Don't proxy middleware if host is the same

[ascorbic]

This changes the check for whether a rewrite is internal or if it should be proxied. Currently it checks if protocol is unset, which is only the case for relative URLs or localhost. This means that requests where there is a hostname set, or if localhost is specified in another way such as 127.0.0.1, then it will be proxied, which potentially causes a proxy loop or ssl error. This PR changes the test so that it also checks if the hosts match, and only proxies if they are different.

Fixes #31179

Bug

• Related issues linked using fixes #number
• Integration tests added
• Errors have helpful link attached, see contributing.md

[ascorbic]

Thanks for approving @Kikobeats. Is there anythimng blocking this being merged?

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
buildDuration	23.6s	24.3s	⚠️ +775ms
buildDurationCached	4.7s	4.7s	-16ms
nodeModulesSize	335 MB	335 MB	⚠️ +276 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
/ failed reqs	0	0	✓
/ total time (seconds)	4.061	4.091	⚠️ +0.03
/ avg req/sec	615.69	611.16	⚠️ -4.53
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.071	2.126	⚠️ +0.05
/error-in-render avg req/sec	1206.88	1175.97	⚠️ -30.91

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	28.3 kB	28.3 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.2 kB	72.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
_app-HASH.js gzip	1.37 kB	1.37 kB	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	2.38 kB	2.38 kB	✓
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	635 B	635 B	✓
image-HASH.js gzip	4.44 kB	4.44 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	1.87 kB	1.87 kB	✓
routerDirect..HASH.js gzip	321 B	321 B	✓
script-HASH.js gzip	383 B	383 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	13.3 kB	13.3 kB	✓

Client Build Manifests

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
_buildManifest.js gzip	460 B	460 B	✓
Overall change	460 B	460 B	✓

Rendered Page Sizes

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
index.html gzip	524 B	524 B	✓
link.html gzip	535 B	535 B	✓
withRouter.html gzip	517 B	517 B	✓
Overall change	1.58 kB	1.58 kB	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
buildDuration	26.4s	25.5s	-874ms
buildDurationCached	4.8s	4.6s	-152ms
nodeModulesSize	335 MB	335 MB	⚠️ +276 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
/ failed reqs	0	0	✓
/ total time (seconds)	4.192	4.059	-0.13
/ avg req/sec	596.41	615.87	+19.46
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.179	2.197	⚠️ +0.02
/error-in-render avg req/sec	1147.34	1137.86	⚠️ -9.48

Client Bundles (main, webpack, commons)

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.5 kB	28.5 kB	✓
webpack-HASH.js gzip	1.43 kB	1.43 kB	✓
Overall change	72.5 kB	72.5 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	305 B	305 B	✓
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.38 kB	2.38 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	622 B	622 B	✓
image-HASH.js gzip	4.46 kB	4.46 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	1.91 kB	1.91 kB	✓
routerDirect..HASH.js gzip	314 B	314 B	✓
script-HASH.js gzip	375 B	375 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	13.2 kB	13.2 kB	✓

Client Build Manifests

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	ascorbic/next.js mk/proxy-host	Change
index.html gzip	521 B	521 B	✓
link.html gzip	533 B	533 B	✓
withRouter.html gzip	515 B	515 B	✓
Overall change	1.57 kB	1.57 kB	✓

Commit: 0ab1d04