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* tap: Don't quit if pasta gets EIO on writev() to tap, interface might be downStefano Brivio2024-07-251-0/+1
| | | | | | | | | | | | | | | | | | | | | | | If we start pasta with some ports forwarded, but no --config-net, say: $ ./pasta -u 10001 and then use a local, non-loopback address to send traffic to that port, say: $ socat -u FILE:test UDP4:192.0.2.1:10001 pasta writes to the tap file descriptor, but if the interface is down, we get EIO and terminate. By itself, what I'm doing in this case is not very useful (I simply forgot to pass --config-net), but if we happen to have a DHCP client in the network namespace, the interface might still be down while somebody tries to send traffic to it, and exiting in that case is not really helpful. Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
* tcp: Correctly update SO_PEEK_OFF when tcp_send_frames() drops framesDavid Gibson2024-07-242-10/+15
| | | | | | | | | | | | | | | | | | When using the new SO_PEEK_OFF feature on TCP sockets, we must adjust the SO_PEEK_OFF value whenever we move conn->seq_to_tap backwards. Although it was discussed during development, somewhere during the shuffles the case where we move the pointer backwards because we lost frames while sending them to the guest. This can happen, for example, if the socket buffer on the Unix socket to qemu overflows. Fixing this is slightly complicated because we need to pass a non-const context pointer to some places we previously didn't need it. While we're there also fix a small stylistic issue in the function comment for tcp_revert_seq() - it was using spaces instead of tabs. Fixes: e63d281871ef ("tcp: leverage support of SO_PEEK_OFF socket option when available") Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: probe for SO_PEEK_OFF both in tcpv4 and tcp6Jon Maloy2024-07-231-12/+25
| | | | | | | | | | | | | | | | | | | Based on an original patch by Jon Maloy: -- The recently added socket option SO_PEEK_OFF is not supported for TCP/IPv6 sockets. Until we get that support into the kernel we need to test for support in both protocols to set the global 'peek_offset_cap´ to true. -- Compared to the original patch: - only check for SO_PEEK_OFF support for enabled IP versions - use sa_family_t instead of int to pass the address family around Fixes: e63d281871ef ("tcp: leverage support of SO_PEEK_OFF socket option when available") Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
* udp: Rename UDP listening socketsDavid Gibson2024-07-196-28/+23
| | | | | | | | | | EPOLL_TYPE_UDP is now only used for "listening" sockets; long lived sockets which can initiate new flows. Rename to EPOLL_TYPE_UDP_LISTEN and associated functions to match. Along with that, remove the .orig field from union udp_listen_epoll_ref, since it is now always true. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Remove rdelta port forwarding mapsDavid Gibson2024-07-194-67/+27
| | | | | | | | | | | | | | | | In addition to the struct fwd_ports used by both UDP and TCP to track port forwarding, UDP also included an 'rdelta' field, which contained the reverse mapping of the main port map. This was used so that we could properly direct reply packets to a forwarded packet where we change the destination port. This has now been taken over by the flow table: reply packets will match the flow of the originating packet, and that gives the correct ports on the originating side. So, eliminate the rdelta field, and with it struct udp_fwd_ports, which now has no additional information over struct fwd_ports. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Remove obsolete socket trackingDavid Gibson2024-07-191-91/+1
| | | | | | | | | Now that UDP datagrams are all directed via the flow table, we no longer use the udp_tap_map[ or udp_act[] arrays. Remove them and connected code. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Direct datagrams from host to guest via flow tableDavid Gibson2024-07-191-134/+51
| | | | | | | | | | | This replaces the last piece of existing UDP port tracking with the common flow table. Specifically use the flow table to direct datagrams from host sockets to the guest tap interface. Since this now requires a flow for every datagram, we add some logging if we encounter any datagrams for which we can't find or create a flow. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Find or create flows for datagrams from tap interfaceDavid Gibson2024-07-193-117/+100
