv6.
+
+
+|      Returns                  |                                                   |
+|:----------------------------- |:------------------------------------------------- |
+| The maximum payload size (>0) | If succeeded                                      |
+| `SRT_ERROR`                   | Usage error                                       |
+| <img width=240px height=1px/> | <img width=710px height=1px/>                     |
+
+|       Errors                            |                                                 |
+|:--------------------------------------- |:----------------------------------------------- |
+| [`SRT_EINVSOCK`](#srt_einvsock)         | Socket [`u`](#u) indicates no valid socket ID   |
+| [`SRT_EUNBOUNDSOCK`](#srt_eunboundsock) | Socket [`u`](#u) is not bound                   |
+| <img width=240px height=1px/>           | <img width=710px height=1px/>                   |
+
+
+
 [:arrow_up: &nbsp; Back to List of Functions & Structures](#srt-api-functions)
 
 ---
@@ -3071,6 +3126,21 @@ and above is reserved for "predefined codes" (`SRT_REJC_PREDEFINED` value plus
 adopted HTTP codes). Values above `SRT_REJC_USERDEFINED` are freely defined by
 the application.
 
+#### SRT_REJ_CRYPTO
+
+Settings for `SRTO_CRYPTOMODE` on both parties are not compatible with one another.
+See [`SRTO_CRYPTOMODE`](API-socket-options.md#SRTO_CRYPTOMODE) for details.
+
+#### SRT_REJ_CONFIG
+
+Settings for various transmission parameters that are supposed to be negotiated
+during the handshake (in order to agree upon a common value) are under restrictions
+that make finding common values for them impossible. Cases include:
+
+* `SRTO_PAYLOADSIZE`, which is nonzero in live mode, is set to a value that
+exceeds the free space in a single packet that results from the value of the
+negotiated MSS value
+
 
 [:arrow_up: &nbsp; Back to List of Functions & Structures](#srt-api-functions)