mirror of
https://github.com/OpenVPN/openvpn3.git
synced 2024-09-20 04:02:15 +02:00
b6b8282d33
- Used static_cast instead of direct type conversions in places where it's safe - Used numeric_cast where failure is possible - Changed types of arguments and locals when practical Signed-off-by: Charlie Vigue <charlie.vigue@openvpn.com>
138 lines
4.8 KiB
C++
138 lines
4.8 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2012-2022 OpenVPN Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License Version 3
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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// Generates ICMP "packet too big" response
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#pragma once
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#include <openvpn/common/socktypes.hpp>
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#include <openvpn/ip/csum.hpp>
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#include <openvpn/ip/ip4.hpp>
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#include <openvpn/ip/ip6.hpp>
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#include <openvpn/ip/icmp4.hpp>
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#include <openvpn/ip/icmp6.hpp>
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#include <openvpn/ip/ping6.hpp>
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#include <openvpn/ip/ipcommon.hpp>
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#include <openvpn/buffer/buffer.hpp>
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namespace openvpn {
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class Ptb
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{
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public:
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static void generate_icmp_ptb(BufferAllocated &buf, std::uint16_t nexthop_mtu)
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{
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if (buf.empty())
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return;
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switch (IPCommon::version(buf[0]))
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{
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case IPCommon::IPv4:
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if (buf.length() <= sizeof(struct IPv4Header))
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break;
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generate_icmp4_ptb(buf, nexthop_mtu);
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break;
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case IPCommon::IPv6:
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if (buf.length() <= sizeof(struct IPv6Header))
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break;
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generate_icmp6_ptb(buf, nexthop_mtu);
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break;
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}
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}
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private:
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static void generate_icmp6_ptb(BufferAllocated &buf, std::uint16_t nexthop_mtu)
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{
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// ICMPv6 data includes original IPv6 header and as many bytes of payload as possible
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auto data_size = std::min(buf.length(), std::max(sizeof(ICMPv6), static_cast<size_t>(nexthop_mtu) - sizeof(ICMPv6)));
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// sanity check
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// we use headroom for adding IPv6 + ICMPv6 headers
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if ((buf.offset() < sizeof(ICMPv6)) || (buf.capacity() < (sizeof(ICMPv6) + data_size)))
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return;
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IPv6Header *ipv6 = (IPv6Header *)buf.c_data();
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uint8_t *b = buf.prepend_alloc(sizeof(ICMPv6));
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ICMPv6 *icmp = (ICMPv6 *)b;
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// IPv6 header
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icmp->head.version_prio = (6 << 4);
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icmp->head.flow_lbl[0] = 0;
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icmp->head.flow_lbl[1] = 0;
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icmp->head.flow_lbl[2] = 0;
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icmp->head.payload_len = htons(static_cast<uint16_t>(sizeof(ICMPv6) - sizeof(IPv6Header) + data_size));
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icmp->head.nexthdr = IPCommon::ICMPv6;
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icmp->head.hop_limit = 64;
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icmp->head.saddr = ipv6->daddr;
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icmp->head.daddr = ipv6->saddr;
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// ICMP header
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icmp->type = ICMPv6::PACKET_TOO_BIG;
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icmp->code = 0;
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icmp->mtu = htonl(nexthop_mtu);
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icmp->checksum = 0;
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icmp->checksum = Ping6::csum_icmp(icmp, sizeof(ICMPv6) + data_size);
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buf.set_size(sizeof(ICMPv6) + data_size);
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}
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static void generate_icmp4_ptb(BufferAllocated &buf, std::uint16_t nexthop_mtu)
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{
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// ICMP data includes original IP header and first 8 bytes of payload
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auto data_size = sizeof(IPv4Header) + ICMPv4::MIN_DATA_SIZE;
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// sanity check
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// we use headroom for adding IPv4 + ICMPv4 headers
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if ((buf.offset() < sizeof(ICMPv4)) || (buf.capacity() < (sizeof(ICMPv4) + data_size)))
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return;
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IPv4Header *ipv4 = (IPv4Header *)buf.c_data();
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uint8_t *b = buf.prepend_alloc(sizeof(ICMPv4));
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ICMPv4 *icmp = (ICMPv4 *)b;
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icmp->head.saddr = ipv4->daddr;
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icmp->head.daddr = ipv4->saddr;
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icmp->head.version_len = IPv4Header::ver_len(IPCommon::IPv4, sizeof(IPv4Header));
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icmp->head.tos = 0;
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icmp->head.tot_len = htons(static_cast<uint16_t>(sizeof(ICMPv4) + data_size));
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icmp->head.id = 0;
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icmp->head.frag_off = 0;
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icmp->head.ttl = 64;
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icmp->head.protocol = IPCommon::ICMPv4;
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icmp->head.check = 0;
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icmp->head.check = IPChecksum::checksum(b, sizeof(IPv4Header));
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icmp->type = ICMPv4::DEST_UNREACH;
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icmp->code = ICMPv4::FRAG_NEEDED;
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icmp->unused = 0;
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icmp->nexthop_mtu = htons(nexthop_mtu);
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icmp->checksum = 0;
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icmp->checksum = IPChecksum::checksum(b + sizeof(IPv4Header), sizeof(ICMPv4) - sizeof(IPv4Header) + data_size);
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buf.set_size(sizeof(ICMPv4) + data_size);
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}
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};
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} // namespace openvpn
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