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/*
* Copyright (c) 2020 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <vnet/tcp/tcp_packet.h>
#include <vnet/ip/ip4_packet.h>
always_inline void
mss_clamping (u16 mss_clamping, tcp_header_t * tcp, ip_csum_t * sum)
{
u8 *data;
u8 opt_len, opts_len, kind;
u16 mss;
if (!(mss_clamping && tcp_syn (tcp)))
return;
opts_len = (tcp_doff (tcp) << 2) - sizeof (tcp_header_t);
data = (u8 *) (tcp + 1);
for (; opts_len > 0; opts_len -= opt_len, data += opt_len)
{
kind = data[0];
if (kind == TCP_OPTION_EOL)
break;
else if (kind == TCP_OPTION_NOOP)
{
opt_len = 1;
continue;
}
else
{
if (opts_len < 2)
return;
opt_len = data[1];
if (opt_len < 2 || opt_len > opts_len)
return;
}
if (kind == TCP_OPTION_MSS)
{
mss = *(u16 *) (data + 2);
if (clib_net_to_host_u16 (mss) > mss_clamping)
{
u16 mss_value_net = clib_host_to_net_u16(mss_clamping);
*sum =
ip_csum_update (*sum, mss, mss_value_net, ip4_header_t,
length);
clib_memcpy_fast (data + 2, &mss_value_net, 2);
}
return;
}
}
}
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