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<a href="https://gitlab.com/asosedkin">Alexander Sosedkin</a> created an issue: <a href="https://gitlab.com/gnutls/gnutls/-/issues/1484">#1484</a>
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<p dir="auto" style="color: #333238; margin: 0 0 16px;" align="initial">I see the following pattern in examples (copy-pasted from <a href="https://gitlab.com/gnutls/gnutls/-/blob/master/doc/examples/ex-client-anon.c#L20" style="margin-top: 0;">doc/examples/ex-client-anon.c</a>):</p>
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<pre data-canonical-lang="c" class="code highlight js-syntax-highlight language-c" lang="c" v-pre="true" style='display: block; font-size: 0.875rem; color: #333238; line-height: 1.6em; overflow-x: auto; border-radius: 4px; position: relative; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; margin: 0 0 16px; padding: 12px; border: 1px solid #dcdcde;'><code style='font-size: 0.875rem; color: inherit; word-wrap: normal; word-break: keep-all; background-color: inherit; border-radius: 4px; white-space: pre; margin-top: 0; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; overflow-wrap: normal; padding: unset;'><span id="LC1" class="line" lang="c" style="margin-top: 0;"><span class="cp" style="margin-top: 0;">#define LOOP_CHECK(rval, cmd) \</span></span>
<span id="LC2" class="line" lang="c"><span class="cp" style="margin-top: 0;"> do { \</span></span>
<span id="LC3" class="line" lang="c"><span class="cp" style="margin-top: 0;"> rval = cmd; \</span></span>
<span id="LC4" class="line" lang="c"><span class="cp" style="margin-top: 0;"> } while(rval == GNUTLS_E_AGAIN || rval == GNUTLS_E_INTERRUPTED); \</span></span>
<span id="LC5" class="line" lang="c"><span class="cp" style="margin-top: 0;"> assert(rval >= 0)</span></span>
<span id="LC6" class="line" lang="c"><span class="cp" style="margin-top: 0;">#define MAX_BUF 1024</span></span>
<span id="LC7" class="line" lang="c"><span class="cp" style="margin-top: 0;">#define MSG "GET / HTTP/1.0\r\n\r\n"</span></span>
<span id="LC8" class="line" lang="c"><span class="p" style="margin-top: 0;">...</span></span>
<span id="LC9" class="line" lang="c"><span class="n" style="margin-top: 0;">LOOP_CHECK</span><span class="p">(</span><span class="n">ret</span><span class="p">,</span> <span class="n">gnutls_record_send</span><span class="p">(</span><span class="n">session</span><span class="p">,</span> <span class="n">MSG</span><span class="p">,</span> <span class="n">strlen</span><span class="p">(</span><span class="n">MSG</span><span class="p">)));</span> <span class="c1">// no other loop, no nothing</span></span></code></pre>
<copy-code></copy-code>
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<p dir="auto" style="color: #333238; margin: 0 0 16px;" align="initial">If gnutls_record_send does a "short write", writing the buffer out only partially and returning less than <code style='font-size: 0.875rem; color: #1f1e24; word-wrap: break-word; background-color: #ececef; border-radius: 4px; margin-top: 0; font-weight: inherit; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 2px 4px;'>strlen(MSG)</code>, the request won't be sent in a complete form and the example would hang.
The problematic short write handling holds true for other examples, say, echo server.</p>
<p dir="auto" style="color: #333238; margin: 0 0 16px;" align="initial">I believe we should fix the examples to handle short writes correctly, ideally in a coordinated, uniform manner.</p>
<p dir="auto" style="color: #333238; margin: 0 0 16px;" align="initial">Alternative options include:</p>
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<li style="margin-top: 0; line-height: 1.6em; margin-left: 25px; padding-left: 3px;">Modify <code style='font-size: 0.875rem; color: #1f1e24; word-wrap: break-word; background-color: #ececef; border-radius: 4px; margin-top: 0; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 2px 4px;'>gnutls_record_send</code> to handle short writes correctly. This sounds like it even preserves the API guarantees, but I'm not sure it won't change behaviour non-trivially when non-blocking sockets are used, say, by introducing a performance regression.</li>
<li style="line-height: 1.6em; margin-left: 25px; padding-left: 3px;">Implement additional, simplified version of <code style='font-size: 0.875rem; color: #1f1e24; word-wrap: break-word; background-color: #ececef; border-radius: 4px; margin-top: 0; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 2px 4px;'>gnutls_record_send</code> that'd handle short writes transparently, possibly also <code style='font-size: 0.875rem; color: #1f1e24; word-wrap: break-word; background-color: #ececef; border-radius: 4px; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 2px 4px;'>E_AGAIN</code>/<code style='font-size: 0.875rem; color: #1f1e24; word-wrap: break-word; background-color: #ececef; border-radius: 4px; font-family: var(--default-mono-font, "Menlo"),"DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 2px 4px;'>E_INTERRUPTED</code>.</li>
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