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| 1 | +package routeutils |
| 2 | + |
| 3 | +import ( |
| 4 | + "fmt" |
| 5 | + elbv2model "sigs.k8s.io/aws-load-balancer-controller/pkg/model/elbv2" |
| 6 | + gwv1 "sigs.k8s.io/gateway-api/apis/v1" |
| 7 | + "strings" |
| 8 | +) |
| 9 | + |
| 10 | +const ( |
| 11 | + replaceWholeHostHeaderRegex = ".*" |
| 12 | + replaceWholePathMinusQueryParamsRegex = "^([^?]*)" |
| 13 | +) |
| 14 | + |
| 15 | +func BuildRoutingRuleTransforms(gwRoute RouteDescriptor, gwRule RulePrecedence) []elbv2model.Transform { |
| 16 | + switch gwRoute.GetRouteKind() { |
| 17 | + case HTTPRouteKind: |
| 18 | + return buildHTTPRuleTransforms(gwRule.CommonRulePrecedence.Rule.GetRawRouteRule().(*gwv1.HTTPRouteRule), gwRule.HTTPMatch) |
| 19 | + default: |
| 20 | + return []elbv2model.Transform{} |
| 21 | + } |
| 22 | +} |
| 23 | + |
| 24 | +func buildHTTPRuleTransforms(rule *gwv1.HTTPRouteRule, httpMatch *gwv1.HTTPRouteMatch) []elbv2model.Transform { |
| 25 | + var transforms []elbv2model.Transform |
| 26 | + |
| 27 | + if rule != nil { |
| 28 | + for _, rf := range rule.Filters { |
| 29 | + if rf.URLRewrite != nil { |
| 30 | + if rf.URLRewrite.Path != nil { |
| 31 | + transforms = append(transforms, generateURLRewritePathTransform(*rf.URLRewrite.Path, httpMatch)) |
| 32 | + } |
| 33 | + |
| 34 | + if rf.URLRewrite.Hostname != nil { |
| 35 | + transforms = append(transforms, generateHostHeaderRewriteTransform(*rf.URLRewrite.Hostname)) |
| 36 | + } |
| 37 | + } |
| 38 | + } |
| 39 | + } |
| 40 | + |
| 41 | + return transforms |
| 42 | +} |
| 43 | + |
| 44 | +func generateHostHeaderRewriteTransform(hostname gwv1.PreciseHostname) elbv2model.Transform { |
| 45 | + return elbv2model.Transform{ |
| 46 | + Type: elbv2model.TransformTypeHostHeaderRewrite, |
| 47 | + HostHeaderRewriteConfig: &elbv2model.RewriteConfigObject{ |
| 48 | + Rewrites: []elbv2model.RewriteConfig{ |
| 49 | + { |
| 50 | + Regex: replaceWholeHostHeaderRegex, |
| 51 | + Replace: string(hostname), |
| 52 | + }, |
| 53 | + }, |
| 54 | + }, |
| 55 | + } |
| 56 | +} |
| 57 | + |
| 58 | +func generateURLRewritePathTransform(gwPathModifier gwv1.HTTPPathModifier, httpMatch *gwv1.HTTPRouteMatch) elbv2model.Transform { |
| 59 | + var replacementRegex string |
| 60 | + var replacement string |
| 61 | + |
| 62 | + switch gwPathModifier.Type { |
| 63 | + case gwv1.FullPathHTTPPathModifier: |
| 64 | + // Capture just the path, not the query parameters |
| 65 | + replacementRegex = replaceWholePathMinusQueryParamsRegex |
| 66 | + replacement = *gwPathModifier.ReplaceFullPath |
| 67 | + break |
| 68 | + case gwv1.PrefixMatchHTTPPathModifier: |
| 69 | + replacementRegex, replacement = generatePrefixReplacementRegex(httpMatch, *gwPathModifier.ReplacePrefixMatch) |
| 70 | + break |
| 71 | + default: |
| 72 | + // Need to set route status as failed :blah: |
| 73 | + // Probably do this in the routeutils loader step and for validation. |
| 74 | + } |
| 75 | + return elbv2model.Transform{ |
| 76 | + Type: elbv2model.TransformTypeUrlRewrite, |
| 77 | + UrlRewriteConfig: &elbv2model.RewriteConfigObject{ |
| 78 | + Rewrites: []elbv2model.RewriteConfig{ |
| 79 | + { |
| 80 | + Regex: replacementRegex, |
| 81 | + Replace: replacement, |
| 82 | + }, |
| 83 | + }, |
| 84 | + }, |
| 85 | + } |
| 86 | +} |
| 87 | + |
| 88 | +func generatePrefixReplacementRegex(httpMatch *gwv1.HTTPRouteMatch, replacement string) (string, string) { |
| 89 | + match := *httpMatch.Path.Value |
| 90 | + |
| 91 | + /* |
| 92 | + If we're being asked to replace a prefix with "", we still need to keep one '/' to form a valid path. |
| 93 | + Consider getting the path '/foo' and having the replacement string being '', we would transform '/foo' => '' |
| 94 | + thereby leaving an invalid path of ''. We could (in theory) do this for all replacements, e.g. replace = 'cat' |
| 95 | + we could transform this into '/cat' here, but tbh the user can also do this, and I'm not entirely |
| 96 | + sure if we could handle all possible cases. |
| 97 | +
|
| 98 | + To explain the addition of $2, we set up an optional capture group after the initial prefix match. We only want |
| 99 | + to add back the value of the optional capture group when the replacement doesn't already have a '/' suffix. |
| 100 | + A couple examples: |
| 101 | +
|
| 102 | + Without the capture group, e.g. (^%s) |
| 103 | + input path = '/foo/', prefixRegex = '(^/foo)', replacement value = '/cat/' results in '/cat//' |
| 104 | +
|
| 105 | + To extend the example, now consider using having the capture group and always adding that to the result. |
| 106 | + input path = '/foo/', prefixRegex = '(^/foo(/)?)', replacement value = '/cat/$2' results in (again) '/cat//' |
| 107 | +
|
| 108 | + Without the capture group, we would have one '/' too few. |
| 109 | + input path = '/foo/bar', prefixRegex = '(^/foo(/)?)', replacement value = '/cat$2' results in '/catbar' |
| 110 | +
|
| 111 | + */ |
| 112 | + if replacement == "" { |
| 113 | + replacement = "/" |
| 114 | + } else if !strings.HasSuffix(replacement, "/") { |
| 115 | + replacement = fmt.Sprintf("%s$2", replacement) |
| 116 | + } |
| 117 | + |
| 118 | + return fmt.Sprintf("(^%s(/)?)", match), replacement |
| 119 | +} |
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