| | | | | | | | | | | | | | | | | | | | | | Currently we create flows for datagrams from socket interfaces, and use them to direct "spliced" (socket to socket) datagrams. We don't yet match datagrams from the tap interface to existing flows, nor create new flows for them. Add that functionality, matching datagrams from tap to existing flows when they exist, or creating new ones. As with spliced flows, when creating a new flow from tap to socket, we create a new connected socket to receive reply datagrams attached to that flow specifically. We extend udp_flow_sock_handler() to handle reply packets bound for tap rather than another socket. For non-obvious reasons (perhaps increased stack usage?), this caused a failure for me when running under valgrind, because valgrind invoked rt_sigreturn which is not in our seccomp filter. Since we already allow rt_sigaction and others in the valgrind target, it seems reasonable to add rt_sigreturn as well. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Remove obsolete splice trackingDavid Gibson2024-07-192-51/+19
| | | | | | | | | | | | | | | Now that spliced datagrams are managed via the flow table, remove UDP_ACT_SPLICE_NS and UDP_ACT_SPLICE_INIT which are no longer used. With those removed, the 'ts' field in udp_splice_port is also no longer used. struct udp_splice_port now contains just a socket fd, so replace it with a plain int in udp_splice_ns[] and udp_splice_init[]. The latter are still used for tracking of automatic port forwarding. Finally, the 'splice' field of union udp_epoll_ref is no longer used so remove it as well. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Handle "spliced" datagrams with per-flow socketsDavid Gibson2024-07-199-264/+226
| | | | | | | | | | | | | | | | | | | | | When forwarding a datagram to a socket, we need to find a socket with a suitable local address to send it. Currently we keep track of such sockets in an array indexed by local port, but this can't properly handle cases where we have multiple local addresses in active use. For "spliced" (socket to socket) cases, improve this by instead opening a socket specifically for the target side of the flow. We connect() as well as bind()ing that socket, so that it will only receive the flow's reply packets, not anything else. We direct datagrams sent via that socket using the addresses from the flow table, effectively replacing bespoke addressing logic with the unified logic in fwd.c When we create the flow, we also take a duplicate of the originating socket, and use that to deliver reply datagrams back to the origin, again using addresses from the flow table entry. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Create flows for datagrams from originating socketsDavid Gibson2024-07-196-5/+242
| | | | | | | | | | | | | | | | This implements the first steps of tracking UDP packets with the flow table rather than its own (buggy) set of port maps. Specifically we create flow table entries for datagrams received from a socket (PIF_HOST or PIF_SPLICE). When splitting datagrams from sockets into batches, we group by the flow as well as splicesrc. This may result in smaller batches, but makes things easier down the line. We can re-optimise this later if necessary. For now we don't do anything else with the flow, not even match reply packets to the same flow. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* fwd: Update flow forwarding logic for UDPDavid Gibson2024-07-191-4/+23
| | | | | | | | | | | Add logic to the fwd_nat_from_*() functions to forwarding UDP packets. The logic here doesn't exactly match our current forwarding, since our current forwarding has some very strange and buggy edge cases. Instead it's attempting to replicate what appears to be the intended logic behind the current forwarding. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow, icmp: Use general flow forwarding rules for ICMPDavid Gibson2024-07-192-38/+10
| | | | | | | | | | | | | | | | | Current ICMP hard codes its forwarding rules, and never applies any translations. Change it to use the flow_target() function, so that it's translated the same as TCP (excluding TCP specific port redirection). This means that gw mapping now applies to ICMP so "ping <gw address>" will now ping the host's loopback instead of the actual gw machine. This removes the surprising behaviour that the target you ping might not be the same as you connect to with TCP. This removes the last user of flow_target_af(), so that's removed as well. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow, tcp: Flow based NAT and port forwarding for TCPDavid Gibson2024-07-197-139/+245
| | | | | | | | | | | | | | | | | | Currently the code to translate host side addresses and ports to guest side addresses and ports, and vice versa, is scattered across the TCP code. This includes both port redirection as controlled by the -t and -T options, and our special case NAT controlled by the --no-map-gw option. Gather this logic into fwd_nat_from_*() functions for each input interface in fwd.c which take protocol and address information for the initiating side and generates the pif and address information for the forwarded side. This performs any NAT or port forwarding needed. We create a flow_target() helper which applies those forwarding functions as needed to automatically move a flow from INI to TGT state. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* icmp: Manage outbound socket address via flow tableDavid Gibson2024-07-192-14/+10
