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Diffstat (limited to 'modules/edns_keepalive')
| -rw-r--r-- | modules/edns_keepalive/README.rst | 12 | ||||
| -rw-r--r-- | modules/edns_keepalive/edns_keepalive.c | 77 | ||||
| -rw-r--r-- | modules/edns_keepalive/edns_keepalive.mk | 5 |
3 files changed, 94 insertions, 0 deletions
diff --git a/modules/edns_keepalive/README.rst b/modules/edns_keepalive/README.rst new file mode 100644 index 0000000..7938632 --- /dev/null +++ b/modules/edns_keepalive/README.rst @@ -0,0 +1,12 @@ +.. _mod-edns_keepalive: + +EDNS keepalive +-------------- + +The ``edns_keepalive`` module implements :rfc:`7828` for *clients* connecting to Knot Resolver via TCP and TLS. +Note that client connections are timed-out the same way *regardless* of them sending the EDNS option; +the module just allows clients to discover the timeout. + +When connecting to servers, Knot Resolver does not send this EDNS option. +It still attempts to reuse established connections intelligently. + diff --git a/modules/edns_keepalive/edns_keepalive.c b/modules/edns_keepalive/edns_keepalive.c new file mode 100644 index 0000000..99c0d96 --- /dev/null +++ b/modules/edns_keepalive/edns_keepalive.c @@ -0,0 +1,77 @@ +/* Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz> + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. + */ + +/** + * @file edns_keepalive.c + * @brief Minimalistic EDNS keepalive implementation on server side. + * If keepalive option is present in query, + * always reply with constant timeout value. + * + */ +#include <libknot/packet/pkt.h> +#include "daemon/worker.h" +#include "lib/module.h" +#include "lib/layer.h" + +static int edns_keepalive_finalize(kr_layer_t *ctx) +{ + struct kr_request *req = ctx->req; + knot_pkt_t *answer = req->answer; + const knot_rrset_t *src_opt = req->qsource.packet->opt_rr; + knot_rrset_t *answ_opt = answer->opt_rr; + + const bool ka_want = + req->qsource.flags.tcp && + src_opt != NULL && + knot_edns_get_option(src_opt, KNOT_EDNS_OPTION_TCP_KEEPALIVE) && + answ_opt != NULL; + if (!ka_want) { + return ctx->state; + } + const struct worker_ctx *worker = (const struct worker_ctx *)req->daemon_context; + assert(worker); + const struct network *net = &worker->engine->net; + uint64_t timeout = net->tcp.in_idle_timeout / 100; + if (timeout > UINT16_MAX) { + timeout = UINT16_MAX; + } + knot_mm_t *pool = &answer->mm; + uint16_t ka_size = knot_edns_keepalive_size(timeout); + uint8_t ka_buf[ka_size]; + int ret = knot_edns_keepalive_write(ka_buf, ka_size, timeout); + if (ret == KNOT_EOK) { + ret = knot_edns_add_option(answ_opt, KNOT_EDNS_OPTION_TCP_KEEPALIVE, + ka_size, ka_buf, pool); + } + if (ret != KNOT_EOK) { + ctx->state = KR_STATE_FAIL; + } + return ctx->state; +} + +KR_EXPORT +const kr_layer_api_t *edns_keepalive_layer(struct kr_module *module) +{ + static kr_layer_api_t _layer = { + .answer_finalize = &edns_keepalive_finalize, + }; + /* Store module reference */ + _layer.data = module; + return &_layer; +} + +KR_MODULE_EXPORT(edns_keepalive) + diff --git a/modules/edns_keepalive/edns_keepalive.mk b/modules/edns_keepalive/edns_keepalive.mk new file mode 100644 index 0000000..4ce2bd9 --- /dev/null +++ b/modules/edns_keepalive/edns_keepalive.mk @@ -0,0 +1,5 @@ +edns_keepalive_CFLAGS := -fPIC +edns_keepalive_LDFLAGS := -Wl,-undefined -Wl,dynamic_lookup +edns_keepalive_SOURCES := modules/edns_keepalive/edns_keepalive.c +$(call make_c_module,edns_keepalive) + |