From 62e08d084c9a49effce5ac246e6e6f786d1a8b92 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Tue, 17 Dec 2024 12:12:35 -0500
Subject: [PATCH] Don't Error when sendto() errors with ENETUNREACH or
 EHOSTUNREACH

Don't latch for transient TX errors (eg. routing change
when NIC unplugged).

Eliminate SocketBusy since SOCK_EWOULDBLOCK is no longer
quite such a special case.
---
 src/driver/device.cpp | 22 +++++++++++++++++-----
 src/util/utils.cpp    |  4 ----
 src/util/utils.h      |  6 ------
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/driver/device.cpp b/src/driver/device.cpp
index 1289ea1..c851553 100644
--- a/src/driver/device.cpp
+++ b/src/driver/device.cpp
@@ -449,9 +449,17 @@ void Device::handle_send(Guard& G)
             // non-blocking sendto(), so we don't unlock here
             sock.sendto(peer_addr, (const char*)&msg.buf[0], msg.buf.size()*4);
             cnt_sent++;
-        }catch(SocketBusy&){
-            want_to_send = true;
-            return;
+        }catch(SocketError& e){
+            if(e.code==SOCK_EWOULDBLOCK) {
+                want_to_send = true;
+                return;
+            } else if(e.code==ENETUNREACH || e.code==EHOSTUNREACH) {
+                IFDBG(1, "Unable to send to %s : (%d) %s", peer_name.c_str(), e.code, e.what());
+                // Don't throw (and latch into Error state) what is probably
+                // a transient error.  Will timeout since packet wasn't sent
+            } else {
+                throw;
+            }
         }
         IFDBG(1, "Send seq=%08x %zu bytes", (unsigned)msg.seq, msg.buf.size()*4u);
 
@@ -952,8 +960,12 @@ void Device::run()
                                 doProcess[i] = true;
                                 cnt_recv++;
                                 cnt_recv_bytes += unsigned(feedUDPHeaderSize) + bufs[i].size();
-                            }catch(SocketBusy&){
-                                break;
+                            }catch(SocketError& e){
+                                if(e.code==SOCK_EWOULDBLOCK) {
+                                    break;
+                                } else {
+                                    throw;
+                                }
                             }
 
                             if(!doProcess[i]) {
diff --git a/src/util/utils.cpp b/src/util/utils.cpp
index f3b1459..c3e5c47 100644
--- a/src/util/utils.cpp
+++ b/src/util/utils.cpp
@@ -106,8 +106,6 @@ void Socket::sendto(const osiSockAddr& dest, const char* buf, size_t buflen) con
     ssize_t ret = ::sendto(sock, buf, buflen, 0, &dest.sa, sizeof(dest));
     if(ret<0) {
         int code = SOCKERRNO;
-        if(code==SOCK_EWOULDBLOCK)
-            throw SocketBusy();
         throw SocketError(code);
     } else if(size_t(ret)!=buflen)
         throw std::runtime_error("Incomplete sendto()");
@@ -119,8 +117,6 @@ size_t Socket::recvfrom(osiSockAddr& src, char* buf, size_t buflen) const
     ssize_t ret = ::recvfrom(sock, buf, buflen, 0, &src.sa, &len);
     if(ret<0) {
         int code = SOCKERRNO;
-        if(code==SOCK_EWOULDBLOCK)
-            throw SocketBusy();
         throw SocketError(code);
     }
     return size_t(ret);
diff --git a/src/util/utils.h b/src/util/utils.h
index 5973b4d..e1a1beb 100644
--- a/src/util/utils.h
+++ b/src/util/utils.h
@@ -59,12 +59,6 @@ struct epicsShareClass SocketError : public std::exception
     const char *what() const throw();
 };
 
-struct epicsShareClass SocketBusy : public SocketError
-{
-    SocketBusy() :SocketError(SOCK_EWOULDBLOCK) {}
-    virtual ~SocketBusy() throw() {}
-};
-
 // RAII handle to ensure that sockets aren't leaked
 // and helper to make socket calls throw SocketError
 struct Socket