| | | | | | | | | | | | | | | | | | | | | | | | | For now when we forward a ping to the host we leave the host side forwarding address and port blank since we don't necessarily know what source address and id will be used by the kernel. When the outbound address option is active, though, we do know the address at least, so we can record it in the flowside. Having done that, use it as the primary source of truth, binding the outgoing socket based on the information in there. This allows the possibility of more complex rules for what outbound address and/or id we use in future. To implement this we create a new helper which sets up a new socket based on information in a flowside, which will also have future uses. It behaves slightly differently from the existing ICMP code, in that it doesn't bind to a specific interface if given a loopback address. This is logically correct - the loopback address means we need to operate through the host's loopback interface, not ifname_out. We didn't need it in ICMP because ICMP will never generate a loopback address at this point, however we intend to change that in future. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow: Helper to create sockets based on flowsideDavid Gibson2024-07-194-3/+102
| | | | | | | | | We have upcoming use cases where it's useful to create new bound socket based on information from the flow table. Add flowside_sock_l4() to do this for either PIF_HOST or PIF_SPLICE sockets. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* icmp: Eliminate icmp_id_mapDavid Gibson2024-07-191-17/+2
| | | | | | | | With previous reworks the icmp_id_map data structure is now maintained, but never used for anything. Eliminate it. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* icmp: Look up ping flows using flow hashDavid Gibson2024-07-191-3/+15
| | | | | | | | | | When we receive a ping packet from the tap interface, we currently locate the correct flow entry (if present) using an anciliary data structure, the icmp_id_map[] tables. However, we can look this up using the flow hash table - that's what it's for. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* icmp: Obtain destination addresses from the flowsidesDavid Gibson2024-07-193-22/+17
| | | | | | | | | | | | | | | | | icmp_sock_handler() obtains the guest address from it's most recently observed IP. However, this can now be obtained from the common flowside information. icmp_tap_handler() builds its socket address for sendto() directly from the destination address supplied by the incoming tap packet. This can instead be generated from the flow. Using the flowsides as the common source of truth here prepares us for allowing more flexible NAT and forwarding by properly initialising that flowside information. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* icmp: Remove redundant id field from flow table entryDavid Gibson2024-07-192-7/+5
| | | | | | | | | struct icmp_ping_flow contains a field for the ICMP id of the ping, but this is now redundant, since the id is also stored as the "port" in the common flowsides. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: Re-use flow hash for initial sequence number generationDavid Gibson2024-07-193-29/+36
| | | | | | | | | | | | | | | | | We generate TCP initial sequence numbers, when we need them, from a hash of the source and destination addresses and ports, plus a timestamp. Moments later, we generate another hash of the same information plus some more to insert the connection into the flow hash table. With some tweaks to the flow_hash_insert() interface and changing the order we can re-use that hash table hash for the initial sequence number, rather than calculating another one. It won't generate identical results, but that doesn't matter as long as the sequence numbers are well scattered. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow, tcp: Generalise TCP hash table to general flow hash tableDavid Gibson2024-07-195-145/+172
| | | | | | | | | | | | | | | | Move the data structures and helper functions for the TCP hash table to flow.c, making it a general hash table indexing sides of flows. This is largely code motion and straightforward renames. There are two semantic changes: * flow_lookup_af() now needs to verify that the entry has a matching protocol and interface as well as matching addresses and ports. * We double the size of the hash table, because it's now at least theoretically possible for both sides of each flow to be hashed. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp, flow: Replace TCP specific hash function with general flow hashDavid Gibson2024-07-194-53/+65
