fix utp flags leaking into the actual socket transmission

clang-format

llarp/ev.cpp

@@ -124,13 +124,13 @@ llarp_ev_udp_sendto(struct llarp_udp_io *udp, const sockaddr *to,
     errno = 0;
   }
 #else
-  char ebuf[1024];
-  int err = WSAGetLastError();
-  FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, nullptr, err, LANG_NEUTRAL, ebuf,
-                1024, nullptr);
-  llarp::LogWarn("sendto failed: ", buf, ":", err);
+    char ebuf[1024];
+    int err = WSAGetLastError();
+    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, nullptr, err, LANG_NEUTRAL, ebuf,
+                  1024, nullptr);
+    llarp::LogWarn("sendto failed: ", buf);
     WSASetLastError(0);
-	}
+  }
 #endif
   return ret;
 }

llarp/ev.hpp

@@ -644,7 +644,7 @@ namespace llarp
 struct llarp_ev_loop
 {
   byte_t readbuf[EV_READ_BUF_SZ] = {0};
-  llarp_time_t _now = 0;
+  llarp_time_t _now              = 0;
   virtual bool
   init() = 0;
   virtual int

llarp/handlers/exit.cpp

@@ -261,7 +261,7 @@ namespace llarp
         std::string nmask_str = v.substr(1 + pos);
         std::string host_str  = v.substr(0, pos);
         // string, or just a plain char array?
-        strncpy(m_Tun.ifaddr, host_str.c_str(), sizeof(m_Tun.ifaddr)-1);
+        strncpy(m_Tun.ifaddr, host_str.c_str(), sizeof(m_Tun.ifaddr) - 1);
         m_Tun.netmask = std::atoi(nmask_str.c_str());
 
         llarp::Addr ifaddr(host_str);
@@ -273,7 +273,7 @@ namespace llarp
       }
       if(k == "ifname")
       {
-        strncpy(m_Tun.ifname, v.c_str(), sizeof(m_Tun.ifname)-1);
+        strncpy(m_Tun.ifname, v.c_str(), sizeof(m_Tun.ifname) - 1);
         llarp::LogInfo(Name(), " set ifname to ", m_Tun.ifname);
       }
       if(k == "exit-whitelist")

llarp/link/utp.cpp

@@ -20,6 +20,10 @@
 #include <wspiapi.h>
 #endif
 
+#ifndef IP_DONTFRAGMENT
+#define IP_DONTFRAGMENT IP_DONTFRAG
+#endif
+
 namespace llarp
 {
   namespace utp
@@ -330,13 +334,59 @@ namespace llarp
             static_cast< LinkLayer* >(utp_context_get_userdata(arg->context));
         llarp::LogDebug("utp_sendto ", Addr(*arg->address), " ", arg->len,
                         " bytes");
+        // For whatever reason, the UTP_UDP_DONTFRAG flag is set
+        // on the socket itself....which isn't correct and causes
+        // winsock (at minimum) to reeee
+        // here, we check its value, then set fragmentation the _right_
+        // way. Naturally, Linux has its own special procedure.
+        // Of course, the flag itself is cleared. -rick
 #ifndef _WIN32
+#ifndef __linux__
+        if(arg->flags == 2)
+        {
+          int val = 1;
+          setsockopt(l->m_udp.fd, IPPROTO_IP, IP_DONTFRAGMENT, &val,
+                     sizeof(val));
+        }
+        else
+        {
+          int val = 0;
+          setsockopt(l->m_udp.fd, IPPROTO_IP, IP_DONTFRAGMENT, &val,
+                     sizeof(val));
+        }
+#else
+        if(arg->flags == 2)
+        {
+          int val = IP_PMTUDISC_DO;
+          setsockopt(l->m_udp.fd, IPPROTO_IP, IP_MTU_DISCOVER, &val,
+                     sizeof(val));
+        }
+        else
+        {
+          int val = IP_PMTUDISC_DONT;
+          setsockopt(l->m_udp.fd, IPPROTO_IP, IP_MTU_DISCOVER, &val,
+                     sizeof(val));
+        }
+#endif
+        arg->flags = 0;
         if(::sendto(l->m_udp.fd, (char*)arg->buf, arg->len, arg->flags,
                     arg->address, arg->address_len)
                == -1
            && errno)
 #else
-        WSASetLastError(0);
+        if(arg->flags == 2)
+        {
+          char val = 1;
+          setsockopt(l->m_udp.fd, IPPROTO_IP, IP_DONTFRAGMENT, &val,
+                     sizeof(val));
+        }
+        else
+        {
+          char val = 0;
+          setsockopt(l->m_udp.fd, IPPROTO_IP, IP_DONTFRAGMENT, &val,
+                     sizeof(val));
+        }
+        arg->flags = 0;
         if(::sendto(l->m_udp.fd, (char*)arg->buf, arg->len, arg->flags,
                     arg->address, arg->address_len)
            == -1)
@@ -347,7 +397,6 @@ namespace llarp
           FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, nullptr, err, LANG_NEUTRAL,
                         buf, 1024, nullptr);
           llarp::LogError("sendto failed: ", buf);
-          llarp::LogInfo("flags: ", arg->flags);
         }
         return 0;
       }