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Merge pull request #4762 from mpg/fix-overly-aggressive-udp-proxy-2.x

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[Backport 2.x] Fix bug with UDP proxy not forwarding enough
This commit is contained in:
Gilles Peskine 2021-07-09 11:57:52 +02:00 committed by GitHub
commit 8de3633c65
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 18 additions and 22 deletions
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40
programs/test/udp_proxy.c
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@ -683,26 +683,21 @@ int send_delayed()
}
/*
* Avoid dropping or delaying a packet that was already dropped twice: this
* only results in uninteresting timeouts. We can't rely on type to identify
* packets, since during renegotiation they're all encrypted. So, rely on
* size mod 2048 (which is usually just size).
*/
static unsigned char dropped[2048] = { 0 };
#define DROP_MAX 2
/* We only drop packets at the level of entire datagrams, not at the level
* Avoid dropping or delaying a packet that was already dropped or delayed
* ("held") twice: this only results in uninteresting timeouts. We can't rely
* on type to identify packets, since during renegotiation they're all
* encrypted. So, rely on size mod 2048 (which is usually just size).
*
* We only hold packets at the level of entire datagrams, not at the level
* of records. In particular, if the peer changes the way it packs multiple
* records into a single datagram, we don't necessarily count the number of
* times a record has been dropped correctly. However, the only known reason
* times a record has been held correctly. However, the only known reason
* why a peer would change datagram packing is disabling the latter on
* retransmission, in which case we'd drop involved records at most
* DROP_MAX + 1 times. */
void update_dropped( const packet *p )
{
size_t id = p->len % sizeof( dropped );
++dropped[id];
}
* retransmission, in which case we'd hold involved records at most
* HOLD_MAX + 1 times.
*/
static unsigned char held[2048] = { 0 };
#define HOLD_MAX 2
int handle_message( const char *way,
mbedtls_net_context *dst,
@ -729,7 +724,7 @@ int handle_message( const char *way,
cur.dst = dst;
print_packet( &cur, NULL );
id = cur.len % sizeof( dropped );
id = cur.len % sizeof( held );
if( strcmp( way, "S <- C" ) == 0 )
{
@ -771,10 +766,10 @@ int handle_message( const char *way,
! ( opt.protect_hvr &&
strcmp( cur.type, "HelloVerifyRequest" ) == 0 ) &&
cur.len != (size_t) opt.protect_len &&
dropped[id] < DROP_MAX &&
held[id] < HOLD_MAX &&
rand() % opt.drop == 0 ) )
{
update_dropped( &cur );
++held[id];
}
else if( ( opt.delay_ccs == 1 &&
strcmp( cur.type, "ChangeCipherSpec" ) == 0 ) ||
@ -784,9 +779,10 @@ int handle_message( const char *way,
! ( opt.protect_hvr &&
strcmp( cur.type, "HelloVerifyRequest" ) == 0 ) &&
cur.len != (size_t) opt.protect_len &&
dropped[id] < DROP_MAX &&
held[id] < HOLD_MAX &&
rand() % opt.delay == 0 ) )
{
++held[id];
delay_packet( &cur );
}
else
@ -897,7 +893,7 @@ accept:
* 3. Forward packets forever (kill the process to terminate it)
*/
clear_pending();
memset( dropped, 0, sizeof( dropped ) );
memset( held, 0, sizeof( held ) );
nb_fds = client_fd.fd;
if( nb_fds < server_fd.fd )