Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment()) {
    app.UseSwagger();
    app.UseSwaggerUI();
}

// app.UseHttpsRedirection();

app.MapGet("/", (HttpRequest request) => {

    var data = new {
        Ipv4Address = request.HttpContext.Connection.RemoteIpAddress?.MapToIPv4()?.ToString(),
        ForwardFor = request.Headers["X-Forwarded-For"],
        ForwardProto = request.Headers["X-Forwarded-Proto"],
        ForwardHost = request.Headers["X-Forwarded-Host"]
    };

    return data;
})
.WithName("Echo");

app.Run();

public class EchoData {
    public string? IPv4Address { get; set; }
}