feat(connect): add --server-name flag for tunneled connections by jimmystridh · Pull Request #678 · microsoft/go-sqlcmd

jimmystridh · 2026-01-29T23:11:03Z

Problem

When connecting to Azure SQL through an SSH tunnel or proxy (e.g., 127.0.0.1:11433), connections fail because SQL Server validates the hostname in the TDS LOGIN7 packet. The server receives 127.0.0.1 as the server name and rejects it with "Cannot open server '127.0.0.1' requested by the login".

Current workaround requires adding /etc/hosts entries mapping the real server name to 127.0.0.1.

Fixes #576

Solution

Add a --server-name flag that specifies the server name to send in the login packet, separate from the dial address (-S).

# Connect via tunnel on localhost:11433, authenticate as the real server
sqlcmd -S 127.0.0.1,11433 --server-name myserver.database.windows.net \
    -U myuser -P mypass -N -C

Implementation

Add ServerNameOverride field to ConnectSettings
Build the connection string using the override host/instance (so LOGIN7 uses the override)
Use a proxy dialer that rewrites the network dial target back to the original -S host/port
Skip override for named pipes

Allows specifying the server name sent in the TDS LOGIN7 packet separately from the dial address. Fixes connections through SSH tunnels or proxies to Azure SQL where the server validates hostname. Refs: microsoft#576

jimmystridh · 2026-01-29T23:13:23Z

@microsoft-github-policy-service agree

Copilot

Pull request overview

Adds support for overriding the server name used during TDS login (and related connection metadata) so sqlcmd can connect through tunnels/proxies (e.g., 127.0.0.1:11433) while authenticating as the real Azure SQL hostname.

Changes:

Introduces ConnectSettings.ServerNameOverride and applies it when building the connection string.
Adds a proxyDialer to rewrite the actual dial target while keeping the overridden server name for login.
Adds unit tests covering the new connection string behavior and dialer behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pkg/sqlcmd/connect.go	Adds `ServerNameOverride` and applies it during connection string construction.
pkg/sqlcmd/sqlcmd.go	Attempts to attach a custom dialer when `ServerNameOverride` is set.
pkg/sqlcmd/dialer.go	Implements a dialer that rewrites dial host/port while reporting an overridden hostname.
pkg/sqlcmd/dialer_test.go	Adds unit tests for `proxyDialer`.
pkg/sqlcmd/sqlcmd_test.go	Extends connection string tests to cover `ServerNameOverride`.

pkg/sqlcmd/sqlcmd.go

pkg/sqlcmd/connect.go

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

pkg/sqlcmd/connect.go

pkg/sqlcmd/sqlcmd.go

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

pkg/sqlcmd/sqlcmd.go

pkg/sqlcmd/dialer.go

pkg/sqlcmd/connect.go

jimmystridh · 2026-02-03T22:58:57Z

Addressed the remaining review notes:

If --server-name is set but the connector isn’t *mssql.Connector, we now return an explicit error instead of silently changing the DSN host (commit c6f6ec4).
proxyDialer now embeds a zero-value net.Dialer to avoid a race on lazy init (commit c6f6ec4).
Added a named-pipe override test to ensure ServerNameOverride is ignored for np connections (commit c6f6ec4).
The --server-name flag wiring is included in cmd/sqlcmd/sqlcmd.go in the same commit.

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

pkg/sqlcmd/sqlcmd.go

cmd/sqlcmd/sqlcmd.go

shueybubbles · 2026-02-03T23:19:59Z

pkg/sqlcmd/sqlcmd.go

+					targetPort: targetPort,
+				}
+			} else {
+				return localizer.Errorf("Server name override is not supported with the current authentication method")


localizer.Errorf(

run build\build to generate localization files with the new strings

or maybe just go generate but I'm not sure

feat(connect): add --server-name flag for tunneled connections

611d165

Allows specifying the server name sent in the TDS LOGIN7 packet separately from the dial address. Fixes connections through SSH tunnels or proxies to Azure SQL where the server validates hostname. Refs: microsoft#576

dlevy-msft-sql requested a review from Copilot January 30, 2026 01:03

Copilot started reviewing on behalf of dlevy-msft-sql January 30, 2026 01:03 View session

Merge branch 'main' into feature/server-name-override

7915010

dlevy-msft-sql added enhancement New feature or request Size: S Small issue (less than one week effort) labels Jan 30, 2026

Copilot AI reviewed Jan 30, 2026

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Fix connector typing for server-name override

eb57f2a

dlevy-msft-sql assigned jimmystridh and dlevy-msft-sql Jan 30, 2026

dlevy-msft-sql requested a review from Copilot January 30, 2026 17:02

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Normalize server-name override for dialer

d3a58c7

dlevy-msft-sql requested a review from Copilot January 31, 2026 19:41

Copilot started reviewing on behalf of dlevy-msft-sql January 31, 2026 19:41 View session

dlevy-msft-sql added the connectivity label Jan 31, 2026

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Handle server-name override edge cases

c6f6ec4

dlevy-msft-sql requested a review from Copilot February 3, 2026 23:00

Copilot started reviewing on behalf of dlevy-msft-sql February 3, 2026 23:00 View session

Merge branch 'main' into feature/server-name-override

b25775a

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feat(connect): add --server-name flag for tunneled connections#678

feat(connect): add --server-name flag for tunneled connections#678
jimmystridh wants to merge 6 commits intomicrosoft:mainfrom
jimmystridh:feature/server-name-override

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jimmystridh commented Jan 29, 2026 •

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