Link two nodes without a connection over UDP (093, design 011's first stage)

pure-serve --send OUTPUT=pure://host:port/INPUT sends an output's saved
sends to another node's --link-port with no handshake: the first packet
carries records. Keys come from the two nodes' keys (X25519, HKDF-SHA256,
AES-128-GCM), with a random run in each packet's header so no nonce
repeats across restarts; nothing is stored for them. What lasts is the
apps' own: the sender's outbox and the receiver's heard numbers
(pure_app_heard, new). The sender detects losses as RFC 9002 says, with
NewReno, and trims a send once the receiver says it stored it; the
receiver hands the owner whole records in order, which it applies from
the one after the source's last heard number, stopping at a gap, and
answers how far it stored with every acknowledgment. Stored bytes are
the bytes on the wire: an output and an input of one shape need no JSON.

server_links_udp kills the receiver, the sender, then both (-9) while
four clients buy: every saved order is applied once, with no handshake
(five runs, 10k-11k orders each). server_links_udp_lossy does it again in
a namespace of its own with the link's packets delayed, lost (3 %) and
reordered (10 %) by netem (three runs, 11k-12k orders).

1 files changed, 11 insertions, 1 deletions

diff --git a/serve/crypto.h b/serve/crypto.h
index 4919c49..b8a48fd 100644
--- a/serve/crypto.h
+++ b/serve/crypto.h
@@ -8,7 +8,7 @@
  * first time a server seals, opens a seal or connects to an https receiver
  * (serve/crypto.c): one that does none of these maps no OpenSSL, 2.3 MiB
  * less resident and 0.6 MiB less of its own. */
-enum { PURE_CRYPTO_VERSION = 2 };
+enum { PURE_CRYPTO_VERSION = 3 };
 
 typedef struct {
     unsigned version;
@@ -33,5 +33,15 @@ typedef struct {
     bool (*unseal)(PureOpener *, uint64_t n, const char *aad, const unsigned char *sealed, size_t size,
                    unsigned char *plain);
     void (*opener_free)(PureOpener *);
+    /* Links, as serve/seal.h says. */
+    bool (*link_secret)(const PureSealKey *, const unsigned char peer[PURE_SEAL_KEY], unsigned char out[32]);
+    bool (*link_derive)(const unsigned char secret[32], const unsigned char *info, size_t info_size, unsigned char *out,
+                        size_t out_size);
+    PureAead *(*aead)(const unsigned char key[PURE_AEAD_KEY]);
+    bool (*aead_seal)(PureAead *, const unsigned char nonce[PURE_AEAD_NONCE], const unsigned char *aad, size_t aad_size,
+                      const unsigned char *plain, size_t size, unsigned char *out);
+    bool (*aead_open)(PureAead *, const unsigned char nonce[PURE_AEAD_NONCE], const unsigned char *aad,
+                      size_t aad_size, const unsigned char *sealed, size_t size, unsigned char *plain);
+    void (*aead_free)(PureAead *);
 } PureCrypto;
 #endif