passt: New design and implementation with native Layer 4 sockets

This is a reimplementation, partially building on the earlier draft,
that uses L4 sockets (SOCK_DGRAM, SOCK_STREAM) instead of SOCK_RAW,
providing L4-L2 translation functionality without requiring any
security capability.

Conceptually, this follows the design presented at:
	https://gitlab.com/abologna/kubevirt-and-kvm/-/blob/master/Networking.md

The most significant novelty here comes from TCP and UDP translation
layers. In particular, the TCP state and translation logic follows
the intent of being minimalistic, without reimplementing a full TCP
stack in either direction, and synchronising as much as possible the
TCP dynamic and flows between guest and host kernel.

Another important introduction concerns addressing, port translation
and forwarding. The Layer 4 implementations now attempt to bind on
all unbound ports, in order to forward connections in a transparent
way.

While at it:
- the qemu 'tap' back-end can't be used as-is by qrap anymore,
  because of explicit checks now introduced in qemu to ensure that
  the corresponding file descriptor is actually a tap device. For
  this reason, qrap now operates on a 'socket' back-end type,
  accounting for and building the additional header reporting
  frame length

- provide a demo script that sets up namespaces, addresses and
  routes, and starts the daemon. A virtual machine started in the
  network namespace, wrapped by qrap, will now directly interface
  with passt and communicate using Layer 4 sockets provided by the
  host kernel.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/util.h b/util.h
index 8298d22..77e8d8c 100644
--- a/util.h
+++ b/util.h
@@ -1,3 +1,6 @@
 uint16_t csum_fold(uint32_t sum);
 uint16_t csum_ip4(void *buf, size_t len);
-unsigned char *ipv6_l4hdr(struct ipv6hdr *ip6h, uint8_t *proto);
+void csum_tcp4(struct iphdr *iph);
+char *ipv6_l4hdr(struct ipv6hdr *ip6h, uint8_t *proto);
+int sock_l4_add(struct ctx *c, int v, uint16_t proto, uint16_t port);
+int timespec_diff_ms(struct timespec *a, struct timespec *b);