Revert r274494, r274712, r275955 and provide extra comments explaining
why there could appear a zero-sized mbufs in socket buffers. A proper fix would be to divorce record socket buffers and stream socket buffers, and divorce pru_send that accepts normal data from pru_send that accepts control data.
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=275968
@ -640,9 +640,6 @@ sbappendstream_locked(struct sockbuf *sb, struct mbuf *m, int flags)
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{
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SOCKBUF_LOCK_ASSERT(sb);
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if (m == NULL)
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return;
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KASSERT(m->m_nextpkt == NULL,("sbappendstream 0"));
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KASSERT(sb->sb_mb == sb->sb_lastrecord,("sbappendstream 1"));
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@ -1065,6 +1062,21 @@ sbcut_internal(struct sockbuf *sb, int len)
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m = n;
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}
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}
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/*
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* Free any zero-length mbufs from the buffer.
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* For SOCK_DGRAM sockets such mbufs represent empty records.
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* XXX: For SOCK_STREAM sockets such mbufs can appear in the buffer,
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* when sosend_generic() needs to send only control data.
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*/
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while (m && m->m_len == 0) {
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struct mbuf *n;
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sbfree(sb, m);
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n = m->m_next;
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m->m_next = mfree;
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mfree = m;
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m = n;
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}
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if (m) {
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sb->sb_mb = m;
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m->m_nextpkt = next;
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@ -1310,11 +1310,14 @@ sosend_generic(struct socket *so, struct sockaddr *addr, struct uio *uio,
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resid = 0;
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if (flags & MSG_EOR)
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top->m_flags |= M_EOR;
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} else if (resid > 0) {
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} else {
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/*
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* Copy the data from userland into a mbuf
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* chain. If no data is to be copied in,
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* a single empty mbuf is returned.
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* chain. If resid is 0, which can happen
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* only if we have control to send, then
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* a single empty mbuf is returned. This
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* is a workaround to prevent protocol send
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* methods to panic.
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*/
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top = m_uiotombuf(uio, M_WAITOK, space,
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(atomic ? max_hdr : 0),
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