[receiver/syslog] fixed syslog octet frame parsing (#23645)

Parse multiple syslog events from a single packet when octet framing is enabled.

.chloggen/issue-23577.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/stanza
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: adding octet counting event breaking for syslog parser
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [23577]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

pkg/stanza/operator/helper/multiline.go

@@ -56,7 +56,6 @@ func (c MultilineConfig) getSplitFunc(enc encoding.Encoding, flushAtEOF bool, fo
 		return SplitNone(maxLogSize), nil
 	case endPattern == "" && startPattern == "":
 		splitFunc, err = NewNewlineSplitFunc(enc, flushAtEOF, getTrimFunc(preserveLeadingWhitespaces, preserveTrailingWhitespaces))
-
 		if err != nil {
 			return nil, err
 		}