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b9b72cb3ce
A client that opens a socket but does not negotiate is merely hogging
qemu's resources (an open fd and a small amount of memory); and a
malicious client that can access the port where NBD is listening can
attempt a denial of service attack by intentionally opening and
abandoning lots of unfinished connections. The previous patch put a
default bound on the number of such ongoing connections, but once that
limit is hit, no more clients can connect (including legitimate ones).
The solution is to insist that clients complete handshake within a
reasonable time limit, defaulting to 10 seconds. A client that has
not successfully completed NBD_OPT_GO by then (including the case of
where the client didn't know TLS credentials to even reach the point
of NBD_OPT_GO) is wasting our time and does not deserve to stay
connected. Later patches will allow fine-tuning the limit away from
the default value (including disabling it for doing integration
testing of the handshake process itself).
Note that this patch in isolation actually makes it more likely to see
qemu SEGV after nbd-server-stop, as any client socket still connected
when the server shuts down will now be closed after 10 seconds rather
than at the client's whims. That will be addressed in the next patch.
For a demo of this patch in action:
$ qemu-nbd -f raw -r -t -e 10 file &
$ nbdsh --opt-mode -c '
H = list()
for i in range(20):
print(i)
H.insert(i, nbd.NBD())
H[i].set_opt_mode(True)
H[i].connect_uri("nbd://localhost")
'
$ kill $!
where later connections get to start progressing once earlier ones are
forcefully dropped for taking too long, rather than hanging.
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240807174943.771624-13-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
[eblake: rebase to changes earlier in series, reduce scope of timer]
Signed-off-by: Eric Blake <eblake@redhat.com>
83 lines
7.9 KiB
Plaintext
83 lines
7.9 KiB
Plaintext
# See docs/devel/tracing.rst for syntax documentation.
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# client.c
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nbd_send_option_request(uint32_t opt, const char *name, uint32_t len) "Sending option request %" PRIu32" (%s), len %" PRIu32
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nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t type, const char *typename, uint32_t length) "Received option reply %" PRIu32" (%s), type %" PRIu32" (%s), len %" PRIu32
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nbd_server_error_msg(uint32_t err, const char *type, const char *msg) "server reported error 0x%" PRIx32 " (%s) with additional message: %s"
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nbd_reply_err_ignored(uint32_t option, const char *name, uint32_t reply, const char *reply_name) "server failed request %" PRIu32 " (%s) with error 0x%" PRIx32 " (%s), attempting fallback"
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nbd_receive_list(const char *name, const char *desc) "export list includes '%s', description '%s'"
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nbd_opt_info_go_start(const char *opt, const char *name) "Attempting %s for export '%s'"
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nbd_opt_info_go_success(const char *opt) "Export is ready after %s request"
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nbd_opt_info_unknown(int info, const char *name) "Ignoring unknown info %d (%s)"
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nbd_opt_info_block_size(uint32_t minimum, uint32_t preferred, uint32_t maximum) "Block sizes are 0x%" PRIx32 ", 0x%" PRIx32 ", 0x%" PRIx32
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nbd_receive_query_exports_start(const char *wantname) "Querying export list for '%s'"
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nbd_receive_query_exports_success(const char *wantname) "Found desired export name '%s'"
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nbd_receive_starttls_new_client(void) "Setting up TLS"
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nbd_receive_starttls_tls_handshake(void) "Starting TLS handshake"
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nbd_opt_meta_request(const char *optname, const char *context, const char *export) "Requesting %s %s for export %s"
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nbd_opt_meta_reply(const char *optname, const char *context, uint32_t id) "Received %s mapping of %s to id %" PRIu32
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nbd_start_negotiate(void *tlscreds, const char *hostname) "Receiving negotiation tlscreds=%p hostname=%s"
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nbd_receive_negotiate_magic(uint64_t magic) "Magic is 0x%" PRIx64
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nbd_receive_negotiate_server_flags(uint32_t globalflags) "Global flags are 0x%" PRIx32
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nbd_receive_negotiate_name(const char *name) "Requesting NBD export name '%s'"
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nbd_receive_negotiate_size_flags(uint64_t size, uint16_t flags) "Size is %" PRIu64 ", export flags 0x%" PRIx16
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nbd_init_set_socket(void) "Setting NBD socket"
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nbd_init_set_block_size(unsigned long block_size) "Setting block size to %lu"
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nbd_init_set_size(unsigned long sectors) "Setting size to %lu block(s)"
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nbd_init_trailing_bytes(int ignored_bytes) "Ignoring trailing %d bytes of export"
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nbd_init_set_readonly(void) "Setting readonly attribute"
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nbd_init_finish(void) "Negotiation ended"
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nbd_client_loop(void) "Doing NBD loop"
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nbd_client_loop_ret(int ret, const char *error) "NBD loop returned %d: %s"
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nbd_client_clear_queue(void) "Clearing NBD queue"
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nbd_client_clear_socket(void) "Clearing NBD socket"
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nbd_send_request(uint64_t from, uint64_t len, uint64_t cookie, uint16_t flags, uint16_t type, const char *name) "Sending request to server: { .from = %" PRIu64", .len = %" PRIu64 ", .cookie = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) }"
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nbd_receive_simple_reply(int32_t error, const char *errname, uint64_t cookie) "Got simple reply: { .error = %" PRId32 " (%s), cookie = %" PRIu64" }"
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nbd_receive_reply_chunk_header(uint16_t flags, uint16_t type, const char *name, uint64_t cookie, uint32_t length) "Got reply chunk header: { flags = 0x%" PRIx16 ", type = %" PRIu16 " (%s), cookie = %" PRIu64 ", length = %" PRIu32 " }"
