Attachment 18260 Details for Bug 15536 – patch adding minimal EDNS0 support

[patch] patch adding minimal EDNS0 support

edns0.diff (text/plain), 1.82 KB, created by Michael Tokarev on 2024-02-26 11:22:12 UTC

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Creator: Michael Tokarev

Created: 2024-02-26 11:22:12 UTC

Size: 1.82 KB

patch

obsolete

>From: Michael Tokarev <mjt@tls.msk.ru>
>Subject: Minimal EDNS0 support for built-in DNS client
>Date: Mon, 26 Feb 2024 14:15:00 +0300
>
>Currently, samba built-in DNS client is UDP-only (it does
>support TCP mode, but not all components use it).  In
>particular, when winbind queries list of AD DCs (SRV
>record) which can be quite large, it uses UDP-only query.
>And at the same time, samba DNS client does not support
>EDNS0 at all, so the reply is limited to standard DNS
>packet size which is 512 bytes.
>
>Add minimal EDNS0 OPT record to ADDITIONAL section when
>sending a DNS request out, indicating we can accept
>DNS packets up to 4Kb in size.
>
>Since DNSSEC is in wide use today and DNSSEC requires
>EDNS0, it is okay to assume ENDS0 is widely supported
>these days, so there should be no regressions when
>enabling EDNS0.
>
>Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
>
>diff --git a/libcli/dns/dns.c b/libcli/dns/dns.c
>index 943b4d5b33e..81144601bb8 100644
>--- a/libcli/dns/dns.c
>+++ b/libcli/dns/dns.c
>@@ -422,6 +422,7 @@ struct tevent_req *dns_cli_request_send(TALLOC_CTX *mem_ctx,
> 	struct dns_cli_request_state *state;
> 	struct dns_name_question question;
> 	struct dns_name_packet out_packet;
>+	struct dns_res_rec edns0_opt;
> 	enum ndr_err_code ndr_err;
> 
> 	req = tevent_req_create(mem_ctx, &state,
>@@ -443,11 +444,19 @@ struct tevent_req *dns_cli_request_send(TALLOC_CTX *mem_ctx,
> 		.question_type = qtype, .question_class = qclass
> 	};
> 
>+	edns0_opt = (struct dns_res_rec) {
>+		.name = "",
>+		.rr_type = DNS_QTYPE_OPT,
>+		.rr_class = 4096 /* 4096 bytes UDP buffer size */
>+	};
>+
> 	out_packet = (struct dns_name_packet) {
> 		.id = state->req_id,
> 		.operation = DNS_OPCODE_QUERY | DNS_FLAG_RECURSION_DESIRED,
> 		.qdcount = 1,
>-		.questions = &question
>+		.questions = &question,
>+		.arcount = 1,
>+		.additional = &edns0_opt
> 	};
> 
> 	ndr_err = ndr_push_struct_blob(

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Attachments on bug 15536: 18260