Change in libosmocore[master]: ctrl: handle ECONNRESET on initial read gracefully

[Max]

Max has uploaded this change for review. ( https://gerrit.osmocom.org/11912


Change subject: ctrl: handle ECONNRESET on initial read gracefully
......................................................................

ctrl: handle ECONNRESET on initial read gracefully

When we're reading CTRL header we might get ECONNRESET when previous
message was successfully sent and the peer have already closed
connection. This is not really an error (for example script requesting
single variable have closed the connection right after reading our
answer) so just just discard the message and carry on.

Change-Id: I3cbdb3909660d605181d6923031336d296ea4340
---
M src/gsm/ipa.c
1 file changed, 9 insertions(+), 3 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/12/11912/1

diff --git a/src/gsm/ipa.c b/src/gsm/ipa.c
index 6ee003d..82ca304 100644
--- a/src/gsm/ipa.c
+++ b/src/gsm/ipa.c
@@ -548,7 +548,7 @@
  * \param[in] needed Home many bytes we have to read.
  * \returns boolean indicating whether message should be discarded.
  */
-static inline bool recv_discard_msg(int *ret, int fd, struct msgb *msg, int needed)
+static inline bool recv_discard_msg(int *ret, int fd, struct msgb *msg, int needed, bool initial)
 {
 	*ret = recv(fd, msg->tail, needed, 0);
 
@@ -563,6 +563,12 @@
 		return false;
 	}
 
+	if (errno == ECONNRESET && initial && needed == 3) {
+		/* that's initial attempt to read IPA header while connection is already closed */
+		*ret = 0;
+		return true;
+	}
+
 	/* errors indicated by -1 return value, let's save the actual error code */
 	*ret = -errno;
 	return true;
@@ -607,7 +613,7 @@
 	if (msg->l2h == NULL) {
 		/* first read our 3-byte header */
 		needed = sizeof(*hh) - msg->len;
-		discard = recv_discard_msg(&ret, fd, msg, needed);
+		discard = recv_discard_msg(&ret, fd, msg, needed, true);
 		if (discard)
 		       goto discard_msg;
 
@@ -648,7 +654,7 @@
 	needed = len - msgb_l2len(msg);
 
 	if (needed > 0) {
-		discard = recv_discard_msg(&ret, fd, msg, needed);
+		discard = recv_discard_msg(&ret, fd, msg, needed, false);
 		if (discard)
 			goto discard_msg;
 

-- 
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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I3cbdb3909660d605181d6923031336d296ea4340
Gerrit-Change-Number: 11912
Gerrit-PatchSet: 1
Gerrit-Owner: Max <msuraev at sysmocom.de>
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