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nbd_receive_wrong_header(uint32_t magic, const char *mode) "Server sent unexpected magic 0x%" PRIx32 " for negotiated mode %s"
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# common.c
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nbd_unknown_error(int err) "Squashing unexpected error %d to EINVAL"
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# server.c
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nbd_negotiate_send_rep_len(uint32_t opt, const char *optname, uint32_t type, const char *typename, uint32_t len) "Reply opt=%" PRIu32 " (%s), type=%" PRIu32 " (%s), len=%" PRIu32
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nbd_negotiate_send_rep_err(const char *msg) "sending error message \"%s\""
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nbd_negotiate_send_rep_list(const char *name, const char *desc) "Advertising export name '%s' description '%s'"
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nbd_negotiate_handle_export_name(void) "Checking length"
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nbd_negotiate_handle_export_name_request(const char *name) "Client requested export '%s'"
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nbd_negotiate_send_info(int info, const char *name, uint32_t length) "Sending NBD_REP_INFO type %d (%s) with remaining length %" PRIu32
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nbd_negotiate_handle_info_requests(int requests) "Client requested %d items of info"
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nbd_negotiate_handle_info_request(int request, const char *name) "Client requested info %d (%s)"
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nbd_negotiate_handle_info_block_size(uint32_t minimum, uint32_t preferred, uint32_t maximum) "advertising minimum 0x%" PRIx32 ", preferred 0x%" PRIx32 ", maximum 0x%" PRIx32
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nbd_negotiate_handle_starttls(void) "Setting up TLS"
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nbd_negotiate_handle_starttls_handshake(void) "Starting TLS handshake"
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nbd_negotiate_meta_context(const char *optname, const char *export, uint32_t queries) "Client requested %s for export %s, with %" PRIu32 " queries"
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nbd_negotiate_meta_query_skip(const char *reason) "Skipping meta query: %s"
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nbd_negotiate_meta_query_parse(const char *query) "Parsed meta query '%s'"
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nbd_negotiate_meta_query_reply(const char *context, uint32_t id) "Replying with meta context '%s' id %" PRIu32
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nbd_negotiate_options_flags(uint32_t flags) "Received client flags 0x%" PRIx32
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nbd_negotiate_options_check_magic(uint64_t magic) "Checking opts magic 0x%" PRIx64
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nbd_negotiate_options_check_option(uint32_t option, const char *name) "Checking option %" PRIu32 " (%s)"
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nbd_negotiate_begin(void) "Beginning negotiation"
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nbd_negotiate_new_style_size_flags(uint64_t size, unsigned flags) "advertising size %" PRIu64 " and flags 0x%x"
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nbd_negotiate_success(void) "Negotiation succeeded"
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nbd_receive_request(uint32_t magic, uint16_t flags, uint16_t type, uint64_t from, uint64_t len) "Got request: { magic = 0x%" PRIx32 ", .flags = 0x%" PRIx16 ", .type = 0x%" PRIx16 ", from = %" PRIu64 ", len = %" PRIu64 " }"
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nbd_blk_aio_attached(const char *name, void *ctx) "Export %s: Attaching clients to AIO context %p"
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nbd_blk_aio_detach(const char *name, void *ctx) "Export %s: Detaching clients from AIO context %p"
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nbd_co_send_simple_reply(uint64_t cookie, uint32_t error, const char *errname, uint64_t len) "Send simple reply: cookie = %" PRIu64 ", error = %" PRIu32 " (%s), len = %" PRIu64
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nbd_co_send_chunk_done(uint64_t cookie) "Send structured reply done: cookie = %" PRIu64
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nbd_co_send_chunk_read(uint64_t cookie, uint64_t offset, void *data, uint64_t size) "Send structured read data reply: cookie = %" PRIu64 ", offset = %" PRIu64 ", data = %p, len = %" PRIu64
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nbd_co_send_chunk_read_hole(uint64_t cookie, uint64_t offset, uint64_t size) "Send structured read hole reply: cookie = %" PRIu64 ", offset = %" PRIu64 ", len = %" PRIu64
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nbd_co_send_extents(uint64_t cookie, unsigned int extents, uint32_t id, uint64_t length, int last) "Send block status reply: cookie = %" PRIu64 ", extents = %u, context = %d (extents cover %" PRIu64 " bytes, last chunk = %d)"
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nbd_co_send_chunk_error(uint64_t cookie, int err, const char *errname, const char *msg) "Send structured error reply: cookie = %" PRIu64 ", error = %d (%s), msg = '%s'"
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nbd_co_receive_block_status_payload_compliance(uint64_t from, uint64_t len) "client sent unusable block status payload: from=0x%" PRIx64 ", len=0x%" PRIx64
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nbd_co_receive_request_decode_type(uint64_t cookie, uint16_t type, const char *name) "Decoding type: cookie = %" PRIu64 ", type = %" PRIu16 " (%s)"
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nbd_co_receive_request_payload_received(uint64_t cookie, uint64_t len) "Payload received: cookie = %" PRIu64 ", len = %" PRIu64
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nbd_co_receive_ext_payload_compliance(uint64_t from, uint64_t len) "client sent non-compliant write without payload flag: from=0x%" PRIx64 ", len=0x%" PRIx64
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nbd_co_receive_align_compliance(const char *op, uint64_t from, uint64_t len, uint32_t align) "client sent non-compliant unaligned %s request: from=0x%" PRIx64 ", len=0x%" PRIx64 ", align=0x%" PRIx32
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nbd_trip(void) "Reading request"
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nbd_handshake_timer_cb(void) "client took too long to negotiate"
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# client-connection.c
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nbd_connect_thread_sleep(uint64_t timeout) "timeout %" PRIu64
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