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nic_router: forward ICMP dst unreachable messages

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This follows the guidelines in RFC 5508 to enable forwarding of ICMP
"Destination Unreachable" that correspond to an existing link state in
the NIC router. It also serves as blueprint for forwarding ICMP error
messages in general (They are merely not enabled because we don't test
them).

Issue #2732
This commit is contained in:
Martin Stein 2018-03-29 18:04:48 +02:00 committed by Christian Helmuth
parent 6a988749a1
commit 54b10b1b38
2 changed files with 74 additions and 1 deletions
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67
repos/os/src/server/nic_router/interface.cc
View File

@ -815,6 +815,70 @@ void Interface::_handle_icmp_query(Ethernet_frame &eth,
}
void Interface::_handle_icmp_error(Ethernet_frame &eth,
size_t eth_size,
Ipv4_packet &ip,
Packet_descriptor const &pkt,
Domain &local_domain,
Icmp_packet &icmp,
size_t icmp_sz)
{
/* drop packet if embedded IP checksum invalid */
size_t const embed_ip_sz = icmp_sz - sizeof(Icmp_packet);
Ipv4_packet &embed_ip = icmp.data<Ipv4_packet>(embed_ip_sz);
if (Ipv4_packet::calculate_checksum(embed_ip) != embed_ip.checksum()) {
throw Drop_packet_inform("bad checksum in IP packet embedded in ICMP error");
}
/* get link identity of the embeddeded transport packet */
L3_protocol const embed_prot = embed_ip.protocol();
size_t const embed_prot_size = embed_ip.total_length() - embed_ip.header_length() * 4;
void *const embed_prot_base = _prot_base(embed_prot, embed_prot_size, embed_ip);
Link_side_id const local_id = { embed_ip.dst(), _dst_port(embed_prot, embed_prot_base),
embed_ip.src(), _src_port(embed_prot, embed_prot_base) };
try {
/* lookup a link state that matches the embedded transport packet */
Link_side const &local_side = local_domain.links(embed_prot).find_by_id(local_id);
Link &link = local_side.link();
bool const client = local_side.is_client();
Link_side &remote_side = client ? link.server() : link.client();
Domain &remote_domain = remote_side.domain();
/* print out that the link is used */
if (_config().verbose()) {
log("Using ", l3_protocol_name(embed_prot), " link: ", link); }
/* adapt source and destination of Ethernet frame and IP packet */
_adapt_eth(eth, remote_side.src_ip(), pkt, remote_domain);
if (remote_side.dst_ip() == remote_domain.ip_config().interface.address) {
ip.src(remote_side.dst_ip());
}
ip.dst(remote_side.src_ip());
/* adapt source and destination of embedded IP and transport packet */
embed_ip.src(remote_side.src_ip());
embed_ip.dst(remote_side.dst_ip());
_src_port(embed_prot, embed_prot_base, remote_side.src_port());
_dst_port(embed_prot, embed_prot_base, remote_side.dst_port());
/* update checksum of both IP headers and the ICMP header */
embed_ip.checksum(Ipv4_packet::calculate_checksum(embed_ip));
icmp.checksum(icmp.calc_checksum(icmp_sz - sizeof(Icmp_packet)));
ip.checksum(Ipv4_packet::calculate_checksum(ip));
/* send adapted packet to all interfaces of remote domain */
remote_domain.interfaces().for_each([&] (Interface &interface) {
interface.send(eth, eth_size);
});
/* refresh link only if the error is not about an ICMP query */
if (embed_prot != L3_protocol::ICMP) {
_link_packet(embed_prot, embed_prot_base, link, client); }
}
/* drop packet if there is no matching link */
catch (Link_side_tree::No_match) {
throw Drop_packet_inform("no link that matches packet embedded in ICMP error"); }
}
void Interface::_handle_icmp(Ethernet_frame &eth,
size_t eth_size,
Ipv4_packet &ip,
@ -834,7 +898,8 @@ void Interface::_handle_icmp(Ethernet_frame &eth,
/* select ICMP message type */
switch (icmp.type()) {
case Icmp_packet::Type::ECHO_REPLY:
case Icmp_packet::Type::ECHO_REQUEST: _handle_icmp_query(eth, eth_size, ip, pkt, prot, prot_base, prot_size, local_domain); break;
case Icmp_packet::Type::ECHO_REQUEST: _handle_icmp_query(eth, eth_size, ip, pkt, prot, prot_base, prot_size, local_domain); break;
case Icmp_packet::Type::DST_UNREACHABLE: _handle_icmp_error(eth, eth_size, ip, pkt, local_domain, icmp, icmp_sz); break;
default: Drop_packet_inform("unknown ICMP message type"); }
}

8
repos/os/src/server/nic_router/interface.h
View File

@ -169,6 +169,14 @@ class Net::Interface : private Interface_list::Element
Genode::size_t prot_size,
Domain &local_domain);
void _handle_icmp_error(Ethernet_frame &eth,
Genode::size_t eth_size,
Ipv4_packet &ip,
Packet_descriptor const &pkt,
Domain &local_domain,
Icmp_packet &icmp,
Genode::size_t icmp_sz);
void _handle_icmp(Ethernet_frame &eth,
Genode::size_t eth_size,
Ipv4_packet &ip,