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3f36fe9c2

Denys Vlasenko
Denys Vlasenko
2026-01-22
SUCCESS Duration: 143s

Subject

httpd: add -M MAXCONN - do not accept unlimited number of connections

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0 
gcc -Wp,-MD,applets/.usage.d -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer      -Iinclude -Iinclude -o applets/usage applets/usage.c

Build Log

(log yok)

Commit Diff GitHub →

networking/httpd.c +86 -19
networking/httpd.c+86 -19
@@ -267,6 +267,7 @@
//usage: "[-ifv[v]]"
//usage: " [-c CONFFILE]"
//usage: " [-p [IP:]PORT]"
+//usage: " [-M MAXCONN]"
//usage: IF_FEATURE_HTTPD_SETUID(" [-u USER[:GRP]]")
//usage: IF_FEATURE_HTTPD_BASIC_AUTH(" [-r REALM]")
//usage: " [-h HOME]\n"
@@ -277,6 +278,7 @@
//usage: "\n -f Run in foreground"
//usage: "\n -v[v] Verbose"
//usage: "\n -p [IP:]PORT Bind to IP:PORT (default *:"STR(CONFIG_FEATURE_HTTPD_PORT_DEFAULT)")"
+//usage: "\n -M NUM Pause if NUM connections are open (default 256)"
//usage: IF_FEATURE_HTTPD_SETUID(
//usage: "\n -u USER[:GRP] Set uid/gid after binding to port")
//usage: IF_FEATURE_HTTPD_BASIC_AUTH(
@@ -479,6 +481,8 @@ struct globals {
IF_FEATURE_HTTPD_BASIC_AUTH(char *remoteuser;)
pid_t parent_pid;
+ int children_fd;
+ int conn_limit;
off_t file_size; /* -1 - unknown */
#if ENABLE_FEATURE_HTTPD_RANGES
@@ -494,7 +498,6 @@ struct globals {
#if ENABLE_FEATURE_HTTPD_CONFIG_WITH_SCRIPT_INTERPR
Htaccess *script_i; /* config script interpreters */
#endif
- char *iobuf; /* [IOBUF_SIZE] */
#define hdr_buf bb_common_bufsiz1
#define sizeof_hdr_buf COMMON_BUFSIZE
char *hdr_ptr;
@@ -508,6 +511,7 @@ struct globals {
#if ENABLE_FEATURE_HTTPD_PROXY
Htaccess_Proxy *proxy;
#endif
+ char iobuf[IOBUF_SIZE];
};
#define G (*ptr_to_globals)
#define verbose (G.verbose )
@@ -543,11 +547,11 @@ enum {
#define g_auth (G.g_auth )
#define mime_a (G.mime_a )
#define script_i (G.script_i )
-#define iobuf (G.iobuf )
#define hdr_ptr (G.hdr_ptr )
#define hdr_cnt (G.hdr_cnt )
#define http_error_page (G.http_error_page )
#define proxy (G.proxy )
+#define iobuf (G.iobuf )
#define INIT_G() do { \
setup_common_bufsiz(); \
SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
@@ -1045,7 +1049,8 @@ static void decodeBase64(char *data)
*/
static int openServer(void)
{
- unsigned n = bb_strtou(bind_addr_or_port, NULL, 10);
+ unsigned n;
+ n = bb_strtou(bind_addr_or_port, NULL, 10);
if (!errno && n && n <= 0xffff)
n = create_and_bind_stream_or_die(NULL, n);
else
@@ -2227,10 +2232,6 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
#endif
char *HTTP_slash;
- /* Allocation of iobuf is postponed until now
- * (IOW, server process doesn't need to waste 8k) */
- iobuf = xmalloc(IOBUF_SIZE);
-
if (ENABLE_FEATURE_HTTPD_CGI || DEBUG || verbose) {
/* NB: can be NULL (user runs httpd -i by hand?) */
rmt_ip_str = xmalloc_sockaddr2dotted(&fromAddr->u.sa);
@@ -2643,6 +2644,57 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
);
}
+static int count_children(void)
+{
+ int count;
+ int sz = pread(G.children_fd, iobuf, IOBUF_SIZE - 1, 0);
+ if (sz < 0)
+ return -1;
+ /* The actual format is "NUM NUM ", but future-proof for lack of last space, and for '\n' */
+ count = 0;
+ if (sz > 0) {
+ char *p = iobuf;
+ iobuf[sz] = '\n';
+ do {
+ if (*++p == ' ')
+ count++, p++;
+ } while (*p != '\n');
+ if (p[-1] != ' ') /* it was "NUM NUM\n" (not "NUM NUM \n")? */
+ count++; /* there were (NUMSPACES + 1) pids */
+ }
+ return count;
+}
+
+static int throttle_if_conn_limit(void)
+{
+ unsigned usec = 0xffff; /* 0.065535 seconds */
+ int countdown, c;
+ for (;;) {
+ countdown = G.conn_limit;
+ c = count_children();
+ if (c < 0)
+ break; /* can't count them */
+ countdown -= c;
+ if (countdown <= 0) { /* we are at MAXCONN, pause until we are below */
+ bb_error_msg("pausing, children:%u", c);
+ //bb_error_msg("pausing %ums, children:%u", usec/1000, c);
+ usleep(usec);
+ usec = ((usec << 1) | 1) & 0x1fffff; /* x2, up to 2.097151 seconds */
+ continue; /* loop: count them again */
+ }
+ if (VERBOSE_3) /* -vvv periodically shows # of children */
+ bb_error_msg("children:%u", c ? c - 1 : c);
+// "Why minus one?!" you ask. We _just now_ forked (see the caller)
