[stunnel-users] stunnel 4.14 died silently under traffic stress test

[Michal Trojnara]

Zhuang Yuyao wrote:
> I am still trying to find another better solution: let kernel to send 
> stunnel a signal while available memory is under a special threshold, 
> then stunnel will stop accepting new connections and try to 
> release some memory (kill the latest created threads?)
> until kernel notifies us the available memory is increased
> and enough for new connections/threads.

Sounds like a crazy idea to me.  8-)

Monitoring available memory creates an obvious race condition (with other
processes using the same memory) unless you're going to do it in kernel.
8-)))

BTW: Stunnel itself should work fine with OOM killer turned off.
I'm not so sure about its libraries.

$ egrep -A 2 '(malloc)|(calloc)|(realloc)' *.c
client.c:    c=calloc(1, sizeof(CLI));
client.c-    if(!c) {
client.c-        s_log(LOG_ERR, "Memory allocation failed");
--
ctx.c:        cp=malloc(n+1);
ctx.c-        n=BIO_read(bio, cp, n);
ctx.c-        cp[n]='\0';
--
file.c:    df=calloc(1, sizeof(DISK_FILE));
file.c-    if(!df)
file.c-        return NULL;
--
file.c:    df=calloc(1, sizeof(DISK_FILE));
file.c-    if(!df)
file.c-        return NULL;
--
file.c:    buff=calloc(len+2, 1); /* +2 for \r\n */
file.c-    if(!buff)
file.c-        return 0;
--
file.c:    out=malloc((len+1)*sizeof(WCHAR));
file.c-    if(!out)
file.c-        return NULL;
--
file.c:    out=malloc(len+1);
file.c-    if(!out)
file.c-        return NULL;
--
file.c:    out=malloc(len+1);
file.c-    if(!out)
file.c-        return NULL;
--
file.c:    out=malloc(len+1);
file.c-    if(!out)
file.c-        return NULL;
--
gui.c:    curr=malloc(sizeof(struct LIST)+len*sizeof(TCHAR));
gui.c-    curr->len=len;
gui.c-    _tcscpy(curr->txt, txt);
--
gui.c:    buff=malloc((len+1)*sizeof(TCHAR)); /* +1 for trailing '\0' */
gui.c-    for(curr=head; curr; curr=curr->next) {
gui.c-        memcpy(buff+ptr, curr->txt, curr->len*sizeof(TCHAR));
--
network.c:        ufds=realloc(ufds, nfds*sizeof(struct pollfd));
network.c-        if(!ufds) {
network.c-            s_log(LOG_CRIT, "Memory allocation failed");
--
options.c:            new_section=calloc(1, sizeof(LOCAL_OPTIONS));
options.c-            if(!new_section) {
options.c-                log_raw("Fatal memory allocation error");
--
options.c:    retval=calloc(strlen(str)+1, 1);
options.c-    if(!retval) {
options.c-        log_raw("Fatal memory allocation error");
--
options.c:    retval=calloc(len+1, 1);
options.c-    if(!retval) {
options.c-        log_raw("Fatal memory allocation error");
--
options.c:    retval=calloc(max_arg+1, sizeof(char *));
options.c-    if(!retval) {
options.c-        log_raw("Fatal memory allocation error");
--
options.c:    ptr->opt_val[socket_type]=calloc(1, sizeof(OPT_UNION));
options.c-    switch(ptr->opt_type) {
options.c-    case TYPE_FLAG:
--
resolver.c:    ai=calloc(1, sizeof(struct addrinfo));
resolver.c-    if(!ai)
resolver.c-        return EAI_MEMORY;
--
resolver.c:    ai->ai_addr=calloc(1, ai->ai_addrlen);
resolver.c-    if(!ai->ai_addr) {
resolver.c-        free(ai);
--
resolver.c:    ai->ai_addr=calloc(1, ai->ai_addrlen);
resolver.c-    if(!ai->ai_addr) {
resolver.c-        free(ai);
--
resolver.c:        ai=calloc(1, sizeof(struct addrinfo));
resolver.c-        if(!ai)
resolver.c-            return EAI_MEMORY;
--
resolver.c:            ai->ai_addr=calloc(1, ai->ai_addrlen);
resolver.c-            if(!ai->ai_addr)
resolver.c-                return EAI_MEMORY;
--
resolver.c:            ai->ai_addr=calloc(1, ai->ai_addrlen);
resolver.c-            if(!ai->ai_addr)
resolver.c-                return EAI_MEMORY;
--
sthreads.c:    ctx=malloc(sizeof(CONTEXT));
sthreads.c-    if(!ctx) {
sthreads.c-        s_log(LOG_ERR, "Unable to allocate CONTEXT structure");

Best regards,
    Mike