Method extractIPsFromHeader

req.go:573–629

extractIPsFromHeader will return a slice of IPs it found given a header name in the order they appear. When IP validation is enabled, any invalid IPs will be omitted.

(header string)

// extractIPsFromHeader will return a slice of IPs it found given a header name in the order they appear.
// When IP validation is enabled, any invalid IPs will be omitted.
func (r *DefaultReq) extractIPsFromHeader(header string) []string {
	// TODO: Reuse the c.extractIPFromHeader func somehow in here

	headerValue := r.Get(header)

	// We can't know how many IPs we will return, but we will try to guess with this constant division.
	// Counting ',' makes function slower for about 50ns in general case.
	const maxEstimatedCount = 8
	estimatedCount := min(len(headerValue)/maxEstimatedCount,
		// Avoid big allocation on big header
		maxEstimatedCount)

	ipsFound := make([]string, 0, estimatedCount)

	i := 0
	j := -1

	for {
		var v4, v6 bool

		// Manually splitting string without allocating slice, working with parts directly
		i, j = j+1, j+2

		if j > len(headerValue) {
			break
		}

		for j < len(headerValue) && headerValue[j] != ',' {
			switch headerValue[j] {
			case ':':
				v6 = true
			case '.':
				v4 = true
			default:
				// do nothing
			}
			j++
		}

		for i < j && (headerValue[i] == ' ' || headerValue[i] == ',') {
			i++
		}

		s := utils.TrimRight(headerValue[i:j], ' ')

		if r.c.app.config.EnableIPValidation {
			// Skip validation if IP is clearly not IPv4/IPv6; otherwise, validate without allocations
			if (!v6 && !v4) || (v6 && !utils.IsIPv6(s)) || (v4 && !utils.IsIPv4(s)) {
				continue
			}
		}

		ipsFound = append(ipsFound, s)
	}

	return ipsFound
}