From 56654f2cd1813d87d32695f126939bbfaad52385 Mon Sep 17 00:00:00 2001
From: Dimitri Staessens <dimitri@ouroboros.rocks>
Date: Sat, 26 Mar 2022 20:28:56 +0100
Subject: lib: Add rbuff support for FLOWPEER state

This allows setting the FLOWPEER state on a flow to signal a peer is
unresponsive.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
---
 include/ouroboros/shm_rbuff.h |  1 +
 src/lib/shm_rbuff_ll.c        | 12 +++++++++---
 src/lib/shm_rbuff_pthr.c      | 35 +++++++++++++++++++++++------------
 3 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/include/ouroboros/shm_rbuff.h b/include/ouroboros/shm_rbuff.h
index e853e487..6e77cd07 100644
--- a/include/ouroboros/shm_rbuff.h
+++ b/include/ouroboros/shm_rbuff.h
@@ -31,6 +31,7 @@
 #define ACL_RDWR     0000
 #define ACL_RDONLY   0001
 #define ACL_FLOWDOWN 0002
+#define ACL_FLOWPEER 0004
 
 struct shm_rbuff;
 
diff --git a/src/lib/shm_rbuff_ll.c b/src/lib/shm_rbuff_ll.c
index 880d81dc..2eed9b74 100644
--- a/src/lib/shm_rbuff_ll.c
+++ b/src/lib/shm_rbuff_ll.c
@@ -143,9 +143,15 @@ ssize_t shm_rbuff_read(struct shm_rbuff * rb)
 
         assert(rb);
 
-        if (shm_rbuff_empty(rb))
-                return __sync_fetch_and_add(rb->acl, 0) & ACL_FLOWDOWN ?
-                        -EFLOWDOWN : -EAGAIN;
+        if (shm_rbuff_empty(rb)) {
+                if (_sync_fetch_and_add(rb->acl, 0) & ACL_FLOWDOWN)
+                        return -EFLOWDOWN;
+
+                if (_sync_fetch_and_add(rb->acl, 0) & ACL_FLOWPEER)
+                        return -EFLOWPEER;
+
+                return -EAGAIN;
+        }
 
         ntail = RB_TAIL;
 
diff --git a/src/lib/shm_rbuff_pthr.c b/src/lib/shm_rbuff_pthr.c
index e41d31f8..657b55c4 100644
--- a/src/lib/shm_rbuff_pthr.c
+++ b/src/lib/shm_rbuff_pthr.c
@@ -141,6 +141,17 @@ int shm_rbuff_write_b(struct shm_rbuff *      rb,
         return ret;
 }
 
+static int check_rb_acl(struct shm_rbuff * rb)
+{
+        if (*rb->acl & ACL_FLOWDOWN)
+                return -EFLOWDOWN;
+
+        if (*rb->acl & ACL_FLOWPEER)
+                return -EFLOWPEER;
+
+        return -EAGAIN;
+}
+
 ssize_t shm_rbuff_read(struct shm_rbuff * rb)
 {
         ssize_t ret = 0;
@@ -155,7 +166,7 @@ ssize_t shm_rbuff_read(struct shm_rbuff * rb)
 #endif
 
         if (shm_rbuff_empty(rb)) {
-                ret = *rb->acl & ACL_FLOWDOWN ? -EFLOWDOWN : -EAGAIN;
+                ret = check_rb_acl(rb);
                 pthread_mutex_unlock(rb->lock);
                 return ret;
         }
@@ -190,9 +201,9 @@ ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
 
         pthread_cleanup_push(__cleanup_mutex_unlock, rb->lock);
 
-        while (shm_rbuff_empty(rb)
-               && (idx != -ETIMEDOUT)
-               && !(*rb->acl & ACL_FLOWDOWN)) {
+        while (shm_rbuff_empty(rb) &&
+               idx != -ETIMEDOUT &&
+               check_rb_acl(rb) == -EAGAIN) {
                 if (abstime != NULL)
                         idx = -pthread_cond_timedwait(rb->add,
                                                       rb->lock,
@@ -205,18 +216,18 @@ ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
 #endif
         }
 
-        if (idx != -ETIMEDOUT) {
-                if (*rb->acl & ACL_FLOWDOWN)
-                        idx = -EFLOWDOWN;
-                else {
-                        idx = *tail_el_ptr(rb);
-                        *rb->tail = (*rb->tail + 1) & ((SHM_RBUFF_SIZE) - 1);
-                        pthread_cond_broadcast(rb->del);
-                }
+        if (!shm_rbuff_empty(rb)) {
+                idx = *tail_el_ptr(rb);
+                *rb->tail = (*rb->tail + 1) & ((SHM_RBUFF_SIZE) - 1);
+                pthread_cond_broadcast(rb->del);
+        } else if (idx != -ETIMEDOUT) {
+                idx = check_rb_acl(rb);
         }
 
         pthread_cleanup_pop(true);
 
+        assert(idx != -EAGAIN);
+
         return idx;
 }
 
-- 
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