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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=18719 TCP_NOPUSH dependency causes requests to fail Summary: TCP_NOPUSH dependency causes requests to fail Product: Apache httpd-2.0 Version: 2.0.45 Platform: All OS/Version: Linux Status: NEW Severity: Major Priority: Other Component: Core AssignedTo: bugs@httpd.apache.org ReportedBy: [EMAIL PROTECTED] Below is a full train-of-debugging log of my research into this problem. At the end of this log is my conclusion, with recommendations and a workaround. I have not submitted a patch because there are multiple methods of correction, and the decision of which to implement may be debatable. --------------------------------------------------------------- Indications: - when requesting many static files, the server does not output any data. - many png and jpg icons fall prey to this, in addition to many html files and random data, though it seems the stock gif icons do not. I have not researched this further. - httpd aborts the connection with no output (not even headers). - informational messages in logs (log level INFO): [Tue Apr 01 11:34:43 2003] [info] (70023)This function has not been implemented on this platform: core_output_filter: writing data to the network Investigation: - core.c (4029): ap_log_error(). **** backtrace **** Breakpoint 1, 0x40176509 in apr_strerror () from /usr/pkg/apache/lib/libapr-0.so.0 (gdb) bt #0 0x40176509 in apr_strerror () from /usr/pkg/apache/lib/libapr-0.so.0 #1 0x808f65a in log_error_core (file=0x80be6ca "core.c", line=4029, level=6, status=70023, s=0x8152828, r=0x0, pool=0x0, fmt=0x80c0be0 "core_output_filter: writing data to the network", args=0xbfffec28) at log.c:519 #2 0x808f86c in ap_log_error (file=0x80be6ca "core.c", line=4029, level=6, status=70023, s=0x8152828, fmt=0x80c0be0 "core_output_filter: writing data to the network") at log.c:561 #3 0x80a5847 in core_output_filter (f=0x815a230, b=0x81665f0) at core.c:4029 #4 0x809ac57 in ap_pass_brigade (next=0x815a230, bb=0x815f9c0) at util_filter.c:540 #5 0x80730a2 in ap_http_header_filter (f=0x815ecc8, b=0x815f9c0) at http_protocol.c:1716 #6 0x809ac57 in ap_pass_brigade (next=0x815ecc8, bb=0x815f9c0) at util_filter.c:540 #7 0x809dd17 in ap_content_length_filter (f=0x815ecb0, b=0x815f9c0) at protocol.c:1299 #8 0x809ac57 in ap_pass_brigade (next=0x815ecb0, bb=0x815f9c0) at util_filter.c:540 #9 0x8074c7e in ap_byterange_filter (f=0x815ec98, bb=0x815f9c0) at http_protocol.c:2881 #10 0x809ac57 in ap_pass_brigade (next=0x815ec98, bb=0x815f9c0) at util_filter.c:540 ---Type <return> to continue, or q <return> to quit--- #11 0x80a422c in default_handler (r=0x815e058) at core.c:3384 #12 0x808b2c1 in ap_run_handler (r=0x815e058) at config.c:194 #13 0x808bb0e in ap_invoke_handler (r=0x815e058) at config.c:401 #14 0x8075adc in ap_process_request (r=0x815e058) at http_request.c:288 #15 0x806fb6f in ap_process_http_connection (c=0x8159ee0) at http_core.c:293 #16 0x8098151 in ap_run_process_connection (c=0x8159ee0) at connection.c:85 #17 0x8098540 in ap_process_connection (c=0x8159ee0, csd=0x8159e18) at connection.c:207 #18 0x8089a67 in child_main (child_num_arg=2) at prefork.c:696 #19 0x8089c09 in make_child (s=0x80d1f48, slot=2) at prefork.c:790 #20 0x8089c84 in startup_children (number_to_start=3) at prefork.c:808 #21 0x808a0b6 in ap_mpm_run (_pconf=0x80cf840, plog=0x8107920, s=0x80d1f48) at prefork.c:1024 #22 0x8091183 in main (argc=3, argv=0xbffff2c4) at main.c:651 #23 0x4021a543 in __libc_start_main () from /lib/libc.so.6 **** relevant code (core.c:4029) **** if (rv != APR_SUCCESS) { ap_log_error(APLOG_MARK, APLOG_INFO, rv, c->base_server, "core_output_filter: writing data to the network"); **** last definition of rv **** rv = sendfile_it_all(net, /* the network information */ fd, /* the file to send */ &hdtr, /* header and trailer iovecs */ foffset, /* offset in the file to begin sending from */ flen, /* length of file */ nbytes + flen, /* total length including headers */ &bytes_sent, /* how many bytes were sent */ flags); /* apr_sendfile flags */ *** debugging *** --- in core.c/sendfile_it_all() --- (gdb) print file_bytes_left $3 = 484 (gdb) step 2760 rv = apr_sendfile(c->client_socket, fd, hdtr, &file_offset, &tmplen, (gdb) step 2762 *bytes_sent += tmplen; (gdb) print rv $4 = 70023 -------------------- ./srclib/apr/include/apr_errno.h:#define APR_ENOTIMPL (APR_OS_START_STATUS + 23) ./srclib/apr/include/apr_errno.h:#define APR_OS_START_STATUS (APR_OS_START_ERROR + APR_OS_ERRSPACE_SIZE) ./srclib/apr/include/apr_errno.h:#define APR_OS_START_ERROR 20000 ./srclib/apr/include/apr_errno.h:#define APR_OS_ERRSPACE_SIZE 50000 APR_ENOTIMPL == 70023 --------------------- ... after stepping through debugging data ... ./srclib/apr/network_io/unix/sockopt.c/apr_socket_opt_set() returns APR_ENOTIMPL (gdb) step 157 one = 1; (gdb) 160 if (opt & APR_SO_KEEPALIVE) { (gdb) 172 if (opt & APR_SO_DEBUG) { (gdb) 180 if (opt & APR_SO_REUSEADDR) { (gdb) 188 if (opt & APR_SO_SNDBUF) { (gdb) 200 if (opt & APR_SO_NONBLOCK) { (gdb) 213 if (opt & APR_SO_LINGER) { (gdb) 228 if (opt & APR_SO_TIMEOUT) { (gdb) 232 if (opt & APR_TCP_NODELAY) { (gdb) 262 if (opt & APR_TCP_NOPUSH) { (gdb) 307 return APR_ENOTIMPL; (gdb) bt #0 apr_socket_opt_set (sock=0x815a338, opt=1024, on=1) at sockopt.c:307 #1 0x4017bbb9 in apr_socket_sendfile (sock=0x815a338, file=0x815fdb0, hdtr=0xbfffec3c, offset=0xbfffec1c, len=0xbfffec00, flags=0) at sendrecv.c:299 #2 0x4017c036 in apr_sendfile (sock=0x815a338, file=0x815fdb0, hdtr=0xbfffec3c, offset=0xbfffec1c, len=0xbfffec00, flags=1) at sendrecv.c:1052 #3 0x80a3658 in sendfile_it_all (c=0x815a728, fd=0x815fdb0, hdtr=0xbfffec3c, file_offset=0, file_bytes_left=484, total_bytes_left=737, bytes_sent=0xbfffec4c, flags=1) at core.c:2760 #4 0x80a5699 in core_output_filter (f=0x815a750, b=0x8166580) at core.c:3964 #5 0x809ac57 in ap_pass_brigade (next=0x815a750, bb=0x815fec8) at util_filter.c:540 #6 0x80730a2 in ap_http_header_filter (f=0x815f1d0, b=0x815fec8) at http_protocol.c:1716 #7 0x809ac57 in ap_pass_brigade (next=0x815f1d0, bb=0x815fec8) at util_filter.c:540 #8 0x809dd17 in ap_content_length_filter (f=0x815f1b8, b=0x815fec8) at protocol.c:1299 #9 0x809ac57 in ap_pass_brigade (next=0x815f1b8, bb=0x815fec8) at