From 9002d3350cc2086f95c8e850dee3e3ef9d8b11ac Mon Sep 17 00:00:00 2001
From: Viktor Szakats <commit@vsz.me>
Date: Sun, 14 Jun 2026 14:36:24 +0200
Subject: [PATCH] servers: minor socket error handling fixes

- sws: fix socket error code in `select()` failure message.
  Spotted by Copilot
  Bug: https://github.com/curl/curl/pull/21998#discussion_r3409469444
- sws: do not call `SOCKERRNO` twice on error.
- dnsd: do not call `SOCKERRNO` twice on error.
- dnsd: replace `goto` with `while()` to sync with rest of code.
- dnsd: `sendto()` fail message fixes:
  - replace `int` cast with `%zu` mask.
  - drop redundant newline.
  - show socket error string like rest of code.
  - report not-fully-sent error separately from socket errors.

Closes #22007
---
 tests/server/dnsd.c | 21 +++++++++++++--------
 tests/server/sws.c  |  8 +++++---
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/tests/server/dnsd.c b/tests/server/dnsd.c
index 443d93aa15..8fb899bf26 100644
--- a/tests/server/dnsd.c
+++ b/tests/server/dnsd.c
@@ -346,15 +346,20 @@ static struct resp *resp_queue;
 static CURLcode send_resp(curl_socket_t sock, struct resp *resp)
 {
   ssize_t rc;
+  int sockerr = 0;
 
-sending:
-  rc = sendto(sock, (const void *)resp->body.data, (SENDTO3)resp->body.dlen, 0,
-              &resp->addr, resp->addrlen);
-  if((rc < 0) && (SOCKERRNO == SOCKEINTR))
-    goto sending;
-  if(rc != (ssize_t)resp->body.dlen) {
-    logmsg("failed sending %d bytes, errno=%d\n",
-           (int)resp->body.dlen, SOCKERRNO);
+  do {
+    rc = sendto(sock, (const void *)resp->body.data, (SENDTO3)resp->body.dlen,
+                0, &resp->addr, resp->addrlen);
+  } while((rc < 0) && ((sockerr = SOCKERRNO) == SOCKEINTR));
+  if(rc < 0) {
+    char errbuf[STRERROR_LEN];
+    logmsg("failed sending %zu bytes, error: (%d) %s", resp->body.dlen,
+           sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
+    return CURLE_SEND_ERROR;
+  }
+  else if(rc != (ssize_t)resp->body.dlen) {
+    logmsg("failed sending %zu bytes, sent: %zd", resp->body.dlen, rc);
     return CURLE_SEND_ERROR;
   }
   logmsg("[%d] sent response", resp->qid);
diff --git a/tests/server/sws.c b/tests/server/sws.c
index 071d90846a..04d97560ef 100644
--- a/tests/server/sws.c
+++ b/tests/server/sws.c
@@ -1343,7 +1343,8 @@ static curl_socket_t connect_to(const char *ipaddr, unsigned short port)
       FD_SET(serverfd, &output);
       while(1) {
         rc = select((int)serverfd + 1, NULL, &output, NULL, &timeout);
-        if(rc < 0 && SOCKERRNO != SOCKEINTR)
+        sockerr = SOCKERRNO;
+        if(rc < 0 && sockerr != SOCKEINTR)
           goto error;
         else if(rc > 0) {
           curl_socklen_t errSize = sizeof(sockerr);
@@ -2328,15 +2329,16 @@ static int test_sws(int argc, const char *argv[])
     if(got_exit_signal)
       goto sws_cleanup;
 
+    sockerr = 0;
     do {
       rc = select((int)maxfd + 1, &input, &output, NULL, &timeout);
-    } while(rc < 0 && SOCKERRNO == SOCKEINTR && !got_exit_signal);
+    } while(rc < 0 && ((sockerr = SOCKERRNO) == SOCKEINTR &&
+            !got_exit_signal));
 
     if(got_exit_signal)
       goto sws_cleanup;
 
     if(rc < 0) {
-      sockerr = SOCKERRNO;
       logmsg("select() failed with error (%d) %s",
              sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
       goto sws_cleanup;