+// and immediately checked the # of children.
+// Of course, the just-forked child did not have time to complete.
+// Without "minus one" hack, this causes above statement to always show
+// at least one child, gives wrong impression to the log's reader
+// (looks like one child is stuck).
+ break;
+ }
+ return countdown;
+}
+
/*
* The main http server function.
* Given a socket, listen for new connections and farm out
@@ -2653,16 +2705,22 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
static void mini_httpd(int server_socket) NORETURN;
static void mini_httpd(int server_socket)
{
+ int countdown;
+
xmove_fd(server_socket, 0);
/* NB: it's best to not use xfuncs in this loop before fork().
* Otherwise server may die on transient errors (temporary
* out-of-memory condition, etc), which is Bad(tm).
* Try to do any dangerous calls after fork.
*/
+ countdown = G.conn_limit;
while (1) {
int n;
len_and_sockaddr fromAddr;
+ if (G.children_fd > 0 && --countdown < 0)
+ countdown = throttle_if_conn_limit();
+
/* Wait for connections... */
fromAddr.len = LSA_SIZEOF_SA;
n = accept(0, &fromAddr.u.sa, &fromAddr.len);
@@ -2698,6 +2756,7 @@ static void mini_httpd(int server_socket)
static void mini_httpd_nommu(int server_socket, int argc, char **argv) NORETURN;
static void mini_httpd_nommu(int server_socket, int argc, char **argv)
{
+ int countdown;
char *argv_copy[argc + 2];
argv_copy[0] = argv[0];
@@ -2710,9 +2769,13 @@ static void mini_httpd_nommu(int server_socket, int argc, char **argv)
* out-of-memory condition, etc), which is Bad(tm).
* Try to do any dangerous calls after fork.
*/
+ countdown = G.conn_limit;
while (1) {
int n;
+ if (G.children_fd > 0 && --countdown < 0)
+ countdown = throttle_if_conn_limit();
+
/* Wait for connections... */
n = accept(0, NULL, NULL);
if (n < 0)
@@ -2774,9 +2837,10 @@ enum {
IF_FEATURE_HTTPD_AUTH_MD5( m_opt_md5 ,)
IF_FEATURE_HTTPD_SETUID( u_opt_setuid ,)
p_opt_port ,
- p_opt_inetd ,
- p_opt_foreground,
- p_opt_verbose ,
+ M_opt_maxconn ,
+ i_opt_inetd ,
+ f_opt_foreground,
+ v_opt_verbose ,
OPT_CONFIG_FILE = 1 << c_opt_config_file,
OPT_DECODE_URL = 1 << d_opt_decode_url,
OPT_HOME_HTTPD = 1 << h_opt_home_httpd,
@@ -2785,9 +2849,9 @@ enum {
OPT_MD5 = IF_FEATURE_HTTPD_AUTH_MD5( (1 << m_opt_md5 )) + 0,
OPT_SETUID = IF_FEATURE_HTTPD_SETUID( (1 << u_opt_setuid )) + 0,
OPT_PORT = 1 << p_opt_port,
- OPT_INETD = 1 << p_opt_inetd,
- OPT_FOREGROUND = 1 << p_opt_foreground,
- OPT_VERBOSE = 1 << p_opt_verbose,
+ OPT_INETD = 1 << i_opt_inetd,
+ OPT_FOREGROUND = 1 << f_opt_foreground,
+ OPT_VERBOSE = 1 << v_opt_verbose,
};
@@ -2809,6 +2873,7 @@ int httpd_main(int argc UNUSED_PARAM, char **argv)
setlocale(LC_TIME, "C");
#endif
+ G.conn_limit = 256;
home_httpd = xrealloc_getcwd_or_warn(NULL);
/* We do not "absolutize" path given by -h (home) opt.
* If user gives relative path in -h,
@@ -2819,7 +2884,7 @@ int httpd_main(int argc UNUSED_PARAM, char **argv)
IF_FEATURE_HTTPD_BASIC_AUTH("r:")
IF_FEATURE_HTTPD_AUTH_MD5("m:")
IF_FEATURE_HTTPD_SETUID("u:")
- "p:ifv"
+ "p:M:+ifv"
"\0"
/* -v counts, -i implies -f */
"vv:if",
@@ -2829,6 +2894,7 @@ int httpd_main(int argc UNUSED_PARAM, char **argv)
IF_FEATURE_HTTPD_AUTH_MD5(, &pass)
IF_FEATURE_HTTPD_SETUID(, &s_ugid)
, &bind_addr_or_port
+ , &G.conn_limit
, &verbose
);
if (opt & OPT_DECODE_URL) {
@@ -2871,6 +2937,10 @@ int httpd_main(int argc UNUSED_PARAM, char **argv)
xchdir(home_httpd);
if (!(opt & OPT_INETD)) {
+ G.parent_pid = getpid();
+ sprintf(iobuf, "/proc/self/task/%u/children", (unsigned)G.parent_pid);
+ G.children_fd = open(iobuf, O_RDONLY | O_CLOEXEC);
+
/* Make it unnecessary to wait for children */
signal(SIGCHLD, SIG_IGN);
@@ -2905,16 +2975,13 @@ int httpd_main(int argc UNUSED_PARAM, char **argv)
// setenv_long("SERVER_PORT", ???);
}
#endif
-
parse_conf(DEFAULT_PATH_HTTPD_CONF, FIRST_PARSE);
- if (!(opt & OPT_INETD)) {
- G.parent_pid = getpid();
- signal(SIGHUP, sighup_handler);
- }
xfunc_error_retval = 0;
if (opt & OPT_INETD)
mini_httpd_inetd(); /* never returns */
+
+ signal(SIGHUP, sighup_handler);
#if BB_MMU
if (!(opt & OPT_FOREGROUND))
bb_daemonize(0); /* don't change current directory */