util_filter.c:540 #10 0x8074c7e in ap_byterange_filter (f=0x815f1a0, bb=0x815fec8) at http_protocol.c:2881 #11 0x809ac57 in ap_pass_brigade (next=0x815f1a0, bb=0x815fec8) at util_filter.c:540 #12 0x80a422c in default_handler (r=0x815e560) at core.c:3384 #13 0x808b2c1 in ap_run_handler (r=0x815e560) at config.c:194 #14 0x808bb0e in ap_invoke_handler (r=0x815e560) at config.c:401 #15 0x8075adc in ap_process_request (r=0x815e560) at http_request.c:288 #16 0x806fb6f in ap_process_http_connection (c=0x815a400) at http_core.c:293 #17 0x8098151 in ap_run_process_connection (c=0x815a400) at connection.c:85 #18 0x8098540 in ap_process_connection (c=0x815a400, csd=0x815a338) at connection.c:207 #19 0x8089a67 in child_main (child_num_arg=1) at prefork.c:696 #20 0x8089c09 in make_child (s=0x80d1f48, slot=1) at prefork.c:790 #21 0x8089c84 in startup_children (number_to_start=4) at prefork.c:808 #22 0x808a0b6 in ap_mpm_run (_pconf=0x80cf840, plog=0x8107920, s=0x80d1f48) at prefork.c:1024 #23 0x8091183 in main (argc=3, argv=0xbffff2c4) at main.c:651 #24 0x40227543 in __libc_start_main () from /lib/libc.so.6 --------------- APR_TCP_NOPUSH == 1024 APR_TCP_NODELAY == 512 APR_INCOMPLETE_READ == 4096 --------------- APR_TCP_NODELAY is set upon connection Problematic files set APR_TCP_NOPUSH and exit before output Acceptable files set APR_INCOMPLETE_READ after complete output *** acceptable files *** (gdb) bt #0 apr_socket_opt_set (sock=0x815a338, opt=4096, on=1) at sockopt.c:156 #1 0x8098474 in ap_lingering_close (c=0x815a400) at connection.c:183 #2 0x8089a76 in child_main (child_num_arg=1) at prefork.c:697 #3 0x8089c09 in make_child (s=0x80d1f48, slot=1) at prefork.c:790 #4 0x8089c84 in startup_children (number_to_start=4) at prefork.c:808 #5 0x808a0b6 in ap_mpm_run (_pconf=0x80cf840, plog=0x8107920, s=0x80d1f48) at prefork.c:1024 #6 0x8091183 in main (argc=3, argv=0xbffff2c4) at main.c:651 #7 0x40227543 in __libc_start_main () from /lib/libc.so.6 (gdb) ----------- - Acceptable files do not call sendfile_it_all() from core_output_filter(). - Use the --without-sendfile option as a workaround for this problem (emulate_sendfile() will be called instead). - APR_TCP_NOPUSH_FLAG == 0 in this configuration - APR_TCP_NOPUSH_FLAG == TCP_CORK on a working linux system - APR_TCP_NOPUSH_FLAG == TCP_NOPUSH on a working freebsd system Conclusion: Just because sendfile() exists on the system doesn't necessarily mean that a TCP_NOPUSH variant will be available (or detected). Ways to alleviate this problem include: - better checking for TCP_CORK (the tested system _does_ support it, but the apr configure checks for TCP_CORK in netinet/tcp.h, whereas it was only in linux/tcp.h, due to old libc header files) - make TCP_NOPUSH functionality dependent on APR_TCP_NOPUSH_FLAG (and just live with any extra packets that are generated) - make the use of sendfile(2) dependent on APR_TCP_NOPUSH_FLAG (i.e. #if APR_HAS_SENDFILE && APR_TCP_NOPUSH_FLAG), in which case emulate_sendfile() will be used in its stead. Workaround: configure apache with the --without-sendfile option. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
