yhttpd: port ychat fixes, get it building + stable in Docker (task 9s0)

Ports the ychat revival fixes (unsigned/size_t npos truncation, ofstream
== NULL, tool::trim OOB, CGI popen -> execve, www.yChat.org links, g++
version gate, config.pl -I., NCURSES/CLI-disabled build) so yhttpd builds
on modern GCC in a Rocky Linux 9 container, plus yhttpd-specific fixes
found while verifying it under concurrent load:

- listen() backlog was hardcoded to 1; bumped to SOMAXCONN.
- sock::_close() closed sockets with unread request bytes still in the
  kernel receive buffer (read_http() only reads the GET line), so Linux
  sent an abortive RST instead of a FIN, racing the client's read of the
  response ("connection reset by peer" even though it was delivered).
  Fixed with a non-blocking, bounded drain before close() - confirmed via
  tcpdump: RSTs on every response before, zero after, across 140+
  requests / concurrent bursts of 20.
- Removed a duplicate _make_server_socket() call in start() (wrap.cpp's
  init_wrapper() already makes it before start() runs) that leaked a fd
  and would have double-initialized SSL if OPENSSL is ever enabled;
  caught by fresh-context review, documented honestly in DOCKER.md.
- src/configure's dependency-checker predates 64-bit multilib distros
  (only checked /usr/lib, never /usr/lib64) and was missing an ncur
  move-aside entry for the NCURSES-disabled build.

Added Dockerfile/.dockerignore/DOCKER.md documenting the build, the fixes,
and the one known-but-unfixed landmine (a SIGILL heap corruption in
sock::_close that reproduces on newer host GCC/glibc but not in the
container - latent, not fixed).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/yhttpd/src/reqp.cpp b/yhttpd/src/reqp.cpp
index df9de5d..4ce30d9 100644
--- a/yhttpd/src/reqp.cpp
+++ b/yhttpd/src/reqp.cpp
@@ -22,7 +22,7 @@ void
 reqp::get_request_parameters( string s_parameters, map<string,string>& map_params )
 {
   string s_tmp;
-  unsigned i_pos, i_pos2;
+  size_t i_pos, i_pos2;
 
   while( (i_pos = s_parameters.find("&")) != string::npos )
   {
@@ -46,7 +46,7 @@ reqp::get_request_parameters( string s_parameters, map<string,string>& map_param
 string
 reqp::get_url( string s_req, map<string, string> &map_params, int& i_postpayloadoffset )
 {
-  unsigned i_pos, i_pos2;
+  size_t i_pos, i_pos2;
   string s_vars( "" );
   string s_ret;
   int i_req;
@@ -111,7 +111,6 @@ reqp::get_url( string s_req, map<string, string> &map_params, int& i_postpayload
 
   if ( s_ret.empty() )
     s_ret = wrap::CONF->get_elem( "httpd.startsite" );
-
   else
     s_ret = remove_dots(s_ret);
 
@@ -211,7 +210,7 @@ reqp::url_decode( string s_url )
 string
 reqp::get_from_header( string s_req, string s_hdr )
 {
-  unsigned i_pos[2];
+  size_t i_pos[2];
   if ( (i_pos[0] = s_req.find( s_hdr, 0 )) == string::npos )
     return "";
 
@@ -274,7 +273,7 @@ string
 reqp::remove_dots( string s_ret )
 {
   // remove ".." from the request.
-  unsigned i_pos;
+  size_t i_pos;
 
   if ( (i_pos = s_ret.find( ".." )) != string::npos )
     return remove_dots(s_ret.substr(0, i_pos));