libcephfs_proxy: implement receiving of negotiate structure

This commit creates a function to receive a negotiation structure with
backward and forward compatibility support.

Signed-off-by: Xavi Hernandez <xhernandez@gmail.com>

diff --git a/src/libcephfs_proxy/proxy_link.c b/src/libcephfs_proxy/proxy_link.c
index ad61c2724c2928a912aead1d423cfafb981eda2c..0f3cd6588edc54189fa096b1230717494420c0f8 100644 (file)
--- a/src/libcephfs_proxy/proxy_link.c
+++ b/src/libcephfs_proxy/proxy_link.c
@@ -8,6 +8,14 @@
 #include "proxy_helpers.h"
 #include "proxy_log.h"
 
+#define DEFINE_VERSION(_num) [_num] = NEG_VERSION_SIZE(_num)
+
+static uint32_t negotiation_sizes[PROXY_LINK_NEGOTIATE_VERSION + 1] = {
+       DEFINE_VERSION(1)
+
+       /* NEG_VERSION: Add newly defined versions above this comment. */
+};
+
 static int32_t iov_length(struct iovec *iov, int32_t count)
 {
        int32_t len;
@@ -222,6 +230,73 @@ int32_t proxy_link_ctrl_recv(int32_t sd, void *data, int32_t size, int32_t type,
        return len;
 }
 
+static int32_t proxy_link_negotiate_read(proxy_link_t *link, int32_t sd,
+                                        proxy_link_negotiate_t *neg)
+{
+       char buffer[128];
+       void *ptr;
+       uint32_t size, len;
+       int32_t err;
+
+       memset(neg, 0, sizeof(proxy_link_negotiate_t));
+
+       ptr = neg;
+
+       err = proxy_link_read(link, sd, ptr, sizeof(neg->v0));
+       if (err < 0) {
+               return err;
+       }
+
+       ptr += sizeof(neg->v0);
+       size = neg->v0.size;
+
+       /* Version 0 is only used to represent legacy peers that don't use any
+        * negotiation requests. */
+       if (neg->v0.version == 0) {
+               return proxy_log(LOG_ERR, EINVAL, "Invalid negotiate version");
+       }
+
+       /* Ignore data from future versions. */
+       if (neg->v0.version > PROXY_LINK_NEGOTIATE_VERSION) {
+               neg->v0.version = PROXY_LINK_NEGOTIATE_VERSION;
+               neg->v0.size = NEG_VERSION_SIZE(PROXY_LINK_NEGOTIATE_VERSION);
+       }
+
+       if (negotiation_sizes[neg->v0.version] != neg->v0.size) {
+               return proxy_log(LOG_ERR, EINVAL,
+                                "Negotiation structure doesn't have the "
+                                "expected size");
+       }
+
+       if (neg->v0.version < neg->v0.min_version) {
+               return proxy_log(LOG_ERR, ENOTSUP,
+                                "Negotiation requires an unsupported version");
+       }
+
+       /* Read remaining negotiation data. */
+       err = proxy_link_read(link, sd, ptr, neg->v0.size - sizeof(neg->v0));
+       if (err < 0) {
+               return err;
+       }
+
+       /* Ignore any additional data belonging to unsupported negotiation
+        * structures. */
+       size -= neg->v0.size;
+       while (size > 0) {
+               len = sizeof(buffer);
+               if (len > size) {
+                       len = size;
+               }
+               err = proxy_link_read(link, sd, buffer, len);
+               if (err < 0) {
+                       return err;
+               }
+               size -= len;
+       }
+
+       return 0;
+}
+
 int32_t proxy_link_client(proxy_link_t *link, const char *path,
                          proxy_link_stop_t stop)
 {