terraform-course/demo-16/securitygroup.tf

resource "aws_security_group" "myinstance" {
  vpc_id = "${aws_vpc.main.id}"
  name = "myinstance"
  description = "security group for my instance"
  egress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      cidr_blocks = ["0.0.0.0/0"]
  }

  ingress {
      from_port = 22
      to_port = 22
      protocol = "tcp"
      cidr_blocks = ["0.0.0.0/0"]
  } 

  ingress {
      from_port = 80
      to_port = 80
      protocol = "tcp"
      security_groups = ["${aws_security_group.elb-securitygroup.id}"]
  }

  tags {
    Name = "myinstance"
  }
}
resource "aws_security_group" "elb-securitygroup" {
  vpc_id = "${aws_vpc.main.id}"
  name = "elb"
  description = "security group for load balancer"
  egress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      cidr_blocks = ["0.0.0.0/0"]
  }

  ingress {
      from_port = 80
      to_port = 80
      protocol = "tcp"
      cidr_blocks = ["0.0.0.0/0"]
  } 
  tags {
    Name = "elb"
  }
}