| | | | | | | | | | | | | | | | Currently we match TCP packets received on the tap connection to a TCP connection via a hash table based on the forwarding address and both ports. We hope in future to allow for multiple guest side addresses, or for multiple interfaces which means we may need to distinguish based on the endpoint address and pif as well. We also want a unified hash table to cover multiple protocols, not just TCP. Replace the TCP specific hash function with one suitable for general flows, or rather for one side of a general flow. This includes all the information from struct flowside, plus the pif and the L4 protocol number. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp_splice: Eliminate SPLICE_V6 flagDavid Gibson2024-07-192-7/+3
| | | | | | | | | | | | | Since we're now constructing socket addresses based on information in the flowside, we no longer need an explicit flag to tell if we're dealing with an IPv4 or IPv6 connection. Hence, drop the now unused SPLICE_V6 flag. As well as just simplifying the code, this allows for possible future extensions where we could splice an IPv4 connection to an IPv6 connection or vice versa. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: Simplify endpoint validation using flowside informationDavid Gibson2024-07-192-55/+18
| | | | | | | | Now that we store all our endpoints in the flowside structure, use some inany helpers to make validation of those endpoints simpler. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: Manage outbound address via flow tableDavid Gibson2024-07-191-43/+50
| | | | | | | | | | | | | | | | For now when we forward a connection to the host we leave the host side forwarding address and port blank since we don't necessarily know what source address and port will be used by the kernel. When the outbound address option is active, though, we do know the address at least, so we can record it in the flowside. Having done that, use it as the primary source of truth, binding the outgoing socket based on the information in there. This allows the possibility of more complex rules for what outbound address and/or port we use in future. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: Obtain guest address from flowsideDavid Gibson2024-07-193-33/+17
| | | | | | | | | | | | | | | | Currently we always deliver inbound TCP packets to the guest's most recent observed IP address. This has the odd side effect that if the guest changes its IP address with active TCP connections we might deliver packets from old connections to the new address. That won't work; it will probably result in an RST from the guest. Worse, if the guest added a new address but also retains the old one, then we could break those old connections by redirecting them to the new address. Now that we maintain flowside information, we have a record of the correct guest side address and can just use it. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp, flow: Remove redundant information, repack connection structuresDavid Gibson2024-07-193-51/+47
| | | | | | | | | | | Some information we explicitly store in the TCP connection is now duplicated in the common flow structure. Access it from there instead, and remove it from the TCP specific structure. With that done we can reorder both the "tap" and "splice" TCP structures a bit to get better packing for the new combined flow table entries. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow: Common address information for target sideDavid Gibson2024-07-198-78/+153
| | | | | | | | | | | | | | | Require the address and port information for the target (non initiating) side to be populated when a flow enters TGT state. Implement that for TCP and ICMP. For now this leaves some information redundantly recorded in both generic and type specific fields. We'll fix that in later patches. For TCP we now use the information from the flow to construct the destination socket address in both tcp_conn_from_tap() and tcp_splice_connect(). Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow: Common address information for initiating sideDavid Gibson2024-07-196-11/+127
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Handling of each protocol needs some degree of tracking of the addresses and ports at the end of each connection or flow. Sometimes that's explicit (as in the guest visible addresses for TCP connections), sometimes implicit (the bound and connected addresses of sockets). To allow more consistent handling across protocols we want to uniformly track the address and port at each end of the connection. Furthermore, because we allow port remapping, and we sometimes need to apply NAT, the addresses and ports can be different as seen by the guest/namespace and as by the host. Introduce 'struct flowside' to keep track of address and port information related to one side of a flow. Store two of these in the common fields of a flow to track that information for both sides. For now we only populate the initiating side, requiring that information be completed when a flows enter INI. Later patches will populate the target side. For now this leaves some information redundantly recorded in both generic and type specific fields. We'll fix that in later patches. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Extend zero-recv test with methods using msghdrDavid Gibson2024-07-171-8/+52
