Apparatus, system, and method for applying firewall rules at dynamic offsets within packets in kernel space

A physical routing engine of a network device comprising:

• a tunnel driver, stored in kernel space, that:
• receives a packet in kernel space;
• identifies metadata of the packet that indicates whether at least one firewall filter had already been correctly applied to the packet before the packet arrived at the tunnel driver, wherein the metadata of the packet comprises an Internet Protocol (IP) header of the packet;
• determines that the IP header of the packet is offset beyond a certain threshold;
• determines, based at least in part on the IP header of the packet being offset beyond the certain threshold, that the firewall filter had not been correctly applied to the packet before the packet arrived at the tunnel driver;
• and
• in response to determining that the firewall filter had not been correctly applied to the packet, invokes at least one firewall filter hook that applies at least one firewall rule on the packet in kernel space on the physical routing engine before the packet is allowed to exit kernel space on the physical routing engine;
• and
• at least one physical processing device that executes the tunnel driver in kernel space.

A network device comprising:

• a physical routing engine that comprises a tunnel driver, stored in kernel space, that:
• receives a packet in kernel space;
• identifies metadata of the packet that indicates whether at least one firewall filter had already been correctly applied to the packet before the packet arrived at the tunnel driver, wherein the metadata of the packet comprises an Internet Protocol (IP) header of the packet;
• determines that the IP header of the packet is offset beyond a certain threshold;
• determines, based at least in part on the IP header of the packet being offset beyond the certain threshold, that the firewall filter had not been correctly applied to the packet before the packet arrived at the tunnel driver;
• and
• in response to determining that the firewall filter had not been correctly applied to the packet, invokes at least one firewall filter hook that applies at least one firewall rule on the packet in kernel space on the physical routing engine before the packet is allowed to exit kernel space on the physical routing engine;
• and
• a physical packet forwarding engine that:
• receives the packet from a remote device;
• or
• is capable of forwarding the packet to a remote device.