Replace libowfat's event waiter with our own abstraction

It's with a heavy heart that I remove libowfat as my event library from
opentracker.

libowfat is what taught opentracker to walk and then fly. The tracker was
literally standing on the shoulder of giants when I started writing it in
2006. For its time, the event abstraction was unparalleled and it has
held up for many years, and it served the bittorrent community greatly.

https://erdgeist.org/gitweb/opentracker/commit/?id=ad472597c569568bad0526d116b601dfcb36638c

Unfortunately, it is very likely that libowfat will not be maintained
anymore for the foreseeable future, it is already not easy to get its
source from upstream and opentracker started receiving bug reports that I
can not reasonably answer or patch.

Before the project gets more dependent on the limitations of libowfat's
current state, I need to teach opentracker to stand on its own feet and
fly by itself. I've learned a great deal in the process and have even
more respect now for what libowfat pioneered.

The path for opentracker is cleared now. Ground work has already been
laid in the migration process to support multi threaded http processing
while keeping the aggressive reduction of syscalls alive that made the
libowfat+opentracker combo so scalable.

Here be some dragons, though: Even though there is a unit test suite
now, the event loop's rewrite has not been battle tested yet. So you
might want to hold up for a bit before jumping on the solo band wagon.

What awaits at the end will be a long overdue v1.0, which will be named
in honour of Felix.

1 files changed, 26 insertions, 13 deletions

diff --git a/ot_http.c b/ot_http.c
index 3c135cb..5e10d59 100644
--- a/ot_http.c
+++ b/ot_http.c
@@ -14,9 +14,6 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-/* Libowfat */
-#include "io.h"
-
 /* Opentracker */
 #include "ot_accesslist.h"
 #include "ot_fullscrape.h"
@@ -25,6 +22,7 @@
 #include "ot_ip.h"
 #include "ot_mutex.h"
 #include "ot_scan.h"
+#include "ot_event.h"
 #include "ot_fdstate.h"
 #include "ot_stats.h"
 #include "ot_urlencoded.h"
@@ -43,7 +41,7 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
   ssize_t           written_size;
 
   if (!cookie) {
-    io_close(sock);
+    event_del((int)sock), close((int)sock);
     return;
   }
 
@@ -67,7 +65,7 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
   if ((written_size < 0) || ((written_size == ws->reply_size) && !ws->keep_alive)) {
     buf_reset(&cookie->request);
     free(cookie);
-    io_close(sock);
+    event_del((int)sock), close((int)sock);
     return;
   }
 
@@ -77,7 +75,7 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
     if (!(outbuf = malloc(ws->reply_size - written_size))) {
       buf_reset(&cookie->request);
       free(cookie);
-      io_close(sock);
+      event_del((int)sock), close((int)sock);
       return;
     }
 
@@ -88,7 +86,7 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
         free(outbuf);
         buf_reset(&cookie->request);
         free(cookie);
-        io_close(sock);
+        event_del((int)sock), close((int)sock);
         return;
       }
     }
@@ -98,9 +96,9 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
     /* writeable short data sockets just have a tcp timeout */
     if (!ws->keep_alive) {
       fdstate_set_expiry(sock, 0);
-      io_dontwantread(sock);
+      http_interest_drop(sock, cookie, EVENT_IN);
     }
-    io_wantwrite(sock);
+    http_interest_add(sock, cookie, EVENT_OUT);
   }
 }
 
@@ -113,6 +111,21 @@ static void http_senddata(const int64_t sock, struct ot_workstruct *ws) {
 #define HTTPERROR_403_IP         return http_issue_error(sock, ws, CODE_HTTPERROR_403_IP)
 #define HTTPERROR_404            return http_issue_error(sock, ws, CODE_HTTPERROR_404)
 #define HTTPERROR_500            return http_issue_error(sock, ws, CODE_HTTPERROR_500)
+static void http_interest(const int64_t sock, struct http_data *cookie, int what) {
+  if (cookie->interest == what)
+    return;
+  cookie->interest = what;
+  event_modify((int)sock, what, fdstate_generation((int)sock));
+}
+
+void http_interest_add(const int64_t sock, struct http_data *cookie, int what) {
+  http_interest(sock, cookie, cookie->interest | what);
+}
+
+void http_interest_drop(const int64_t sock, struct http_data *cookie, int what) {
+  http_interest(sock, cookie, cookie->interest & ~what);
+}
+
 ssize_t http_issue_error(const int64_t sock, struct ot_workstruct *ws, int code) {
   const char *error_code[] = {"302 Found",      "400 Invalid Request", "400 Invalid Request", "400 Invalid Request",      "402 Payment Required",
                         "403 Not Modest", "403 Access Denied",   "404 Not Found",       "500 Internal Server Error"};
@@ -157,7 +170,7 @@ ssize_t http_sendiovecdata(const int64_t sock, struct ot_workstruct *ws, size_t
 
   /* If we came here, wait for the answer is over */
   if (cookie->flag & STRUCT_HTTP_FLAG_WAITINGFORTASK) {
-    io_dontwantread(sock);
+    http_interest_drop(sock, cookie, EVENT_IN);
     cookie->flag &= ~STRUCT_HTTP_FLAG_WAITINGFORTASK;
   }
 
@@ -208,7 +221,7 @@ ssize_t http_sendiovecdata(const int64_t sock, struct ot_workstruct *ws, size_t
   }
 
   fdstate_set_expiry(sock, g_now_seconds + OT_CLIENT_TIMEOUT_SEND);
-  io_wantwrite(sock);
+  http_interest_add(sock, cookie, EVENT_OUT);
   return 0;
 }
 
@@ -303,7 +316,7 @@ static ssize_t http_handle_stats(const int64_t sock, struct ot_workstruct *ws, c
     /* Clients waiting for us should not easily timeout */
     fdstate_set_expiry(sock, 0);
     fullscrape_deliver(sock, format);
-    io_dontwantread(sock);
+    http_interest_drop(sock, cookie, EVENT_IN);
     return ws->reply_size = -2;
   }
 #endif
@@ -396,7 +409,7 @@ static ssize_t http_handle_fullscrape(const int64_t sock, struct ot_workstruct *
   /* Clients waiting for us should not easily timeout */
   fdstate_set_expiry(sock, 0);
   fullscrape_deliver(sock, format);
-  io_dontwantread(sock);
+  http_interest_drop(sock, cookie, EVENT_IN);
   return ws->reply_size = -2;
 }
 #endif