| | | | | | | | | | | This test program verifies that we can receive and discard datagrams by using recv() with a NULL buffer and zero-length. Extend it to verify it also works using recvmsg() and either an iov with a zero-length NULL buffer or an iov that itself is NULL and zero-length. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> [sbrivio: Fixed printf() message in main of recv-zero.c] Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Test behaviour of closing duplicate UDP socketsDavid Gibson2024-07-173-2/+108
| | | | | | | | | | | | | | To simplify lifetime management of "listening" UDP sockets, UDP flow support needs to duplicate existing bound sockets. Those duplicates will be close()d when their corresponding flow expires, but we expect the original to still receive datagrams as always. That is, we expect the close() on the duplicate to remove the duplicated fd, but not to close the underlying UDP socket. Add a test program to doc/platform-requirements to verify this requirement. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp_splice: Use parameterised macros for per-side event/flag bitsDavid Gibson2024-07-172-41/+34
| | | | | | | | | | | | | | | | | | Both the events and flags fields in tcp_splice_conn have several bits which are per-side, e.g. OUT_WAIT_0 for side 0 and OUT_WAIT_1 for side 1. This necessitates some rather awkward ternary expressions when we need to get the relevant bit for a particular side. Simplify this by using a parameterised macro for the bit values. This needs a ternary expression inside the macros, but makes the places we use it substantially clearer. That simplification in turn allows us to use a loop across each side to implement several things which are currently open coded to do equivalent things for each side in turn. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow: Introduce flow_foreach_sidei() macroDavid Gibson2024-07-172-3/+9
| | | | | | | | | We have a handful of places where we use a loop to step through each side of a flow or flows, and we're probably going to have mroe in future. Introduce a macro to implement this loop for convenience. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow, tcp_splice: Prefer 'sidei' for variables referring to side indexDavid Gibson2024-07-173-62/+63
| | | | | | | | | | | | | In various places we have variables named 'side' or similar which always have the value 0 or 1 (INISIDE or TGTSIDE). Given a flow, this refers to a specific side of it. Upcoming flow table work will make it more useful for "side" to refer to a specific side of a specific flow. To make things less confusing then, prefer the name term "side index" and name 'sidei' for variables with just the 0 or 1 value. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> [sbrivio: Fixed minor detail in comment to struct flow_common] Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* flow, icmp, tcp: Clean up helpers for getting flow from indexDavid Gibson2024-07-174-17/+80
| | | | | | | | | | | | | | | | | TCP (both regular and spliced) and ICMP both have macros to retrieve the relevant protcol specific flow structure from a flow index. In most cases what we actually want is to get the specific flow from a sidx. Replace those simple macros with a more precise inline, which also asserts that the flow is of the type we expect. While we're they're also add a pif_at_sidx() helper to get the interface of a specific flow & side, which is useful in some places. Finally, fix some minor style issues in the comments on some of the existing sidx related helpers. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Handle errors on UDP socketsDavid Gibson2024-07-173-0/+92
| | | | | | | | | | | | | | | | | | Currently we ignore all events other than EPOLLIN on UDP sockets. This means that if we ever receive an EPOLLERR event, we'll enter an infinite loop on epoll, because we'll never do anything to clear the error. Luckily that doesn't seem to have happened in practice, but it's certainly fragile. Furthermore changes in how we handle UDP sockets with the flow table mean we will start receiving error events. Add handling of EPOLLERR events. For now we just read the error from the error queue (thereby clearing the error state) and print a debug message. We can add more substantial handling of specific events in future if we want to. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* util: Add AF_UNSPEC support to sockaddr_ntop()David Gibson2024-07-171-0/+4
