httpd: if no request was given at all, close the socket without generating error page

For one, an attacker can try to overload us by just opening and immediately
closing tons of connections - reduce our work to the minimum for this case.

function                                             old     new   delta
handle_incoming_and_exit                            2172    2200     +28
.rodata                                           103225  103246     +21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 49/0)               Total: 49 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 30 insertions, 21 deletions

diff --git a/networking/httpd.c b/networking/httpd.c
index 6bc58995b..fb6ffe542 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -305,6 +305,12 @@
 
 #define DEBUG 0
 
+#if DEBUG
+# define dbg(...) fprintf(stderr, __VA_ARGS__)
+#else
+# define dbg(...) ((void)0)
+#endif
+
 #define IOBUF_SIZE 8192
 #define MAX_HTTP_HEADERS_SIZE (32*1024)
 
@@ -1158,8 +1164,7 @@ static void send_headers(unsigned responseNum)
                         fprintf(stderr, "headers: '%s'\n", iobuf);
                 }
                 full_write(STDOUT_FILENO, iobuf, len);
-                if (DEBUG)
-                        fprintf(stderr, "writing error page: '%s'\n", error_page);
+                dbg("writing error page: '%s'\n", error_page);
                 return send_file_and_exit(error_page, SEND_BODY);
         }
 #endif
@@ -1500,8 +1505,7 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr, int post
                         }
                         if (full_write(STDOUT_FILENO, rbuf, count) != count)
                                 break;
-                        if (DEBUG)
-                                fprintf(stderr, "cgi read %d bytes: '%.*s'\n", count, count, rbuf);
+                        dbg("cgi read %d bytes: '%.*s'\n", count, count, rbuf);
                 } /* if (pfd[FROM_CGI].revents) */
         } /* while (1) */
         log_and_exit();
@@ -1747,8 +1751,7 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
                 /* file_size and last_mod are already populated */
         }
         if (fd < 0) {
-                if (DEBUG)
-                        bb_perror_msg("can't open '%s'", url);
+                dbg("can't open '%s'\n", url);
                 /* Error pages are sent by using send_file_and_exit(SEND_BODY).
                  * IOW: it is unsafe to call send_headers_and_exit
                  * if what is SEND_BODY! Can recurse! */
@@ -1761,8 +1764,7 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
         sprintf(G.etag, "\"%llx-%llx\"", (unsigned long long)last_mod, (unsigned long long)file_size);
 
         if (G.if_none_match) {
-                if (DEBUG)
-                        bb_perror_msg("If-None-Match and file's ETag are: '%s' '%s'\n", G.if_none_match, G.etag);
+                dbg("If-None-Match:'%s' file's ETag:'%s'\n", G.if_none_match, G.etag);
                 /* Weak ETag comparision.
                  * If-None-Match may have many ETags but they are quoted so we can use simple substring search */
                 if (strstr(G.if_none_match, G.etag))
@@ -1838,9 +1840,7 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
                 }
         }
 
-        if (DEBUG)
-                bb_error_msg("sending file '%s' content-type: %s",
-                        url, found_mime_type);
+        dbg("sending file '%s' content-type:%s\n", url, found_mime_type);
 
 #if ENABLE_FEATURE_HTTPD_RANGES
         if (what == SEND_BODY /* err pages and ranges don't mix */
@@ -1910,9 +1910,7 @@ static void if_ip_denied_send_HTTP_FORBIDDEN_and_exit(unsigned remote_ip)
         Htaccess_IP *cur;
 
         for (cur = G.ip_a_d; cur; cur = cur->next) {
-#if DEBUG
-                fprintf(stderr,
-                        "checkPermIP: '%s' ? '%u.%u.%u.%u/%u.%u.%u.%u'\n",
+                dbg("checkPermIP: '%s' ? '%u.%u.%u.%u/%u.%u.%u.%u'\n",
                         rmt_ip_str,
                         (unsigned char)(cur->ip >> 24),
                         (unsigned char)(cur->ip >> 16),
@@ -1923,7 +1921,6 @@ static void if_ip_denied_send_HTTP_FORBIDDEN_and_exit(unsigned remote_ip)
                         (unsigned char)(cur->mask >> 8),
                         (unsigned char)(cur->mask)
                 );
-#endif
                 if ((remote_ip & cur->mask) == cur->ip) {
                         if (cur->allow_deny == 'A')
                                 return;
@@ -2015,8 +2012,7 @@ static int check_user_passwd(const char *path, char *user_and_passwd)
                 if (prev && strcmp(prev, dir_prefix) != 0)
                         continue;
 
-                if (DEBUG)
-                        fprintf(stderr, "checkPerm: '%s' ? '%s'\n", dir_prefix, user_and_passwd);
+                dbg("checkPerm: '%s' ? '%s'\n", dir_prefix, user_and_passwd);
 
                 /* If it's not a prefix match, continue searching */
                 len = strlen(dir_prefix);
@@ -2231,8 +2227,22 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
         /* Install timeout handler. get_line() needs it. */
         signal(SIGALRM, send_REQUEST_TIMEOUT_and_exit);
 
-        if (!get_line()) /* EOF or error or empty line */
-                send_headers_and_exit(HTTP_BAD_REQUEST);
+        if (!get_line()) { /* EOF or error or empty line */
+                /* Observed Firefox to "speculatively" open
+                 * extra connections to a new site on first access,
+                 * they are closed in ~5 seconds with nothing
+                 * being sent at all.
+                 * (Presumably it's a method to decrease latency?)
+                 */
+                if (verbose > 2)
+                        bb_simple_error_msg("eof on read, closing");
+                /* Don't bother generating error page in this case,
+                 * just close the socket.
+                 */
+                //send_headers_and_exit(HTTP_BAD_REQUEST);
+                _exit(xfunc_error_retval);
+        }
+        dbg("Request:'%s'\n", iobuf);
 
         /* Find URL */
         // rfc2616: method and URI is separated by exactly one space
@@ -2445,8 +2455,7 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
                 if (total_headers_len >= MAX_HTTP_HEADERS_SIZE)
                         send_headers_and_exit(HTTP_ENTITY_TOO_LARGE);
 #endif
-                if (DEBUG)
-                        bb_error_msg("header: '%s'", iobuf);
+                dbg("header:'%s'\n", iobuf);
 #if ENABLE_FEATURE_HTTPD_CGI
                 /* Only POST needs to know POST_length */
                 if (prequest == request_POST && STRNCASECMP(iobuf, "Content-Length:") == 0) {