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udp: limit buffer depth (#6895)

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This commit avoids OOMs on an udp corner case where a delay() in the main
loop would allow memory filling.

A memory leak has been observed with such semantically forbidden delay,
unsolved yet, and preventing to use a simple counter instead of walking
through a linked list.  The count limit is however small.
This commit is contained in:
david gauchard 2019-12-10 11:04:49 +01:00 committed by GitHub
parent 70c337001c
commit 3e6c25c21b
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1 changed files with 18 additions and 0 deletions
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18
libraries/ESP8266WiFi/src/include/UdpContext.h
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@ -265,6 +265,7 @@ public:
// ref'ing it to prevent release from the below pbuf_free(deleteme)
pbuf_ref(_rx_buf);
}
// remove the already-consumed head of the chain
pbuf_free(deleteme);
_rx_buf_offset = 0;
@ -440,6 +441,19 @@ private:
const ip_addr_t *srcaddr, u16_t srcport)
{
(void) upcb;
// check receive pbuf chain depth
{
pbuf* p;
int count = 0;
for (p = _rx_buf; p && ++count < rxBufMaxDepth*2; p = p->next);
if (p)
{
// pbuf chain too deep, dropping
pbuf_free(pb);
DEBUGV(":udr\r\n");
return;
}
}
#if LWIP_VERSION_MAJOR == 1
#define TEMPDSTADDR (&current_iphdr_dest)
@ -531,6 +545,10 @@ private:
srcaddr(src), dstaddr(dst), srcport(srcport) { }
};
AddrHelper _currentAddr;
// rx pbuf depth barrier (counter of buffered UDP received packets)
// keep it small
static constexpr int rxBufMaxDepth = 4;
};