| | | | | | | | | | | Allow sockaddr_ntop() to format AF_UNSPEC socket addresses. There do exist a few cases where we might legitimately have either an AF_UNSPEC or a real address, such as the origin address from MSG_ERRQUEUE. Even in cases where we shouldn't get an AF_UNSPEC address, formatting it is likely to make things easier to debug if we ever somehow do. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp, tcp: Tweak handling of no_udp and no_tcp flagsDavid Gibson2024-07-172-5/+22
| | | | | | | | | | | | | | | | We abort the UDP socket handler if the no_udp flag is set. But if UDP was disabled we should never have had a UDP socket to trigger the handler in the first place. If we somehow did, ignoring it here isn't really going to help because aborting without doing anything is likely to lead to an epoll loop. The same is the case for the TCP socket and timer handlers and the no_tcp flag. Change these checks on the flag to ASSERT()s. Similarly add ASSERT()s to several other entry points to the protocol specific code which should never be called if the protocol is disabled. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Make udp_sock_recv staticDavid Gibson2024-07-171-2/+2
| | | | | | | | Through an oversight this was previously declared as a public function although it's only used in udp.c and there is no prototype in any header. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* conf: Don't configure port forwarding for a disabled protocolDavid Gibson2024-07-171-0/+5
| | | | | | | | | | | | | UDP and/or TCP can be disabled with the --no-udp and --no-tcp options. However, when this is specified, it's still possible to configure forwarded ports for the disabled protocol. In some cases this will open sockets and perform other actions, which might not be safe since the entire protocol won't be initialised. Check for this case, and explicitly forbid it. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: handle shrunk window advertisements from guestJon Maloy2024-07-151-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A bug in kernel TCP may lead to a deadlock where a zero window is sent from the guest peer, while it is unable to send out window updates even after socket reads have freed up enough buffer space to permit a larger window. In this situation, new window advertisements from the peer can only be triggered by data packets arriving from this side. However, currently such packets are never sent, because the zero-window condition prevents this side from sending out any packets whatsoever to the peer. We notice that the above bug is triggered *only* after the peer has dropped one or more arriving packets because of severe memory squeeze, and that we hence always enter a retransmission situation when this occurs. This also means that the implementation goes against the RFC-9293 recommendation that a previously advertised window never should shrink. RFC-9293 seems to permit that we can continue sending up to the right edge of the last advertised non-zero window in such situations, so that is what we do to resolve this situation. It turns out that this solution is extremely simple to implememt in the code: We just omit to save the advertised zero-window when we see that it has shrunk, i.e., if the acknowledged sequence number in the advertisement message is lower than that of the last data byte sent from our side. When that is the case, the following happens: - The 'retr' flag in tcp_data_from_tap() will be 'false', so no retransmission will occur at this occasion. - The data stream will soon reach the right edge of the previously advertised window. In fact, in all observed cases we have seen that it is already there when the zero-advertisement arrives. - At that moment, the flags STALLED and ACK_FROM_TAP_DUE will be set, unless they already have been, meaning that only the next timer expiration will open for data retransmission or transmission. - When that happens, the memory squeeze at the guest will normally have abated, and the data flow can resume. It should be noted that although this solves the problem we have at hand, it is a work-around, and not a genuine solution to the described kernel bug. Suggested-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: Jon Maloy <jmaloy@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> [sbrivio: Minor fix in commit title and commit reference in comment to workaround Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* tcp: leverage support of SO_PEEK_OFF socket option when availableJon Maloy2024-07-153-9/+73
