net: Add Tor extended SOCKS5 error codes

Add support for reporting Tor extended SOCKS5 error codes as defined
here:

- https://spec.torproject.org/socks-extensions.html#extended-error-codes
- https://gitlab.torproject.org/tpo/core/arti/-/blob/main/crates/tor-socksproto/src/msg.rs?ref_type=heads#L183

These give a more direct indication of the problem in case of errors
connecting to hidden services, for example:
```
2025-04-02T10:34:13Z [net] Socks5() connect to [elided].onion:8333 failed: onion service descriptor can not be found
```

In the C Tor implementation, to get these one should set the
"ExtendedErrors" flag on the "SocksPort" definition, introduced in
version 0.4.3.1.

In Arti, extended error codes are always enabled.

Also, report the raw error code in case of unknown reply values.

Author: laanwj

src/netbase.cpp

@@ -266,17 +266,25 @@ enum SOCKS5Command: uint8_t {
     UDP_ASSOCIATE = 0x03
 };
 
-/** Values defined for REP in RFC1928 */
+/** Values defined for REP in RFC1928 and https://spec.torproject.org/socks-extensions.html */
 enum SOCKS5Reply: uint8_t {
-    SUCCEEDED = 0x00,        //!< Succeeded
-    GENFAILURE = 0x01,       //!< General failure
-    NOTALLOWED = 0x02,       //!< Connection not allowed by ruleset
-    NETUNREACHABLE = 0x03,   //!< Network unreachable
-    HOSTUNREACHABLE = 0x04,  //!< Network unreachable
-    CONNREFUSED = 0x05,      //!< Connection refused
-    TTLEXPIRED = 0x06,       //!< TTL expired
-    CMDUNSUPPORTED = 0x07,   //!< Command not supported
-    ATYPEUNSUPPORTED = 0x08, //!< Address type not supported
+    SUCCEEDED = 0x00,                  //!< RFC1928: Succeeded
+    GENFAILURE = 0x01,                 //!< RFC1928: General failure
+    NOTALLOWED = 0x02,                 //!< RFC1928: Connection not allowed by ruleset
+    NETUNREACHABLE = 0x03,             //!< RFC1928: Network unreachable
+    HOSTUNREACHABLE = 0x04,            //!< RFC1928: Network unreachable
+    CONNREFUSED = 0x05,                //!< RFC1928: Connection refused
+    TTLEXPIRED = 0x06,                 //!< RFC1928: TTL expired
+    CMDUNSUPPORTED = 0x07,             //!< RFC1928: Command not supported
+    ATYPEUNSUPPORTED = 0x08,           //!< RFC1928: Address type not supported
+    TOR_HS_DESC_NOT_FOUND = 0xf0,      //!< Tor: Onion service descriptor can not be found
+    TOR_HS_DESC_INVALID = 0xf1,        //!< Tor: Onion service descriptor is invalid
+    TOR_HS_INTRO_FAILED = 0xf2,        //!< Tor: Onion service introduction failed
+    TOR_HS_REND_FAILED = 0xf3,         //!< Tor: Onion service rendezvous failed
+    TOR_HS_MISSING_CLIENT_AUTH = 0xf4, //!< Tor: Onion service missing client authorization
+    TOR_HS_WRONG_CLIENT_AUTH = 0xf5,   //!< Tor: Onion service wrong client authorization
+    TOR_HS_BAD_ADDRESS = 0xf6,         //!< Tor: Onion service invalid address
+    TOR_HS_INTRO_TIMEOUT = 0xf7,       //!< Tor: Onion service introduction timed out
 };
 
 /** Values defined for ATYPE in RFC1928 */
@@ -364,8 +372,24 @@ static std::string Socks5ErrorString(uint8_t err)
             return "protocol error";
         case SOCKS5Reply::ATYPEUNSUPPORTED:
             return "address type not supported";
+        case SOCKS5Reply::TOR_HS_DESC_NOT_FOUND:
+            return "onion service descriptor can not be found";
+        case SOCKS5Reply::TOR_HS_DESC_INVALID:
+            return "onion service descriptor is invalid";
+        case SOCKS5Reply::TOR_HS_INTRO_FAILED:
+            return "onion service introduction failed";
+        case SOCKS5Reply::TOR_HS_REND_FAILED:
+            return "onion service rendezvous failed";
+        case SOCKS5Reply::TOR_HS_MISSING_CLIENT_AUTH:
+            return "onion service missing client authorization";
+        case SOCKS5Reply::TOR_HS_WRONG_CLIENT_AUTH:
+            return "onion service wrong client authorization";
+        case SOCKS5Reply::TOR_HS_BAD_ADDRESS:
+            return "onion service invalid address";
+        case SOCKS5Reply::TOR_HS_INTRO_TIMEOUT:
+            return "onion service introduction timed out";
         default:
-            return "unknown";
+            return strprintf("unknown (0x%02x)", err);
     }
 }