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Incoming TCP connections should not be added to the descriptor table until they're accept()ed #1780

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Incoming TCP connections should not be added to the descriptor table until they're accept()ed#1780
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Type: BugError or flaw producing unexpected results
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Validate and improve TCP simulation accuracy
@stevenengler

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@stevenengler
stevenengler
opened on Nov 19, 2021

When a listening socket receives a SYN packet, it immediately registers a new socket in the descriptor table.

shadow/src/main/host/descriptor/tcp.c

Lines 1931 to 1945 in 138b84a

switch(tcp->state) {
case TCPS_LISTEN: {
/* receive SYN, send SYNACK, move to SYNRECEIVED */
if(header->flags & PTCP_SYN) {
MAGIC_ASSERT(tcp->server);
flags |= TCP_PF_PROCESSED;
/* we need to multiplex a new child */
guint64 recvBufSize = host_getConfiguredRecvBufSize(host);
guint64 sendBufSize = host_getConfiguredSendBufSize(host);
TCP* multiplexed = tcp_new(host, recvBufSize, sendBufSize);
process_registerLegacyDescriptor(
descriptor_getOwnerProcess((LegacyDescriptor*)tcp),
(LegacyDescriptor*)multiplexed);

Shadow should wait and only register the socket in the descriptor table once the user space process calls accept().

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