| | | | | | | | | | | | | | | | | | | | | >From linux-6.9.0 the kernel will contain commit 05ea491641d3 ("tcp: add support for SO_PEEK_OFF socket option"). This new feature makes is possible to call recv_msg(MSG_PEEK) and make it start reading data from a given offset set by the SO_PEEK_OFF socket option. This way, we can avoid repeated reading of already read bytes of a received message, hence saving read cycles when forwarding TCP messages in the host->name space direction. In this commit, we add functionality to leverage this feature when available, while we fall back to the previous behavior when not. Measurements with iperf3 shows that throughput increases with 15-20 percent in the host->namespace direction when this feature is used. Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Jon Maloy <jmaloy@redhat.com> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Trivial fix for reuseaddr-priorityDavid Gibson2024-07-151-1/+1
| | | | | | | | | | | | | This test program checks for particular behaviour regardless of order of operations. So, we step through the test with all possible orders for a number of different of parts. Or at least, we're supposed to, a copy pasta error led to using the same order for two things which should be independent. Fixes: 299c40750137 ("doc: Add program to document and test assumptions about SO_REUSEADDR") Reported-by: David Taylor <davidt@yadt.co.uk> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Test behaviour of zero length datagram recv()sDavid Gibson2024-07-053-3/+78
| | | | | | | | Add a test program verifying that we're able to discard datagrams from a socket without needing a big discard buffer, by using a zero length recv(). Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Add program to document and test assumptions about SO_REUSEADDRDavid Gibson2024-07-056-0/+417
| | | | | | | | | | | | | | For the approach we intend to use for handling UDP flows, we have some pretty specific requirements about how SO_REUSEADDR works with UDP sockets. Specifically SO_REUSEADDR allows multiple sockets with overlapping bind()s, and therefore there can be multiple sockets which are eligible to receive the same datagram. Which one will actually receive it is important to us. Add a test program which verifies things work the way we expect, which documents what those expectations are in the process. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Consolidate datagram batchingDavid Gibson2024-07-051-90/+42
| | | | | | | | | | | | | | | | | | | When we receive datagrams on a socket, we need to split them into batches depending on how they need to be forwarded (either via a specific splice socket, or via tap). The logic to do this, is somewhat awkwardly split between udp_buf_sock_handler() itself, udp_splice_send() and udp_tap_send(). Move all the batching logic into udp_buf_sock_handler(), leaving udp_splice_send() to just send the prepared batch. udp_tap_send() reduces to just a call to tap_send_frames() so open-code that call in udp_buf_sock_handler(). This will allow separating the batching logic from the rest of the datagram forwarding logic, which we'll need for upcoming flow table support. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Move some more of sock_handler tasks into sub-functionsDavid Gibson2024-07-051-46/+84
| | | | | | | | | | | | | | | | | udp_buf_sock_handler(), udp_splice_send() and udp_tap_send loosely, do four things between them: 1. Receive some datagrams from a socket 2. Split those datagrams into batches depending on how they need to be sent (via tap or via a specific splice socket) 3. Prepare buffers for each datagram to send it onwards 4. Actually send it onwards Split (1) and (3) into specific helper functions. This isn't immediately useful (udp_splice_prepare(), in particular, is trivial), but it will make further reworks clearer. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Don't repeatedly initialise udp[46]_eth_hdrDavid Gibson2024-07-051-2/+3
| | | | | | | | | | | | Since we split our packet frame buffers into different pieces, we have a single buffer per IP version for the ethernet header, rather than one per frame. This makes sense since our ethernet header is alwaus the same. However we initialise those buffers udp[46]_eth_hdr inside a per frame loop. Pull that outside the loop so we just initialise them once. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* udp: Unify udp[46]_l2_iovDavid Gibson2024-07-051-23/+19
| | | | | | | | | | | | | | The only differences between these arrays are that udp4_l2_iov is pre-initialised to point to the IPv4 ethernet header, and IPv4 per-frame header and udp6_l2_iov points to the IPv6 versions. We already have to set up a bunch of headers per-frame, including updating udp[46]_l2_iov[i][UDP_IOV_PAYLOAD].iov_len. It makes more sense to adjust the IOV entries to point at the correct headers for the frame than to have two complete sets of iovecs. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
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